This acid is sometimes called "oil of vitriol," and when pure should be almost, or quite colorless, and should be kept in a strong bottle with a close fitting glass stop¬per, as the particles of dust, wood, cork, or other organic matter quickly imparts a dark, brownish color to it.
When diluting this acid it is highly important that the acid shoidd be poured very slowly into the water, and never the reverse. Both the acid and water should also be quite cold, as great heat is evolved upon mixing them. Shoidd a quantity of hot watet be suddenly added to an equal amount of sulphuric acid, a violent explosion is almost cer¬tain to take place.
ASİT VE ALKALİ İLE DAĞLAMA (Pickling) İLE DAĞLAMA NASIL YAPILIR?
ASİT VE ALKALİ İLE DAĞLAMA (Pickling)
Eğer demir içeren bir metal ile çalışıyorsanız bazı durumlarda metal yüzeyinde kötü şekilde oksitlenme meydana gelmiş olabilir. Temizlenecek metalin yüzeyi gres veya yağ ile kirlenmiş ve aynı zamanda lekeler, pasdan kaynaklanan renk bozuklukları mevcut olabilir. Asitle dağlamanın amacı alkali temizleme banyosunda giderilemeyecek olan bu pas ve lekeleri ortadan kaldırmaktır.
Prensipte asitle dağlama banyosunda mevcut bulunan asit, pası veya oksit tabakasını metale zarar vermeden çözer, uygulamada ise iyice temizlenmiş olan metalde asidin az da olsa bir tahribata yol açması sözkonusudur. Asitle dağlama çözeltisinde bulunan ve inhibitör olarak bilinen maddeler yardımı ile temizlenmiş metal yüzeye asidin etkisi minimum düzeyde tutulur. 10
Herhangi bir metal asitle dağlamadan veya aside daldırılmadan önce yüzeyindeki kirler, gres vb. giderilmelidir. Bu nedenle aside daldırmadan önce yağ alma ve/veya elektrikli yağ alma uygulanmalıdır. Gres bulaşmış veya kirli bir metal parçaya uniform olarak asitle dağlama uygulanamaz çünkü gres asidin yüzeye etki etmesini engeller.
Aside daldırmanın veya asitle dağlamanın ikinci bir kullanımı da zaten temizlenmiş olan yüzeye metal kaplamanın daha iyi yapışması için asitle oymak (etching) amacıyla yapılmasıdır. Bu durumda kendimizi oksidi ve pulları gidermekle sınırlamış oluruz.
NOT : Yakında değişik kimyasallar ve bileşiklerle çalışmaya başlayacaksınız. Bunlardan bazıları doğru kullanılmadığı takdirde zehirli ve tehlikeli olabilir. Eğer bir bileşik veya kimyasalı kullanma talimatlarına uyarak ve özelliklerine dikkat ederek kullanırsanız herhangi bir tehlikesi yoktur. Öte yandan eğer dikkatsiz davranır ve talimatlara uymazsanız kendinizi ve diğerlerini zor durumda bırakabilirsiniz. Bir örnek vermek gerekirse, borik asit göz yıkamasında kullanılacak kadar yumuşak bir asittir ve üzerinde zehirli olduğuna dair bir etiket yoktur fakat yutulduğu takdirde öldürücü bir zehirdir. Eğer talimatlara uyarsanız ve dahice (!) işler yapmaya kalkışmazsanız kötü bir durumla karşılaşmazsınız.
DENEY 2 :
1. Yüzeyi paslı küçük bir parça demir veya çelik şerit alıp üzerine mısır yağı benzeri herhangi bir bitkisel yağ veya margarin sürün. Şeridi içerisinde 1 ölçü hidroklorik asit (muriatik asit) ve 3 ölçü su bulunan bir behere veya geniş ağızlı bir su bardağına daldırıp meydana gelen etkiyi gözlemleyin.
NOT : Hidroklorik asit kuvvetli bir asittir. Behere koyarken dikkatli olun, elbisenize veya vücudunuza sıçramamasına özen gösterin. Eğer çıplak derinize temas ederse hemen bol suyla yıkayın. Bu genellikle yanıkları önler fakat emin olmak için aside maruz kalan kısma bikarbonatlı soda pastası sürün ve durulayın.
2. Şimdi aynı şeridi üzerinde asit kalmayıncaya kadar birkaç kez temiz suyla yıkayın 2 çorba kaşığı trisodyum fosfat (boya malzemeleri satıcılarından temin edebilirsiniz), 3 çorba kaşığı sodyum karbonat (çamaşır sodası) ve 473 ml. suyla hazırladığınız sıcak çözeltiye daldırın. Gres çıkana kadar şeridi karıştırarak çözeltiye daldırıp çıkarın.
3. Şeridi hidroklorik aside daldırın ve ne olduğunu gözlemleyin. Şeridi 1 dakika kadar asitte tuttuktan sonra çıkarıp durulayın. İlk seferinde ve ikincide neler olduğunu karşılaştırın. Yüzeydeki oksitlenmeyi çıkarmak için önce gres kalıntıları temizlenmelidir. Deney bittikten sonra aside dikkatlice kireçtaşı parçaları (kalsiyum karbonat) veya sodyum karbonat (çamaşır sodası) ekleyin ve köpürtünün bitmesini bekleyip atığı bol suyla boşaltın.
Asitle dağlama (pickling) genellikle pulların, oksitlenmenin ve pasın giderilmesini içerir. Aside daldırma ise genellikle hafif oksitlenmiş ve kararmış film tabakanın giderilmesi, alkali film tabakasının nötralize edilmesi, asitle oyulması ve kaplama öncesi metalin aktifleştirilmesi için kullanılır. Her ikisi de birbirinin yerine kullanılabilir fakat genelde dayanıklı veya hassas işlerde dağlamaya başvurulur. Genellikle asitle dağlama yakından yapılır fakat gerçek kaplamacılıkta aside daldırma yer kaplar.
Şimdi bazı asitle dağlama (pickling), aside daldırma ve parlak daldırma reçeteleri vereceğiz. Bunlar sizin ihtiyaçlarınıza cevap verebilecekler arasından seçilmiş birkaç tanesidir. Değişik kaynaklarda daha fazlasını bulabilirsiniz. Satıcılar da size yardımcı olabilirler.
Kimyasallar hakkında not : Bahsedilen bütün asitler konsantre asittir. Sülfürik asidin bomesi 66° olup %93 H2SO4 içerir. Nitrik asidin bomesi 42° dir ve %67 HNO3 içerir. Hidroklorik asidin (Muriatik asit) bomesi ise 20° dir ve %35 HCl içerir.
ÖZEL UYARI : ASİTLERLE ÖZELLİKLE DE SÜLFÜRİK ASİTLE ÇALIŞIRKEN DAİMA ASİDİ SUYA EKLEYİN. ASLA ASİDİN ÜZERİNE SU DÖKMEYİN VE DAHA ÖNCEDEN SÖZÜ EDİLEN GÜVENLİK KURALLARINI UNUTMAYIN (KORUYUCU GÖZLÜK VE LASTİK ELDİVEN KULLANIN)!
DEMİR İÇEREN METALLERİN ASİTLE TEMİZLENMESİ
Hafif Pullu ve Paslı
Reçete
1. Sülfürik asit 237 ml.
2. Santomerse S 0,28 gr.
3. İnhibitör 0,28 gr.
4. Su 3549 ml.
Çalışma Koşulları
Malzemeleri karıştırma sırası : 4, 1, 2, 3
Tank : Kurşun
Sıcaklık : 66 °C
Isıtma : Kurşun buhar bobini ile
Aşırı Pullu ve Kuru Paslı
Reçete
1. Sülfürik asit 946 ml.
2. Santomerse S 3 gr.
3. İnhibitör 3 gr.
4. Su 2839 ml.
Çalışma Koşulları
Malzemeleri karıştırma sırası : 4, 1, 2, 3
Sıcaklık : Oda sıcaklığından 66 °C’ ye kadar
Tank : Seramik veya bir Haveg ya da cam epoksi tank ve Pyrex veya titanyum ısıtma bobini kullanın.
Demir Döküm
Reçete
1. Hidroklorik asit 473 ml.
2. Hidroflorik asit 59 ml.
3. Su 3312 ml.
Çalışma Koşulları
Malzemeleri karıştırma sırası : 3, 2, 1
Tank : Kurşun veya daha iyisi karbon tuğlalardan yapılmış KARBATE ısıtma bobinli tank
Sıcaklık : 60 °C
NOT : HİDROFLORİK ASİTLE ÇALIŞIRKEN ÇOK DİKKATLİ OLUN! ÇOK KÖTÜ YANIKLARA SEBEP OLUR VE KOLAYLIKLA PATLAYABİLİR. BUNA İLAVETEN CAMI TAHRİP EDER.
Pirinç Üzerindeki Yanık Pulların Asitle Temizlenmesi
Reçete
1. Su 2839 ml.
2. Sülfürik asit 946 ml.
Çalışma Koşulları
Sıcaklık : 82 °C
Tank : Kurşun tank ve kurşun ısıtma bobini
NOT: Bu reçete aynı zamanda tavlanmış veya lehimlenmiş ve kumlu döküm pirinç ve bakır için de iyidir. Pullar gidene veya azalana kadar bu karışıma daldırılır, sonra soğuk suda durulanır, ardından aşağıda verilmiş olan Fire Off Daldırmaya nakledilir.
Yanıkların Asitle Temizlenmesi
Reçete
1. Sülfürik asit 946 ml
2. Nitrik asit 473 ml.
3. Su 2366 ml.
Çalışma Koşulları
Sıcaklık : Oda sıcaklığı
Tank : Toprak kap
Daldırma süresi : 5 – 30 saniye
NOT: Pirinç pürüzsüz ve gölgeli bir görünüş alana kadar tutun, sonra çıkarın ve parlak daldırmadan önce durulayın. İş çözeltideyken karıştırma uygulayın.
PARLAK DALDIRMA ve asitle dağlama (pickling) genellikle asit odaları olarak bilinen ve kaplama yapılan yerden ayrılmış bir bölümde veya odada yapılır. Bu odaların döşemesi aside dayanıklıdır ve asit buharları solunmadan önce ortamdan uzaklaştırılacak şekilde bir havalandırma sistemi bulunur.
Çeşitli daldırma çözeltileri hazırlamak için asitlerle çalışmanız gerektiğinde eğer talimatları doğru şekilde uygularsanız bir tehlike sözkonusu değildir. Konsantre asitler genellikle 30-45 litrelik aside dayanıklı varillerle gelir. Aside dayanıklı bir asit pompası veya sallama düzeneği 11 ile boşaltılır. Asitlerle çalışırken lastik eldiven ve lastik önlük kullanmalısınız. Koruyucu gözlük de kesinlikle kullanımalıdır.
Geçmişte parlak daldırma ve asitle dağlamada kuvvetli asitlerin kullanımına bel bağlandığı halde son gelişmelerle bu uygulamaların bazıları demode hale gelmiştir.
Günümüzde piyasada parlak daldırma ve asitle dağlamada kullanılan kuru tuzlar ve bileşikler 12 bulunmaktadır. Bu malzemeler konsantre asitlere göre daha az tehlikelidir. (Yine de bu maddelerle çalışırken güvenlik gözlüğü kullanılmalıdır). Bu tip bir asitle dağlama kimyasalına örnek olarak TROXIDE ve FERRISUL verilebilir. Bunlar çeşitli aside daldırma ve asitle dağlama işlemlerinde kullanılırlar.
Eğer asitle çalışmalara yeni başlamışsanız ve deneyiminiz yoksa daha önce deneylerde bahsedilenler dışında başka bir asit reçetesini hazırlamamanızı öneririm. Sebebi ise önce temizleme işlemleri hakkında net bir fikre olmanızı sağlamaktır. Tehlikeli kimyasallarla çalışmaya başlamadan önce daha az tehlikeli olanlarla çalışmanız daha iyi olacaktır. Örnek olarak verilen aşağıdaki temizleme çözeltilerini ve düzenekleri hazırlayıp çalışabilirsiniz.
DENEY 3 : Aşağıdaki elektrikli yağ alma çözeltisini hazırlayın.
1. Su 3785 ml
2. Trisodyum fosfat 85 gr.
3. Sodyum karbonat (çamaşır sodası) 56,7 gr.
4. Fildişi rengi granül 28,3 gr.
Suyu 4 litrelik cam behere koyun. Malzemeleri verilme sıralarına göre çözün. Beherin içine iki ince çelik levha yerleştirin (paslanmaz olması tercih edilir) ve bunları #18 bakır kablosuyla birbirine bağlayın ve dışarıdan şekilde gösterildiği gibi şalter bağlantısı yapın. Bu size anodik veya katodik temizleme yapabilme imkanı sağlar. Yağ alma çözeltisini elektrikli ısıtıcının üstünde ısıtın ve kaynama noktasına yakın bir sıcaklıkta sabit tutun. Kullanmadığınız zaman kapağını kapatın.
Denemek amacıyla bakır yaprağı, pirinç, çinko veya galvanizli sac, aluminyum ve çelik şeritler kullanın. Her metalden en az iki şerit alın ve bir tanesini bitkisel yağ veya yemeklik yağ ile, diğerini mineral gresi veya yağı ile yağlayın. Yağ almadan sonra durulama için akarsu kullanın. Önce #18 kabloyu şeride bağlayıp şalter direkt pozisyonundayken katodik temizlemeyi deneyin. Bu şekilde bir dakika akım uygulayın. Temiz akarsuda durulayın. Su ayrışma testi uygulayın (Temizlik için uygulanan testler bölümüne bakın). Parçayı kurutun, üzerine tekrar aynı banyo kirinden sürdükten sonra anodik temizleme uygulamak için şalteri ters konuma getirin. Bir dakika boyunca temizleyip temiz suda durulayın. Hangi metallerin doğru akımda, hangilerinin ters akımda lekelendiğine dikkat edin ve hangi metodla daha iyi temizlendiğini gözlemleyin. Yağ almaya 3 Volt gerilim uygulandığındaki etkisini deneyin. Üç voltu iki adet kuru pil (2 x 1,5 Volt) kullanarak elde edebilirsiniz. Düşük gerilimde anot ve katottaki gaz çıkışındaki değişikliğe dikkat edin.
DENEY 4 : Aşağıda verilmiş olan pirinç ve bakır için kuru tuz tipi parlak daldırma çözeltisini hazırlayın.
1. Su 3785 ml
2. Sodyum nitrat 907 gr.
3. Sodyum bisülfat 1134 gr.
4. Sodyum bikromat 907 gr.
5. Demir sülfat 227 gr.
Suyu 60 °C’ ye ısıtın ve tuzları verilen sırayla çözün. Çözelti soğuduğunda bir miktar tuz dibe çökelecektir. Çözeltiyi 4 litrelik cam behere koyun. Beheri paslanmaz çelikten bir kabın içine yerleştirin. Böylelikle eğer beher kırılırsa çözelti çelik kabın içinde kalacaktır. Sıcaklığı kontrol etmek için bir termometre kullanın.
Şimdi temizlenmiş bakır ve pirinç şeritlerden bazılarını test etmek için alın. Temiz bir pirinç şeridi parlak daldırma çözeltisine daldırın ve karıştırma uygulayarak bir dakika tutun. Yüzeyini gözlemleyin ve hızlı bir şekilde çıkarıp soğuk suda çabucak durulayın. Bir süreliğine çözeltiye geri koyun. Bu ilave süre boyunca hiçbir etki olmayacaktır. Sıcaklığı 82 °C’ ye çıkarın ve bir başka pirinç şerit kullanın. Sıcaklığın artırılmasının etkisine dikkat edin. Genelde banyo ne kadar sıcak olursa işlem de o kadar kısa sürer. Bu banyo yukarıdaki listede verilmiş tuzlarla hazırlanır ve çok az da serbest asit içerir fakat ısıtıldığında tuzlar çok daha fazla iyonize olurlar (Ders 2’ ye bakın), çözeltide hidrojen iyonları oluşur, pirinç ve bakıra etki edinceye kadar çözelti gittikçe daha fazla asidik hale gelir.
NOT: BU DENEYİ SADECE KROMATLAMA TESİSİNİZ VARSA DENEYİN. KROM İÇEREN ATIKLAR DOĞRUDAN KANALİZASYONA VERİLEMEZLER.
Şimdi parlak daldırmanın bazı detaylarını ele almaya hazırız.
Eğer demir içeren bir metal ile çalışıyorsanız bazı durumlarda metal yüzeyinde kötü şekilde oksitlenme meydana gelmiş olabilir. Temizlenecek metalin yüzeyi gres veya yağ ile kirlenmiş ve aynı zamanda lekeler, pasdan kaynaklanan renk bozuklukları mevcut olabilir. Asitle dağlamanın amacı alkali temizleme banyosunda giderilemeyecek olan bu pas ve lekeleri ortadan kaldırmaktır.
Prensipte asitle dağlama banyosunda mevcut bulunan asit, pası veya oksit tabakasını metale zarar vermeden çözer, uygulamada ise iyice temizlenmiş olan metalde asidin az da olsa bir tahribata yol açması sözkonusudur. Asitle dağlama çözeltisinde bulunan ve inhibitör olarak bilinen maddeler yardımı ile temizlenmiş metal yüzeye asidin etkisi minimum düzeyde tutulur. 10
Herhangi bir metal asitle dağlamadan veya aside daldırılmadan önce yüzeyindeki kirler, gres vb. giderilmelidir. Bu nedenle aside daldırmadan önce yağ alma ve/veya elektrikli yağ alma uygulanmalıdır. Gres bulaşmış veya kirli bir metal parçaya uniform olarak asitle dağlama uygulanamaz çünkü gres asidin yüzeye etki etmesini engeller.
Aside daldırmanın veya asitle dağlamanın ikinci bir kullanımı da zaten temizlenmiş olan yüzeye metal kaplamanın daha iyi yapışması için asitle oymak (etching) amacıyla yapılmasıdır. Bu durumda kendimizi oksidi ve pulları gidermekle sınırlamış oluruz.
NOT : Yakında değişik kimyasallar ve bileşiklerle çalışmaya başlayacaksınız. Bunlardan bazıları doğru kullanılmadığı takdirde zehirli ve tehlikeli olabilir. Eğer bir bileşik veya kimyasalı kullanma talimatlarına uyarak ve özelliklerine dikkat ederek kullanırsanız herhangi bir tehlikesi yoktur. Öte yandan eğer dikkatsiz davranır ve talimatlara uymazsanız kendinizi ve diğerlerini zor durumda bırakabilirsiniz. Bir örnek vermek gerekirse, borik asit göz yıkamasında kullanılacak kadar yumuşak bir asittir ve üzerinde zehirli olduğuna dair bir etiket yoktur fakat yutulduğu takdirde öldürücü bir zehirdir. Eğer talimatlara uyarsanız ve dahice (!) işler yapmaya kalkışmazsanız kötü bir durumla karşılaşmazsınız.
DENEY 2 :
1. Yüzeyi paslı küçük bir parça demir veya çelik şerit alıp üzerine mısır yağı benzeri herhangi bir bitkisel yağ veya margarin sürün. Şeridi içerisinde 1 ölçü hidroklorik asit (muriatik asit) ve 3 ölçü su bulunan bir behere veya geniş ağızlı bir su bardağına daldırıp meydana gelen etkiyi gözlemleyin.
NOT : Hidroklorik asit kuvvetli bir asittir. Behere koyarken dikkatli olun, elbisenize veya vücudunuza sıçramamasına özen gösterin. Eğer çıplak derinize temas ederse hemen bol suyla yıkayın. Bu genellikle yanıkları önler fakat emin olmak için aside maruz kalan kısma bikarbonatlı soda pastası sürün ve durulayın.
2. Şimdi aynı şeridi üzerinde asit kalmayıncaya kadar birkaç kez temiz suyla yıkayın 2 çorba kaşığı trisodyum fosfat (boya malzemeleri satıcılarından temin edebilirsiniz), 3 çorba kaşığı sodyum karbonat (çamaşır sodası) ve 473 ml. suyla hazırladığınız sıcak çözeltiye daldırın. Gres çıkana kadar şeridi karıştırarak çözeltiye daldırıp çıkarın.
3. Şeridi hidroklorik aside daldırın ve ne olduğunu gözlemleyin. Şeridi 1 dakika kadar asitte tuttuktan sonra çıkarıp durulayın. İlk seferinde ve ikincide neler olduğunu karşılaştırın. Yüzeydeki oksitlenmeyi çıkarmak için önce gres kalıntıları temizlenmelidir. Deney bittikten sonra aside dikkatlice kireçtaşı parçaları (kalsiyum karbonat) veya sodyum karbonat (çamaşır sodası) ekleyin ve köpürtünün bitmesini bekleyip atığı bol suyla boşaltın.
Asitle dağlama (pickling) genellikle pulların, oksitlenmenin ve pasın giderilmesini içerir. Aside daldırma ise genellikle hafif oksitlenmiş ve kararmış film tabakanın giderilmesi, alkali film tabakasının nötralize edilmesi, asitle oyulması ve kaplama öncesi metalin aktifleştirilmesi için kullanılır. Her ikisi de birbirinin yerine kullanılabilir fakat genelde dayanıklı veya hassas işlerde dağlamaya başvurulur. Genellikle asitle dağlama yakından yapılır fakat gerçek kaplamacılıkta aside daldırma yer kaplar.
Şimdi bazı asitle dağlama (pickling), aside daldırma ve parlak daldırma reçeteleri vereceğiz. Bunlar sizin ihtiyaçlarınıza cevap verebilecekler arasından seçilmiş birkaç tanesidir. Değişik kaynaklarda daha fazlasını bulabilirsiniz. Satıcılar da size yardımcı olabilirler.
Kimyasallar hakkında not : Bahsedilen bütün asitler konsantre asittir. Sülfürik asidin bomesi 66° olup %93 H2SO4 içerir. Nitrik asidin bomesi 42° dir ve %67 HNO3 içerir. Hidroklorik asidin (Muriatik asit) bomesi ise 20° dir ve %35 HCl içerir.
ÖZEL UYARI : ASİTLERLE ÖZELLİKLE DE SÜLFÜRİK ASİTLE ÇALIŞIRKEN DAİMA ASİDİ SUYA EKLEYİN. ASLA ASİDİN ÜZERİNE SU DÖKMEYİN VE DAHA ÖNCEDEN SÖZÜ EDİLEN GÜVENLİK KURALLARINI UNUTMAYIN (KORUYUCU GÖZLÜK VE LASTİK ELDİVEN KULLANIN)!
DEMİR İÇEREN METALLERİN ASİTLE TEMİZLENMESİ
Hafif Pullu ve Paslı
Reçete
1. Sülfürik asit 237 ml.
2. Santomerse S 0,28 gr.
3. İnhibitör 0,28 gr.
4. Su 3549 ml.
Çalışma Koşulları
Malzemeleri karıştırma sırası : 4, 1, 2, 3
Tank : Kurşun
Sıcaklık : 66 °C
Isıtma : Kurşun buhar bobini ile
Aşırı Pullu ve Kuru Paslı
Reçete
1. Sülfürik asit 946 ml.
2. Santomerse S 3 gr.
3. İnhibitör 3 gr.
4. Su 2839 ml.
Çalışma Koşulları
Malzemeleri karıştırma sırası : 4, 1, 2, 3
Sıcaklık : Oda sıcaklığından 66 °C’ ye kadar
Tank : Seramik veya bir Haveg ya da cam epoksi tank ve Pyrex veya titanyum ısıtma bobini kullanın.
Demir Döküm
Reçete
1. Hidroklorik asit 473 ml.
2. Hidroflorik asit 59 ml.
3. Su 3312 ml.
Çalışma Koşulları
Malzemeleri karıştırma sırası : 3, 2, 1
Tank : Kurşun veya daha iyisi karbon tuğlalardan yapılmış KARBATE ısıtma bobinli tank
Sıcaklık : 60 °C
NOT : HİDROFLORİK ASİTLE ÇALIŞIRKEN ÇOK DİKKATLİ OLUN! ÇOK KÖTÜ YANIKLARA SEBEP OLUR VE KOLAYLIKLA PATLAYABİLİR. BUNA İLAVETEN CAMI TAHRİP EDER.
Pirinç Üzerindeki Yanık Pulların Asitle Temizlenmesi
Reçete
1. Su 2839 ml.
2. Sülfürik asit 946 ml.
Çalışma Koşulları
Sıcaklık : 82 °C
Tank : Kurşun tank ve kurşun ısıtma bobini
NOT: Bu reçete aynı zamanda tavlanmış veya lehimlenmiş ve kumlu döküm pirinç ve bakır için de iyidir. Pullar gidene veya azalana kadar bu karışıma daldırılır, sonra soğuk suda durulanır, ardından aşağıda verilmiş olan Fire Off Daldırmaya nakledilir.
Yanıkların Asitle Temizlenmesi
Reçete
1. Sülfürik asit 946 ml
2. Nitrik asit 473 ml.
3. Su 2366 ml.
Çalışma Koşulları
Sıcaklık : Oda sıcaklığı
Tank : Toprak kap
Daldırma süresi : 5 – 30 saniye
NOT: Pirinç pürüzsüz ve gölgeli bir görünüş alana kadar tutun, sonra çıkarın ve parlak daldırmadan önce durulayın. İş çözeltideyken karıştırma uygulayın.
PARLAK DALDIRMA ve asitle dağlama (pickling) genellikle asit odaları olarak bilinen ve kaplama yapılan yerden ayrılmış bir bölümde veya odada yapılır. Bu odaların döşemesi aside dayanıklıdır ve asit buharları solunmadan önce ortamdan uzaklaştırılacak şekilde bir havalandırma sistemi bulunur.
Çeşitli daldırma çözeltileri hazırlamak için asitlerle çalışmanız gerektiğinde eğer talimatları doğru şekilde uygularsanız bir tehlike sözkonusu değildir. Konsantre asitler genellikle 30-45 litrelik aside dayanıklı varillerle gelir. Aside dayanıklı bir asit pompası veya sallama düzeneği 11 ile boşaltılır. Asitlerle çalışırken lastik eldiven ve lastik önlük kullanmalısınız. Koruyucu gözlük de kesinlikle kullanımalıdır.
Geçmişte parlak daldırma ve asitle dağlamada kuvvetli asitlerin kullanımına bel bağlandığı halde son gelişmelerle bu uygulamaların bazıları demode hale gelmiştir.
Günümüzde piyasada parlak daldırma ve asitle dağlamada kullanılan kuru tuzlar ve bileşikler 12 bulunmaktadır. Bu malzemeler konsantre asitlere göre daha az tehlikelidir. (Yine de bu maddelerle çalışırken güvenlik gözlüğü kullanılmalıdır). Bu tip bir asitle dağlama kimyasalına örnek olarak TROXIDE ve FERRISUL verilebilir. Bunlar çeşitli aside daldırma ve asitle dağlama işlemlerinde kullanılırlar.
Eğer asitle çalışmalara yeni başlamışsanız ve deneyiminiz yoksa daha önce deneylerde bahsedilenler dışında başka bir asit reçetesini hazırlamamanızı öneririm. Sebebi ise önce temizleme işlemleri hakkında net bir fikre olmanızı sağlamaktır. Tehlikeli kimyasallarla çalışmaya başlamadan önce daha az tehlikeli olanlarla çalışmanız daha iyi olacaktır. Örnek olarak verilen aşağıdaki temizleme çözeltilerini ve düzenekleri hazırlayıp çalışabilirsiniz.
DENEY 3 : Aşağıdaki elektrikli yağ alma çözeltisini hazırlayın.
1. Su 3785 ml
2. Trisodyum fosfat 85 gr.
3. Sodyum karbonat (çamaşır sodası) 56,7 gr.
4. Fildişi rengi granül 28,3 gr.
Suyu 4 litrelik cam behere koyun. Malzemeleri verilme sıralarına göre çözün. Beherin içine iki ince çelik levha yerleştirin (paslanmaz olması tercih edilir) ve bunları #18 bakır kablosuyla birbirine bağlayın ve dışarıdan şekilde gösterildiği gibi şalter bağlantısı yapın. Bu size anodik veya katodik temizleme yapabilme imkanı sağlar. Yağ alma çözeltisini elektrikli ısıtıcının üstünde ısıtın ve kaynama noktasına yakın bir sıcaklıkta sabit tutun. Kullanmadığınız zaman kapağını kapatın.
Denemek amacıyla bakır yaprağı, pirinç, çinko veya galvanizli sac, aluminyum ve çelik şeritler kullanın. Her metalden en az iki şerit alın ve bir tanesini bitkisel yağ veya yemeklik yağ ile, diğerini mineral gresi veya yağı ile yağlayın. Yağ almadan sonra durulama için akarsu kullanın. Önce #18 kabloyu şeride bağlayıp şalter direkt pozisyonundayken katodik temizlemeyi deneyin. Bu şekilde bir dakika akım uygulayın. Temiz akarsuda durulayın. Su ayrışma testi uygulayın (Temizlik için uygulanan testler bölümüne bakın). Parçayı kurutun, üzerine tekrar aynı banyo kirinden sürdükten sonra anodik temizleme uygulamak için şalteri ters konuma getirin. Bir dakika boyunca temizleyip temiz suda durulayın. Hangi metallerin doğru akımda, hangilerinin ters akımda lekelendiğine dikkat edin ve hangi metodla daha iyi temizlendiğini gözlemleyin. Yağ almaya 3 Volt gerilim uygulandığındaki etkisini deneyin. Üç voltu iki adet kuru pil (2 x 1,5 Volt) kullanarak elde edebilirsiniz. Düşük gerilimde anot ve katottaki gaz çıkışındaki değişikliğe dikkat edin.
DENEY 4 : Aşağıda verilmiş olan pirinç ve bakır için kuru tuz tipi parlak daldırma çözeltisini hazırlayın.
1. Su 3785 ml
2. Sodyum nitrat 907 gr.
3. Sodyum bisülfat 1134 gr.
4. Sodyum bikromat 907 gr.
5. Demir sülfat 227 gr.
Suyu 60 °C’ ye ısıtın ve tuzları verilen sırayla çözün. Çözelti soğuduğunda bir miktar tuz dibe çökelecektir. Çözeltiyi 4 litrelik cam behere koyun. Beheri paslanmaz çelikten bir kabın içine yerleştirin. Böylelikle eğer beher kırılırsa çözelti çelik kabın içinde kalacaktır. Sıcaklığı kontrol etmek için bir termometre kullanın.
Şimdi temizlenmiş bakır ve pirinç şeritlerden bazılarını test etmek için alın. Temiz bir pirinç şeridi parlak daldırma çözeltisine daldırın ve karıştırma uygulayarak bir dakika tutun. Yüzeyini gözlemleyin ve hızlı bir şekilde çıkarıp soğuk suda çabucak durulayın. Bir süreliğine çözeltiye geri koyun. Bu ilave süre boyunca hiçbir etki olmayacaktır. Sıcaklığı 82 °C’ ye çıkarın ve bir başka pirinç şerit kullanın. Sıcaklığın artırılmasının etkisine dikkat edin. Genelde banyo ne kadar sıcak olursa işlem de o kadar kısa sürer. Bu banyo yukarıdaki listede verilmiş tuzlarla hazırlanır ve çok az da serbest asit içerir fakat ısıtıldığında tuzlar çok daha fazla iyonize olurlar (Ders 2’ ye bakın), çözeltide hidrojen iyonları oluşur, pirinç ve bakıra etki edinceye kadar çözelti gittikçe daha fazla asidik hale gelir.
NOT: BU DENEYİ SADECE KROMATLAMA TESİSİNİZ VARSA DENEYİN. KROM İÇEREN ATIKLAR DOĞRUDAN KANALİZASYONA VERİLEMEZLER.
Şimdi parlak daldırmanın bazı detaylarını ele almaya hazırız.
AQUA REGIA
AQUA REGIA
This acid is a mixture of nitric and hydro-chloric acids in the proportion of one volume of nitric and from one to three parts of hydro-chloric acids, the strongest and best results being obtained when the propor¬tions are about one of nitric and two of hydro¬chloric acids. It should not be prepared until required for immediate use, as it deteriorates rapidly.
This acid is a mixture of nitric and hydro-chloric acids in the proportion of one volume of nitric and from one to three parts of hydro-chloric acids, the strongest and best results being obtained when the propor¬tions are about one of nitric and two of hydro¬chloric acids. It should not be prepared until required for immediate use, as it deteriorates rapidly.
HYDROCHLORIC ACID
HYDROCHLORIC ACID
This acid is best known as muriatic acid, and when pure should
be almost colorless, and of a specific gravity not
less than 1200 This acid is formed by the
chemical union, or combination of hydrogen
and chlorine. Hence the name hydrochloric
acid.
This acid is best known as muriatic acid, and when pure should
be almost colorless, and of a specific gravity not
less than 1200 This acid is formed by the
chemical union, or combination of hydrogen
and chlorine. Hence the name hydrochloric
acid.
WHAT İS THE NITRIC ACID?
NITRIC ACID
This acid is sometimes aqua fortis. Only the best and strongest acid should be used for dissolving silver to form the nitrate of silver. A small portion of it largely diluted with pure distilled water should form no cloud upon the addition of a drop of a strong solution of nitrate of silver. It should be kept in strong well stoppered bottles, in a dark, cool and dry place.
Care should be taken not to inhale any of the fumes that arise from the acid.
Should a drop of this or any other acid fall upon the clothes, apply freely and at once, a quantity of diluted aqua ammonia.
This acid is sometimes aqua fortis. Only the best and strongest acid should be used for dissolving silver to form the nitrate of silver. A small portion of it largely diluted with pure distilled water should form no cloud upon the addition of a drop of a strong solution of nitrate of silver. It should be kept in strong well stoppered bottles, in a dark, cool and dry place.
Care should be taken not to inhale any of the fumes that arise from the acid.
Should a drop of this or any other acid fall upon the clothes, apply freely and at once, a quantity of diluted aqua ammonia.
WATER
The water used in all plating opera¬tions, both in mixing the various chemicals, and in making the plating solutions, should either be distilled or well filtered rain water ; spring and well water invariably containing various impu¬rities, very detrimental to the working of the solutions. It should form no cloud upon the addition of a few drops of nitrate of silver.
WHAT İS THE FULMINATE OF GOLD?
FULMINATE OF GOLD
This salt is a dark, brown powder, and veiy highly explosive. It is formed by the addition of ammonia, or a solu¬tion of any salt of ammonia to a solution of chloride of gold. It is sometimes used in form¬ing electro-gilding solutions, but owing to its dangerous properties, the inexperienced operator should never undertake its manufacture.
This salt is a dark, brown powder, and veiy highly explosive. It is formed by the addition of ammonia, or a solu¬tion of any salt of ammonia to a solution of chloride of gold. It is sometimes used in form¬ing electro-gilding solutions, but owing to its dangerous properties, the inexperienced operator should never undertake its manufacture.
YÜZEY GERİLİMİNİN KONTROLÜ NASIL YAPILIR?
Islatıcılar veya yüzey aktif kimyasallardan 4. Ders’ te kısaca bahsedilmiş ve metal yüzeylerinin temizlenmesindeki rolü ele alınmıştı. Hafızanızı biraz tazeleyelim: Islatıcı yüzey aktif bir maddedir. Islatıcının molekülleri yüzeyleri veya arayüzeyleri tercih eder. Temizleme işlemlerinde doğrudan yağ damlası ile metal yüzeyin arasına girerler. Yağ damlasını yavaş yavaş sökerler çünkü metal yüzey ile aralarındaki çekim kuvveti, yağ damlası ile metal yüzey arasındaki çekim kuvvetinden daha fazladır. Yağ ile metal arasındaki çekim kuvveti (Van der Waals) yeteri derecede zayıflatıldığında metal yüzeyindeki yağ sökecektir.
Yüzey aktif kimyasallar ile kaplama banyoları arasında önemli bir ilişki vardır. Örneğin bir nikel kaplama banyosunda anti-pit kimyasalı yaygın olarak kullanılır. Anti-pit kimyasalı da ıslatıcı ile aynı şekilde iş görür. Kir parçalarının ve katoda yapışmış hidrojen kabarcıklarının altına ilerler ve kaplama yüzeyinde çukurluklar oluşmasına neden olmadan önce sökülmesini sağlar. Eğer kir parçasının veya kabarcığın etrafı kaplanmaya devam eder ve bir süre sonra kir parçası veya hava kabarcığı sökülürse geride bir boşluk bırakır. Buna çukur (pit) denir.
Yüzey aktif kimyasallar ile kaplama banyolarındaki kirlenme sorunu arasında da önemli bir ilişki vardır. Kaplama banyolarına az miktarda katıldıklarında, banyodan çıkarılan malzemenin üzerinde kalan kaplama çözeltisinin akıcılığını artırarak banyoya daha çabuk düşmesini sağladığından banyonun eksilmesini azaltırlar. Krom kaplama banyosunda da önemlidirler çünkü, banyo yüzeyinde hava kabarcıklarından bir katman oluşturarak kromik asidin havaya karışmasını en aza indirirler. Bu hususlara ileride yeri geldikçe değinilecektir.
Islatıcıların kimyasal analizlerde kontrol edilebilmesini sağlayan bazı molekül türleri mevcut olmakla beraber, bu oldukça zor bir girişimdir. Çünkü kullanılan miktar çok küçüktür. Bundan dolayı kaplama işlemlerinde kullanılan çoğu ıslatıcı kimyasal yöntemler yerine fiziksel yöntemlerle kontrol edilir. Fiziksel yöntem yüzey geriliminin ölçülmesi prensibine dayanır.
Yüzey gerilimi 1. Ders’ te yüzey enerjisi işlenirken ele alınmıştı. Bununla ilgili olarak yağlı bir yüzeye damlayan bir damla suyun kendiliğinden top şeklini alması (Şekil 19), aynı damlanın temiz bir yüzeye damladığında ise bir film tabakası şeklinde yayıldığı örnek verilmişti. Bu davranışın nedeni olarak, bir sıvının yüzeyindeki moleküllerinin içerideki moleküllerden daha az sayıda komşu moleküle sahip olması söylenmişti. Bu yüzey enerjisini artırır. Bildiğiniz üzere enerji uzaktan etki eden bir kuvvet olarak tanımlanabilir. Yüzey enerjisi durumunda ise, yüzeyde etkili olan kuvvete yüzey gerilimi denir.
Yüzey gerilimi, birim uzunluktaki yüzeye etki eden bir kuvvettir.
Islatıcı banyonun yüzey gerilimini değiştirecek şekilde etki eder, düşürür. Bu düşmenin miktarı banyoda bulunan ıslatıcı miktarına bağlıdır. Yüzey gerilimini ölçerek kaplama banyosunda ne kadar ıslatıcı olduğunu tespit edebilirsiniz.
Yüzey gerilimini ölçmenin değişik yolları vardır. Bunlardan en yaygın kullanılanlar
1. de Nouy tansiyometresi
2. Damla stalagmometresidir.59
Tansiyometre yöntemi daha bilimsel olup daha hassas kontrol istendiğinde tercih edilir. Ayrıca stalagmometre ile ölçülemeyen, iki sıvı arasındaki arayüzey geriliminin ölçümünde de kullanılır. Stalagmometrenin fiyatı daha ucuz olup kullanımı da basittir. Bu nedenle çoğu kaplama tesisinde bu alet bulunur.
Tansiyometre sıvı yüzeyinden temiz bir platin halkayı çekmek için gerekli olan kuvveti ölçer. Stalagmometre ise kalibre edilmiş bir pipetten (Şekil 19) damlayan damıtılmış saf su damla sayısını aynı hacimdeki kaplama çözeltisi damla sayısı ile karşılaştırır. Yüzey gerilimi azaldıkça oluşan damla sayısı artar. Stalagmometrenin kullanımı şu şekildedir:
1. 20 °C’ de pipetin iki çizgisi arasında damlayan damla sayısı sayılır. Bulunan sayı stalagmometre sabitidir.
2. Şimdi cihaz 20 °C sıcaklıktaki test edilecek kaplama çözeltisi ile doldurulur ve damlalar sayılır.
3. Kaplama çözeltisinin özgül ağırlığı bir hidrometre veya piknometre ile ölçülür.
Kaplama çözeltisinin yüzey gerilimi aşağıdaki formülle hesaplanır:
72,7 saf suyun 20 °C’ deki yüzey gerilim değeridir. Yüzey uzunluğunun cm.si başına düşen dyn (metrik sistemde bir kuvvet birimi) sayısını ifade eder. Eğer kuvvet ve uzunluk olarak İngiliz ölçü sistemini kullanmak istersek 0,005 pound/foot değerini kullanmalıyız.
Nouy tansiyometresinde standart bir temiz platin halkayı 20 °C’ deki saf sudan çıkarmak için gerekli çekim kuvveti ile, 20 °C’ deki kaplama çözeltisinden çıkarmak için gerekli çekim kuvveti karşılaştırılır. Kuvveti ölçmek için burulmalı terazi kullanılır. Yüzey gerilimini tanımlamak için kullanılan formül şu şekildedir:
Çoğu kaplamacı hesaplama yapmaktansa, kolay yoldan, kaplama çözeltisi en uygun şekilde hazırlanmışken stalagmometrede saydıkları damla sayısı ile kontrol esnasında saydıkları damla sayısını karşılaştırırlar. En uygun çalışma değerine dönmek için ne zaman ve ne kadar yüzey aktif ilave etmeniz gerektiğini hazırlayacağınız küçük bir çizelge veya tablodan takip edebilirsiniz.
Yüzey gerilimi testine başlamadan önce kaplama çözeltisinin filtre edilmiş ve içindeki kir parçacıklarının giderilmiş olduğundan emin olmalısınız. Yüzey geriliminin sıcaklık değişimlerine karşı hassas olduğunu ve hızla değiştiğini aklınızdan çıkarmayın ve yüzey gerilim testini her zaman aynı sıcaklıkta yapın.
Artık kaplama banyosu bileşiminin kontrolü konusuna geçebiliriz.
Yüzey aktif kimyasallar ile kaplama banyoları arasında önemli bir ilişki vardır. Örneğin bir nikel kaplama banyosunda anti-pit kimyasalı yaygın olarak kullanılır. Anti-pit kimyasalı da ıslatıcı ile aynı şekilde iş görür. Kir parçalarının ve katoda yapışmış hidrojen kabarcıklarının altına ilerler ve kaplama yüzeyinde çukurluklar oluşmasına neden olmadan önce sökülmesini sağlar. Eğer kir parçasının veya kabarcığın etrafı kaplanmaya devam eder ve bir süre sonra kir parçası veya hava kabarcığı sökülürse geride bir boşluk bırakır. Buna çukur (pit) denir.
Yüzey aktif kimyasallar ile kaplama banyolarındaki kirlenme sorunu arasında da önemli bir ilişki vardır. Kaplama banyolarına az miktarda katıldıklarında, banyodan çıkarılan malzemenin üzerinde kalan kaplama çözeltisinin akıcılığını artırarak banyoya daha çabuk düşmesini sağladığından banyonun eksilmesini azaltırlar. Krom kaplama banyosunda da önemlidirler çünkü, banyo yüzeyinde hava kabarcıklarından bir katman oluşturarak kromik asidin havaya karışmasını en aza indirirler. Bu hususlara ileride yeri geldikçe değinilecektir.
Islatıcıların kimyasal analizlerde kontrol edilebilmesini sağlayan bazı molekül türleri mevcut olmakla beraber, bu oldukça zor bir girişimdir. Çünkü kullanılan miktar çok küçüktür. Bundan dolayı kaplama işlemlerinde kullanılan çoğu ıslatıcı kimyasal yöntemler yerine fiziksel yöntemlerle kontrol edilir. Fiziksel yöntem yüzey geriliminin ölçülmesi prensibine dayanır.
Yüzey gerilimi 1. Ders’ te yüzey enerjisi işlenirken ele alınmıştı. Bununla ilgili olarak yağlı bir yüzeye damlayan bir damla suyun kendiliğinden top şeklini alması (Şekil 19), aynı damlanın temiz bir yüzeye damladığında ise bir film tabakası şeklinde yayıldığı örnek verilmişti. Bu davranışın nedeni olarak, bir sıvının yüzeyindeki moleküllerinin içerideki moleküllerden daha az sayıda komşu moleküle sahip olması söylenmişti. Bu yüzey enerjisini artırır. Bildiğiniz üzere enerji uzaktan etki eden bir kuvvet olarak tanımlanabilir. Yüzey enerjisi durumunda ise, yüzeyde etkili olan kuvvete yüzey gerilimi denir.
Yüzey gerilimi, birim uzunluktaki yüzeye etki eden bir kuvvettir.
Islatıcı banyonun yüzey gerilimini değiştirecek şekilde etki eder, düşürür. Bu düşmenin miktarı banyoda bulunan ıslatıcı miktarına bağlıdır. Yüzey gerilimini ölçerek kaplama banyosunda ne kadar ıslatıcı olduğunu tespit edebilirsiniz.
Yüzey gerilimini ölçmenin değişik yolları vardır. Bunlardan en yaygın kullanılanlar
1. de Nouy tansiyometresi
2. Damla stalagmometresidir.59
Tansiyometre yöntemi daha bilimsel olup daha hassas kontrol istendiğinde tercih edilir. Ayrıca stalagmometre ile ölçülemeyen, iki sıvı arasındaki arayüzey geriliminin ölçümünde de kullanılır. Stalagmometrenin fiyatı daha ucuz olup kullanımı da basittir. Bu nedenle çoğu kaplama tesisinde bu alet bulunur.
Tansiyometre sıvı yüzeyinden temiz bir platin halkayı çekmek için gerekli olan kuvveti ölçer. Stalagmometre ise kalibre edilmiş bir pipetten (Şekil 19) damlayan damıtılmış saf su damla sayısını aynı hacimdeki kaplama çözeltisi damla sayısı ile karşılaştırır. Yüzey gerilimi azaldıkça oluşan damla sayısı artar. Stalagmometrenin kullanımı şu şekildedir:
1. 20 °C’ de pipetin iki çizgisi arasında damlayan damla sayısı sayılır. Bulunan sayı stalagmometre sabitidir.
2. Şimdi cihaz 20 °C sıcaklıktaki test edilecek kaplama çözeltisi ile doldurulur ve damlalar sayılır.
3. Kaplama çözeltisinin özgül ağırlığı bir hidrometre veya piknometre ile ölçülür.
Kaplama çözeltisinin yüzey gerilimi aşağıdaki formülle hesaplanır:
72,7 saf suyun 20 °C’ deki yüzey gerilim değeridir. Yüzey uzunluğunun cm.si başına düşen dyn (metrik sistemde bir kuvvet birimi) sayısını ifade eder. Eğer kuvvet ve uzunluk olarak İngiliz ölçü sistemini kullanmak istersek 0,005 pound/foot değerini kullanmalıyız.
Nouy tansiyometresinde standart bir temiz platin halkayı 20 °C’ deki saf sudan çıkarmak için gerekli çekim kuvveti ile, 20 °C’ deki kaplama çözeltisinden çıkarmak için gerekli çekim kuvveti karşılaştırılır. Kuvveti ölçmek için burulmalı terazi kullanılır. Yüzey gerilimini tanımlamak için kullanılan formül şu şekildedir:
Çoğu kaplamacı hesaplama yapmaktansa, kolay yoldan, kaplama çözeltisi en uygun şekilde hazırlanmışken stalagmometrede saydıkları damla sayısı ile kontrol esnasında saydıkları damla sayısını karşılaştırırlar. En uygun çalışma değerine dönmek için ne zaman ve ne kadar yüzey aktif ilave etmeniz gerektiğini hazırlayacağınız küçük bir çizelge veya tablodan takip edebilirsiniz.
Yüzey gerilimi testine başlamadan önce kaplama çözeltisinin filtre edilmiş ve içindeki kir parçacıklarının giderilmiş olduğundan emin olmalısınız. Yüzey geriliminin sıcaklık değişimlerine karşı hassas olduğunu ve hızla değiştiğini aklınızdan çıkarmayın ve yüzey gerilim testini her zaman aynı sıcaklıkta yapın.
Artık kaplama banyosu bileşiminin kontrolü konusuna geçebiliriz.
RECOVERING SILVER FROM OLD SILVER PLATING SOLUTIONS, HOW TO MAKE RECOVERING SILVER FROM OLD SILVER PLATING SOLUTIONS?
Add muriatic acid to the plating solution until it is strongly acid. This will cause the liberation of a large quantity of hydrocyanic acid gas, which, as we have stated before, is very poisonous, and should, under no circumstances, be inhaled. It also causes a precipitate of silver, in the form of chloride of silver, which should be a very light or pure white color, but is more often tinted with red, owing to the copper nearly always present in old solutions, being precipitated with the silver. The 1 he copper can be removed, if desired, after the precipitate has been washed by treating it with warm muriatic acid. This dissolves the copper and leaves the chloride of silver unchanged, which may be converted into metallic silver, by the process described on page 88, or, it may be used in forming a new plating solution.
In making nitrate of silver the liquid first poured off, as well as all the wash waters should be preserved, mixed together, and a strong solution of common salt or dilute muriatic acid added to them until it ceases to produce a precipitate.
This precipitate is the chloride of silver, which should be well washed, and may then be converted into metallic silver, or placed in a well stoppered bottle, and laid away for future use, as occasion may require, but it must be care fully protected from the light, which decomposes it rapidly.
The recovery of metal from the stripping liquids, may be accomplished by evaporating them down to a very small bulk, which will crystalize upon cooling. The residue is then dissolved in water, and the metal precipitated by means of strong solution of common salt, or by dilute muriatic acid.
The precipitate thus lormed will likely contain a small amount of copper, which is dissolved by warm muriatic acid, and leaves the pure chloride of silver.
In making nitrate of silver the liquid first poured off, as well as all the wash waters should be preserved, mixed together, and a strong solution of common salt or dilute muriatic acid added to them until it ceases to produce a precipitate.
This precipitate is the chloride of silver, which should be well washed, and may then be converted into metallic silver, or placed in a well stoppered bottle, and laid away for future use, as occasion may require, but it must be care fully protected from the light, which decomposes it rapidly.
The recovery of metal from the stripping liquids, may be accomplished by evaporating them down to a very small bulk, which will crystalize upon cooling. The residue is then dissolved in water, and the metal precipitated by means of strong solution of common salt, or by dilute muriatic acid.
The precipitate thus lormed will likely contain a small amount of copper, which is dissolved by warm muriatic acid, and leaves the pure chloride of silver.
PRACTICAL OPERATION OF GILDING SOLUTIONS
All solutions for gold plating should be used at a temperature of about 1500 Fahr., and when not in use should be carefully covered over to protect it from the dust and other impurities. The amount of gold held in the solution may vary greatly without materially affecting it working, provided always, that it also contains a proportionate amount of cyanide of potassium. The proportions of gold and cyanide of potassium in the solution may vary within certain limits, generally from twenty-five to fifty per cent, more than is required to simply dissolve the cyanide of gold (see page 49) without impairing its usefulness.
Too much cyanide of potassium causes the deposit to have a dirty discolored appearance. After the solution has been in use for some time it often works badly in consequence of the proportions of gold and cyanide becoming dis¬arranged. This is caused sometimes by using anodes with greater or less surface than the articles to be plated.
When the anode presents a larger surface in the solution than the articles to be plated, the solution rapidly becomes richer in gold, which uniting with the free cyanide, soon uses it all up in forming the double cyanide of gold and potassium, leaving but very little or none at all to form the "free cyanide" so essential to its perfect working.
This condition is indicated by the anode becoming covered with crust or sediment, and is remedied by using an anode with smaller surface than the articles to be plated, or a sufficient amount of a solution of cyanide of potassium may be added.
When the anode becomes black, and has a slimy appearance, the solution needs more gold, which may be supplied by using an anode of greater surface until the solution is again properly proportioned, which will be indicated by the anode remaining bright and clean and giving a good deposit. By carefully observing these indications, and applying the proper remedy, the solution may be kept in order
almost indefinitely, but after very long continued use it becomes contaminated with various impurities, some of them accidentally introduced, and others set free by the dissolving of the anode.
Gold anodes invariably contain traces of silver, which is dissolved in the solution, and by being deposited with the gold increases its paleness of color. When from any of these reasons the solution ceases to work satisfactorily, all the metal held in solution may be recovered separately, and used to start out anew,
Too much cyanide of potassium causes the deposit to have a dirty discolored appearance. After the solution has been in use for some time it often works badly in consequence of the proportions of gold and cyanide becoming dis¬arranged. This is caused sometimes by using anodes with greater or less surface than the articles to be plated.
When the anode presents a larger surface in the solution than the articles to be plated, the solution rapidly becomes richer in gold, which uniting with the free cyanide, soon uses it all up in forming the double cyanide of gold and potassium, leaving but very little or none at all to form the "free cyanide" so essential to its perfect working.
This condition is indicated by the anode becoming covered with crust or sediment, and is remedied by using an anode with smaller surface than the articles to be plated, or a sufficient amount of a solution of cyanide of potassium may be added.
When the anode becomes black, and has a slimy appearance, the solution needs more gold, which may be supplied by using an anode of greater surface until the solution is again properly proportioned, which will be indicated by the anode remaining bright and clean and giving a good deposit. By carefully observing these indications, and applying the proper remedy, the solution may be kept in order
almost indefinitely, but after very long continued use it becomes contaminated with various impurities, some of them accidentally introduced, and others set free by the dissolving of the anode.
Gold anodes invariably contain traces of silver, which is dissolved in the solution, and by being deposited with the gold increases its paleness of color. When from any of these reasons the solution ceases to work satisfactorily, all the metal held in solution may be recovered separately, and used to start out anew,
HOW TO MAKE A BATTERY?
One of the best batteries for electro-plating purposes is the ordinary gravity battery, of which there are various styles, all of them, however, being made on the same general plan.
To construct a battery of this kind, procure two or three pieces of sheet copper five or six inches long, and about two inches wide and fasten them together by means of a copper rivet through the center; to the end of one of the strips fasten a copper wire about a foot long by means of another copper rivet. The wire must be well insulated except at its two extremities, in order to prevent its being corroded at the surface of the solution.
India rubber is the best substance for this purpose and is generally used in batteries of this description, but where wire already coated with rubber cannot be procured, a very good substitute may be obtained by wrapping the wire carefully with tarred twine and giving it a final coating of melted beeswax, containing a very little lard.
The zinc electrode is more difficult to make, and where it is convenient it will be more economical to buy them. They are made in a number of shapes, the object being to obtain an electrode exposing the largest amount of surface to the action of the solution for a given weight of metal, and a the same time to be of such a shape as to allow the bubbles of hydrogen gas formed by the action of the battery to escape freely.
A very convenient form is that of a wheel with six spokes, the "hub" projecting upward about two or two and a half inches with the connecting wire cast in the center of it. This wire should be from from from four to six inches in length.
Zincs of this kind are suspended in the solution by passing the wire through a hole in a small flat piece of wood long enough to reach across the vessel, and is fastened to it at the proper height by means ol a small clamp of any kind, or by simply taking a turn of the connecting wire around the supporting stick. A very good clamp for securing the zincs in position may be made by drilling a hole large enough to admit the wire, throug a small piece or block of metal, and then drilling another hole at right angles, and intercepting the first one, and fit-ting it with a screw, and is used by slipping it over the connecting wire until it rests on the wooden support, and fastening it to the wire by (means of the screw.
Zincs are often cast in the form of a thick ring with a hook shaped projection of the same metal extending upwards about three inches and at right angles with the ring. This zinc is used by attaching it to the jar by simply hook ing it over the edge. The top of the "hook" has two holes drilled in it, intercepting each other, one of them being fitted with a set screw for clamping the connecting wire.
There are several other forms of zincs, but these two we have described embody the main features of all the others and of these two we think the first is the best on account of the larger amount of surface exposed and the more economical distribution of the metal.
The dimensions of a well proportioned zinc should be from five to six inches wide, one inch to one inch and a half high, and the spokes and rim about three-eighths to half an inch thick.
The jar for containing the battery should be about ten inches high and from six to seven inches wide, with straight sides and flat bottom, and may be of either glass or earthen ware.
To set the battery in operation, fill the jar with water to within two inches of the top and add one pound of sulphate of zinc. When it is all dissolved take the copper electrode and bend the strips outward until their ends are all about equally distant, and place it in the bottom of the jar ; then add a small handfull of sulphate of copper and suspend the zinc in the solution, about two inches above the copper, and in a short time the battery will be ready for use. When using more than one jar or cell of bat¬tery at one time they should be connected together by attaching the zinc of one jar to the copper of the next, the zinc of the second to the copper of the third, and so on, leaving the copper of the first and the zinc of the last jar for connecting with the wires leading from the plating solution.
When not in use the terminal wires should be connected together in order that the battery may continue to work, otherwise the blue solution will gradually raise, and in a few days time surround the zinc and soon destroy it. When the blue solution has almost disappeared add a few crystals of sulphate of copper. After being in use for some time the solution becomes saturated with sulphate of zinc, which will creep up the sides and over the top of the vessel and greatly impair its working. When this is ob¬served draw off about a pint from the top of the solution, and replace it with water, taking care not to stir the solution.
This form of battery is termed the "gravity battery" because the two solutions which are employed in it, sulphate of zinc and sulphate of copper, are separated, but allowed to touch each other by taking advantage of the difference in their weights, the sulphate of copper solution being the heaviest, remaining at the bottom sur rounding the copper electrode, and the sulphate of zinc, being the lightest, remains at the top and surrounds the sine.
After this battery has been in use five or six months the zincs will require renewing, the copper in the meantime having greatly in¬creased in size, the copper of the sulphate of copper havin been deposited upon it, while the liberated sulphuric acid attacked the zinc, forming sulphate of zinc. When the deposit upon the copper has become about a quarter of an inch thick, it should be removed by bending the strip until the deposit cracks. It may then be easily removed by inserting a chisel between it and the original copper strip. Quite a quantity of perfectly pure copper may be collected in this manner, which is valuable, and should be preserved.
The zincs should be taken out at least once a month, and thorougly scraped and cleaned.
This battery is preferred for electro-plating operations on account of the steady, uniform carrent it produces, which is a very important consideration in obtaining a good deposit.
The strength of the current may be varied by raising or lowering the zinc in the solution. When a weak current is desired the zinc should be raised so that but a very small portion of it is immersed in the solution, the greatest strength being obtained when all the zincs are wholly immersed.
This battery possesses a very great advantage over all others, from the fact that it always generates a current of uniform strength during long continued action, which is something that other batteries, although generating a more powerful current, often fail to do. It is also much more easily managed, and requires less care and attention to keep it in good working order, and, in fact, the only objection that can be legitimately raised against it is, that it deteriorates rapidly when not in active service, the blue vitrol solution, raising slowly, but surely, and finally surrounding the zinc, which is quickly corroded and rendered unfit for use until it has been thoroughly cleaned. When there is but little work to do, and the battery forced to remain idle the greater part of the time, the old style "Daniel" battery will probably give the best results. It consists of a strip of copper five or six inches wide and fifteen or eighteen inches long, rolled in the form of a cylinder that will fit the inside of the battery jar loosely. Inside of this copper cylinder is placed an earthenware cup which, in the abesnce of regular porous cups, made especially for this style of battery, may consist of a small unglazed flower pot, the hole in the bottom being securely stopped up. Inside of this porous cup is placed a bar, or better still, a small cylinder of zinc.
To put the battery in operation, fill the outer jar with a solution of blue vitrol, and the porous cup containing the zinc, with a tolerably strong solution of sulphate of zinc, or a mixture of ten or twelve parts of water, to which one part of sulphuric acid is added slowly, may be used instead. The blue vitrol solution must be kept strong, and completely saturated, by carefully observing that there is at all times a few crystals of blue vitrol in the solution, and by adding a small handfull, from time to time, as fast as it is dissolved. The zinc should be supported in some way, and not allowed to touch the sides, or bottom of the porous cup. This is usually accomplished by laying a small stick across the porous cup, and suspending the zinc from it by the connecting wire.
This battery generates a steady and uniform cnrrent, but of less strength than that generated by the "Gravity" battery. When the battery is to remain idle any considerable length of time, the zincs and coppers should be taken out, washed and laid away, and the porous cups removed and the liquid they contain poured
Into a bottle and preserved for future use. The fclue vitrol solution may remain in the larger fcutside jar, which should be carefully covered i)ver to keep out the dust.
To construct a battery of this kind, procure two or three pieces of sheet copper five or six inches long, and about two inches wide and fasten them together by means of a copper rivet through the center; to the end of one of the strips fasten a copper wire about a foot long by means of another copper rivet. The wire must be well insulated except at its two extremities, in order to prevent its being corroded at the surface of the solution.
India rubber is the best substance for this purpose and is generally used in batteries of this description, but where wire already coated with rubber cannot be procured, a very good substitute may be obtained by wrapping the wire carefully with tarred twine and giving it a final coating of melted beeswax, containing a very little lard.
The zinc electrode is more difficult to make, and where it is convenient it will be more economical to buy them. They are made in a number of shapes, the object being to obtain an electrode exposing the largest amount of surface to the action of the solution for a given weight of metal, and a the same time to be of such a shape as to allow the bubbles of hydrogen gas formed by the action of the battery to escape freely.
A very convenient form is that of a wheel with six spokes, the "hub" projecting upward about two or two and a half inches with the connecting wire cast in the center of it. This wire should be from from from four to six inches in length.
Zincs of this kind are suspended in the solution by passing the wire through a hole in a small flat piece of wood long enough to reach across the vessel, and is fastened to it at the proper height by means ol a small clamp of any kind, or by simply taking a turn of the connecting wire around the supporting stick. A very good clamp for securing the zincs in position may be made by drilling a hole large enough to admit the wire, throug a small piece or block of metal, and then drilling another hole at right angles, and intercepting the first one, and fit-ting it with a screw, and is used by slipping it over the connecting wire until it rests on the wooden support, and fastening it to the wire by (means of the screw.
Zincs are often cast in the form of a thick ring with a hook shaped projection of the same metal extending upwards about three inches and at right angles with the ring. This zinc is used by attaching it to the jar by simply hook ing it over the edge. The top of the "hook" has two holes drilled in it, intercepting each other, one of them being fitted with a set screw for clamping the connecting wire.
There are several other forms of zincs, but these two we have described embody the main features of all the others and of these two we think the first is the best on account of the larger amount of surface exposed and the more economical distribution of the metal.
The dimensions of a well proportioned zinc should be from five to six inches wide, one inch to one inch and a half high, and the spokes and rim about three-eighths to half an inch thick.
The jar for containing the battery should be about ten inches high and from six to seven inches wide, with straight sides and flat bottom, and may be of either glass or earthen ware.
To set the battery in operation, fill the jar with water to within two inches of the top and add one pound of sulphate of zinc. When it is all dissolved take the copper electrode and bend the strips outward until their ends are all about equally distant, and place it in the bottom of the jar ; then add a small handfull of sulphate of copper and suspend the zinc in the solution, about two inches above the copper, and in a short time the battery will be ready for use. When using more than one jar or cell of bat¬tery at one time they should be connected together by attaching the zinc of one jar to the copper of the next, the zinc of the second to the copper of the third, and so on, leaving the copper of the first and the zinc of the last jar for connecting with the wires leading from the plating solution.
When not in use the terminal wires should be connected together in order that the battery may continue to work, otherwise the blue solution will gradually raise, and in a few days time surround the zinc and soon destroy it. When the blue solution has almost disappeared add a few crystals of sulphate of copper. After being in use for some time the solution becomes saturated with sulphate of zinc, which will creep up the sides and over the top of the vessel and greatly impair its working. When this is ob¬served draw off about a pint from the top of the solution, and replace it with water, taking care not to stir the solution.
This form of battery is termed the "gravity battery" because the two solutions which are employed in it, sulphate of zinc and sulphate of copper, are separated, but allowed to touch each other by taking advantage of the difference in their weights, the sulphate of copper solution being the heaviest, remaining at the bottom sur rounding the copper electrode, and the sulphate of zinc, being the lightest, remains at the top and surrounds the sine.
After this battery has been in use five or six months the zincs will require renewing, the copper in the meantime having greatly in¬creased in size, the copper of the sulphate of copper havin been deposited upon it, while the liberated sulphuric acid attacked the zinc, forming sulphate of zinc. When the deposit upon the copper has become about a quarter of an inch thick, it should be removed by bending the strip until the deposit cracks. It may then be easily removed by inserting a chisel between it and the original copper strip. Quite a quantity of perfectly pure copper may be collected in this manner, which is valuable, and should be preserved.
The zincs should be taken out at least once a month, and thorougly scraped and cleaned.
This battery is preferred for electro-plating operations on account of the steady, uniform carrent it produces, which is a very important consideration in obtaining a good deposit.
The strength of the current may be varied by raising or lowering the zinc in the solution. When a weak current is desired the zinc should be raised so that but a very small portion of it is immersed in the solution, the greatest strength being obtained when all the zincs are wholly immersed.
This battery possesses a very great advantage over all others, from the fact that it always generates a current of uniform strength during long continued action, which is something that other batteries, although generating a more powerful current, often fail to do. It is also much more easily managed, and requires less care and attention to keep it in good working order, and, in fact, the only objection that can be legitimately raised against it is, that it deteriorates rapidly when not in active service, the blue vitrol solution, raising slowly, but surely, and finally surrounding the zinc, which is quickly corroded and rendered unfit for use until it has been thoroughly cleaned. When there is but little work to do, and the battery forced to remain idle the greater part of the time, the old style "Daniel" battery will probably give the best results. It consists of a strip of copper five or six inches wide and fifteen or eighteen inches long, rolled in the form of a cylinder that will fit the inside of the battery jar loosely. Inside of this copper cylinder is placed an earthenware cup which, in the abesnce of regular porous cups, made especially for this style of battery, may consist of a small unglazed flower pot, the hole in the bottom being securely stopped up. Inside of this porous cup is placed a bar, or better still, a small cylinder of zinc.
To put the battery in operation, fill the outer jar with a solution of blue vitrol, and the porous cup containing the zinc, with a tolerably strong solution of sulphate of zinc, or a mixture of ten or twelve parts of water, to which one part of sulphuric acid is added slowly, may be used instead. The blue vitrol solution must be kept strong, and completely saturated, by carefully observing that there is at all times a few crystals of blue vitrol in the solution, and by adding a small handfull, from time to time, as fast as it is dissolved. The zinc should be supported in some way, and not allowed to touch the sides, or bottom of the porous cup. This is usually accomplished by laying a small stick across the porous cup, and suspending the zinc from it by the connecting wire.
This battery generates a steady and uniform cnrrent, but of less strength than that generated by the "Gravity" battery. When the battery is to remain idle any considerable length of time, the zincs and coppers should be taken out, washed and laid away, and the porous cups removed and the liquid they contain poured
Into a bottle and preserved for future use. The fclue vitrol solution may remain in the larger fcutside jar, which should be carefully covered i)ver to keep out the dust.
DEPOSITING DIFFERENT SHADES OF GOLD.
The color of the deposit may be regulated in quite a number of ways, pure gold having too light a color to be admired by many. An old solution, in which a great many copper articles have been plated, is capable of yielding different colored deposits by means of regulating the size of the anodes, temperature of the solution, the strength of the battery, and, in a degree, the strength of the solution also.
An old solution, that yields a pale yellow deposit, when but a small portion of the anode touches the solution, will yield a darker deposit when the anode is further immersed, and finally, when it is entirely immersed, the deposit will be of a red color.
The temperature of the solution effects the color of the deposit, it being much darker and richer when the solution is used hot than when it is used cold, and it is claimed by a great many electro-platers, and justly too, that a
metal deposited from a warm solution is harder, and consequently more durable, than a metal deposited from a cold solution.
The strength of the battery also has a great deal to do with the color of the deposit, a moderately weak current producing a much lighter colored deposit than that produced by a much stronger battery. There are, however, certain limits regulating both the temperature and battery power, beyond which it is not safe to venture. The temperature should never be allowed to greatly exceed i6o° Fahr.
The amount of battery power is a more difficult matter to determine, as it varies with the amount of surface presented by the articles to be plated. Generally speaking, three cups of the ordinary Callaud or gravity battery will be amply sufficient for operations on the larger scale, while one, or, perhaps, two cups will answer for the gilding of small articles, or electro-plating on a small scale.
Gold deposited by the electric current is not always pure gold, as other metals are often deposited with it in order to produce the desired color or tint, and in large electro plating establishments, or where a great variety of work is done, a number of gilding solutions are used, each of them yielding a different colored deposit. However, one solution is capable of yielding, with careful and judicious management, a deposit of gold varying in color from the light yellow of almost pure gold, to a deposit so alloyed with copper as to resemble 14 karat gold, and which it really is.
In order to accomplish this, the solution must contain a small amount of copper. This metal is always present in old gilding solutions, caused by a very minute portion of the metal being dis¬solved from each article of copper that has been plated in the solution. Of course the amount of metal dissolved from each individual article is very small indeed, but when in the course of time a great many of them have been plated, the aggregate of the dissolved copper is con¬siderable, and quite sufficient to change the color of the deposit. A freshly made solution used quite hot, with a large gold anode and a toler¬ably strong battery, will generally give a satis¬factory deposit, but should it still be of too light a color, remove the gold anode and substitute in its place a clean one of copper and work the solution with it until the deposit begins to slightly change its color, and then replace it with the gold anode. If the copper anode has been weighed before, and again just after using it, as above mentioned, it will be discovered that a portion of it has been dissolved in the solution, which by being deposited with the gold gives it a richer and darker color.
To obtain a green colored deposit, add a small quantity of the ordinary silver plating solution to the gilding solution, with gentle stirring, taking care to add just enough to produce the desired effect, as where too much of the silver solution is added it is liable to spoil it.
White gilding is produced by adding a solution of nitrate of silver to the gilding solution, until the desired colored deposit is obtained, which must be ascertained by actual trial.
Pink gold is obtained by first plating the articles in a cold and weak solution, with a weak battery, then giving them another coat in a hot and strong solution that has considerable copper in it, using a more powerful battery in order to obtain a dark colored deposit, then give them an exceedingly thin coating in the ordinary silver plating solution, and finally burnish them. The coating of silver should be barely sufficient to
5 impart a lighter tinge to the deposit which, if the operation has been successful, will be of a beautiful pink color when burnished.
To gild the inside surface of articles, such as cups, cream pitchers, and similar articles, fill them with the solution, and suspend a gold anode in them, and attach the article itself to the wire leading from the zinc pole of the battery. The lips of the pitcher, and other portions that the solution does not touch, may be plated by laying a rag wetted with the gilding solution upon the part, leaving a portion of it immersed in the solution contained in the vessel. The outside surface of the article, or that portion of it you may not want to gold plate, may be coated with a solution of sealing wax dissolved in naptha, or simply painted over with melted beeswax, and the articles placed in the gilding solution in the ordinary way, and after the gilding operation has been completed, the wax is easily removed.
An old solution, that yields a pale yellow deposit, when but a small portion of the anode touches the solution, will yield a darker deposit when the anode is further immersed, and finally, when it is entirely immersed, the deposit will be of a red color.
The temperature of the solution effects the color of the deposit, it being much darker and richer when the solution is used hot than when it is used cold, and it is claimed by a great many electro-platers, and justly too, that a
metal deposited from a warm solution is harder, and consequently more durable, than a metal deposited from a cold solution.
The strength of the battery also has a great deal to do with the color of the deposit, a moderately weak current producing a much lighter colored deposit than that produced by a much stronger battery. There are, however, certain limits regulating both the temperature and battery power, beyond which it is not safe to venture. The temperature should never be allowed to greatly exceed i6o° Fahr.
The amount of battery power is a more difficult matter to determine, as it varies with the amount of surface presented by the articles to be plated. Generally speaking, three cups of the ordinary Callaud or gravity battery will be amply sufficient for operations on the larger scale, while one, or, perhaps, two cups will answer for the gilding of small articles, or electro-plating on a small scale.
Gold deposited by the electric current is not always pure gold, as other metals are often deposited with it in order to produce the desired color or tint, and in large electro plating establishments, or where a great variety of work is done, a number of gilding solutions are used, each of them yielding a different colored deposit. However, one solution is capable of yielding, with careful and judicious management, a deposit of gold varying in color from the light yellow of almost pure gold, to a deposit so alloyed with copper as to resemble 14 karat gold, and which it really is.
In order to accomplish this, the solution must contain a small amount of copper. This metal is always present in old gilding solutions, caused by a very minute portion of the metal being dis¬solved from each article of copper that has been plated in the solution. Of course the amount of metal dissolved from each individual article is very small indeed, but when in the course of time a great many of them have been plated, the aggregate of the dissolved copper is con¬siderable, and quite sufficient to change the color of the deposit. A freshly made solution used quite hot, with a large gold anode and a toler¬ably strong battery, will generally give a satis¬factory deposit, but should it still be of too light a color, remove the gold anode and substitute in its place a clean one of copper and work the solution with it until the deposit begins to slightly change its color, and then replace it with the gold anode. If the copper anode has been weighed before, and again just after using it, as above mentioned, it will be discovered that a portion of it has been dissolved in the solution, which by being deposited with the gold gives it a richer and darker color.
To obtain a green colored deposit, add a small quantity of the ordinary silver plating solution to the gilding solution, with gentle stirring, taking care to add just enough to produce the desired effect, as where too much of the silver solution is added it is liable to spoil it.
White gilding is produced by adding a solution of nitrate of silver to the gilding solution, until the desired colored deposit is obtained, which must be ascertained by actual trial.
Pink gold is obtained by first plating the articles in a cold and weak solution, with a weak battery, then giving them another coat in a hot and strong solution that has considerable copper in it, using a more powerful battery in order to obtain a dark colored deposit, then give them an exceedingly thin coating in the ordinary silver plating solution, and finally burnish them. The coating of silver should be barely sufficient to
5 impart a lighter tinge to the deposit which, if the operation has been successful, will be of a beautiful pink color when burnished.
To gild the inside surface of articles, such as cups, cream pitchers, and similar articles, fill them with the solution, and suspend a gold anode in them, and attach the article itself to the wire leading from the zinc pole of the battery. The lips of the pitcher, and other portions that the solution does not touch, may be plated by laying a rag wetted with the gilding solution upon the part, leaving a portion of it immersed in the solution contained in the vessel. The outside surface of the article, or that portion of it you may not want to gold plate, may be coated with a solution of sealing wax dissolved in naptha, or simply painted over with melted beeswax, and the articles placed in the gilding solution in the ordinary way, and after the gilding operation has been completed, the wax is easily removed.
GOLD PLATING BY THE BATTERY PROCESS, HOW TO MAKE GOLD PLATING BY THE BATTERY PROCESS?
Solutions for gold plating by means of the electric current may, like those for silver plating be made either by the aid of a battery, or by the chemical process; that made by the chemical process being more quickly made and we think capable of giving better satisfaction to the inexperienced.
The solution made by the battery process has the advantage of being perhaps a trifle more economical, and for this reason is often preferred by the experienced electroplater.
To make the solution by the chemical process, dissolve about one and a half ounces of chloride of gold in water or convert a little over an ounce of gold into chloride and dissolve in water, and add a solution of cyanide of potassium, slowly and at intervals with frequent stirring just as long as it produces a precipitate, but no longer. Great care must be taken to attain the exact neutral paint, that is, when it no longer produces a precipitate upon the addition of a very small quantity of either the cyanide or the chloride of gold solution.
A small quantity of the chloride of gold solution should be reserved and slightly diluted for this purpose, and if it is not all used it may be set away and protected fiom the Iight for future use.
Should the solution contain an excess of either the chloride or the cyanide some of the gold will be held in the clear solution and be poured off, hence the importance of exercising great care in this respect.
When the exact neutral paint has been attained, allow it to settle and pour off the clear liquid, which should be preserved in order to recover any traces of gold it may contain. Then wash the precipitate well by adding water, stirring briskly, and after it has settled, pouring off the clear liquid, repeating the operation a number of times so as.to thoroughly remove all traces of acid.
The wash waters should be preserved as they also are liable to contain traces of gold.
After the last wash water has been poured off pour the precipitate into a paper filter, add a small quantity of water and allow it to drain thoroughly, but not to become dry, as it may possibly contain a small amount of the fulminate of gold which is an extremely dangerous substance, and detonates with terrible violence upon the slightest friction or percussion. When the precipitate has thoroughly drained, collect it in a suitable vessel and add to it a strong solution of cyanide of potassium until barely the whole of it is dissolved, then, having observed the amount of cyanide solution necessary to merely dissolve the precipitate, add about one-fourth as much more to form what is termed by electroplaters "free cyanide" and finally dilute the whole with clean water to one gallon. The amount of gold in the solution may vary greatly from the amount we have given without injury to its working, but in order to obtain the best results it should not contain less than one half an ounce, nor more than ten ounces of gold per gallon. A rather dilute solution gives a somewhat better deposit but is less rapid in its operation than a.stronger one.
To prepare the gilding solution by means of a battery, dissolve two pounds of cyanide of potassium in one gallon of warm water, immerse two sheets of pure gold in this solution and connect them to a moderately strong battery, and allow them to remain in this position and occasionally stirring the liquid, until the proper amount of gold has been dissolved and held in solution. This may be determined by weighing both sheets of gold before placing them in the solution, and then by taking them out of the solution occasionally and weighing them, the amount of gold held in solution may be very easily determined.
Still another and a better means of ascertaining when the solution is ready for use, is to occasionally substitute for a short time a bright and clean sheet of copper, or light colored brass for the gold cathode, until it finally receives a satisfactory deposit. The solution is then ready for work and should be used at a temperature of about I500 Fahr.
The solution made by the battery process has the advantage of being perhaps a trifle more economical, and for this reason is often preferred by the experienced electroplater.
To make the solution by the chemical process, dissolve about one and a half ounces of chloride of gold in water or convert a little over an ounce of gold into chloride and dissolve in water, and add a solution of cyanide of potassium, slowly and at intervals with frequent stirring just as long as it produces a precipitate, but no longer. Great care must be taken to attain the exact neutral paint, that is, when it no longer produces a precipitate upon the addition of a very small quantity of either the cyanide or the chloride of gold solution.
A small quantity of the chloride of gold solution should be reserved and slightly diluted for this purpose, and if it is not all used it may be set away and protected fiom the Iight for future use.
Should the solution contain an excess of either the chloride or the cyanide some of the gold will be held in the clear solution and be poured off, hence the importance of exercising great care in this respect.
When the exact neutral paint has been attained, allow it to settle and pour off the clear liquid, which should be preserved in order to recover any traces of gold it may contain. Then wash the precipitate well by adding water, stirring briskly, and after it has settled, pouring off the clear liquid, repeating the operation a number of times so as.to thoroughly remove all traces of acid.
The wash waters should be preserved as they also are liable to contain traces of gold.
After the last wash water has been poured off pour the precipitate into a paper filter, add a small quantity of water and allow it to drain thoroughly, but not to become dry, as it may possibly contain a small amount of the fulminate of gold which is an extremely dangerous substance, and detonates with terrible violence upon the slightest friction or percussion. When the precipitate has thoroughly drained, collect it in a suitable vessel and add to it a strong solution of cyanide of potassium until barely the whole of it is dissolved, then, having observed the amount of cyanide solution necessary to merely dissolve the precipitate, add about one-fourth as much more to form what is termed by electroplaters "free cyanide" and finally dilute the whole with clean water to one gallon. The amount of gold in the solution may vary greatly from the amount we have given without injury to its working, but in order to obtain the best results it should not contain less than one half an ounce, nor more than ten ounces of gold per gallon. A rather dilute solution gives a somewhat better deposit but is less rapid in its operation than a.stronger one.
To prepare the gilding solution by means of a battery, dissolve two pounds of cyanide of potassium in one gallon of warm water, immerse two sheets of pure gold in this solution and connect them to a moderately strong battery, and allow them to remain in this position and occasionally stirring the liquid, until the proper amount of gold has been dissolved and held in solution. This may be determined by weighing both sheets of gold before placing them in the solution, and then by taking them out of the solution occasionally and weighing them, the amount of gold held in solution may be very easily determined.
Still another and a better means of ascertaining when the solution is ready for use, is to occasionally substitute for a short time a bright and clean sheet of copper, or light colored brass for the gold cathode, until it finally receives a satisfactory deposit. The solution is then ready for work and should be used at a temperature of about I500 Fahr.
GOLD PLATING WITHOUT A BATTERY, HOW TO MAKE GOLD PLATING WITHOUT A BATTERY?
Chloride of gold is the salt generally used in making gilding solutions and in preparing the other salts of gold. The chloride of gold is prepared by dissolving gold in a warm aquaregia which is a mixture composed of one part of nitric acid and two or three of muriatic acid. The gold should be cut up in small pieces and added slowly, care beirtaken not to inhale the gases that arise from the mixture. The gold dissolves very slowly but by gently heating the mixture its action is quickened. Four ounces of this liquid will dissolve about one ounce of gold, and form nearly one and a third ounces of chloride of gold.
When the solution has dissolved all the gold it can, evaporate it with gentle heat to a small bulk which will solidify when cooled. The resultant yellow salt is the chloride of gold which is soluble in water.
Almost all articles of gold contain traces of silver and this metal may now be observed in the solution in the form of chloride of silver, which is a white substance and insoluble in water, which may be removed, if desired, by pouring off the clear liquid, which holas the gold in solution, leaving behind the white chloride of silver, which should be preserved.
Any dark or brownish substance that will not dissolve is very likely metallic gold formed by the chloride being over heated and should be re-converted into chloride.
A solution of gold forms upon the addition of ammonia, a brown precipitate which, when dry, is one of the most powerful and dangerous ex plosives known, and \Wich detonates with the least friction or percussion. One little accident of this kind will put a sudden stop to any further experiments, therefore great care should be taken to prevent its formation, or if formed] to prevent its becoming dry.
The gilding solution is prepared as follows: Dissolve one pennyweight of chloride of gold in a gallon and a half of water; add nine ounces of caustic potash, one ounce of carbon-l ate of potash, and half an ounce of cyanide ofl potash. This solution should be used very hot, but not quite at the boiling point.
The previously cleaned articles of copper or brass are immersed for a short time in this solution, when they should be taken out and dried. Should a thicker coating be desired they should then be dipped in the cyanide of mercury solution (see page 40) and then after rinsing them, be immersed in the gilding solu¬tion again. By repeating this operation several times a very thick deposit may be obtained capable of resisting the action of the strongest acids for a long time.
This process of gold plating is more particularly adapted to the plating of articles not sub¬ject to much handling, as generally only a very thin coating is obtained by it. The work done by this method, however, looks fully as well as that done by the battery process, and to those having no knowledge ot the art of electro metallurgy is somewhat more simple.
The solution also improves with constant usage, acquiring a greenish tint from the presence of copper dissolved from the articles that have been plated in it. This however, does not interfere with its working unless there is a great deal of it held in solution , then it may be deposited with the gold, and impart a darker color to it.
As the solution gradually loses its gold by being deposited, it is necessary to add, from time to time, a small quantity of chloride of gold dissolved in a little water, 4in order to strengthen it, and after three or four such additions it may be necessary to add a small amount of the other salts, always preserving the proper proportions. By this means the solution may be kept in good working order for an in¬definite length of time.
When the solution has dissolved all the gold it can, evaporate it with gentle heat to a small bulk which will solidify when cooled. The resultant yellow salt is the chloride of gold which is soluble in water.
Almost all articles of gold contain traces of silver and this metal may now be observed in the solution in the form of chloride of silver, which is a white substance and insoluble in water, which may be removed, if desired, by pouring off the clear liquid, which holas the gold in solution, leaving behind the white chloride of silver, which should be preserved.
Any dark or brownish substance that will not dissolve is very likely metallic gold formed by the chloride being over heated and should be re-converted into chloride.
A solution of gold forms upon the addition of ammonia, a brown precipitate which, when dry, is one of the most powerful and dangerous ex plosives known, and \Wich detonates with the least friction or percussion. One little accident of this kind will put a sudden stop to any further experiments, therefore great care should be taken to prevent its formation, or if formed] to prevent its becoming dry.
The gilding solution is prepared as follows: Dissolve one pennyweight of chloride of gold in a gallon and a half of water; add nine ounces of caustic potash, one ounce of carbon-l ate of potash, and half an ounce of cyanide ofl potash. This solution should be used very hot, but not quite at the boiling point.
The previously cleaned articles of copper or brass are immersed for a short time in this solution, when they should be taken out and dried. Should a thicker coating be desired they should then be dipped in the cyanide of mercury solution (see page 40) and then after rinsing them, be immersed in the gilding solu¬tion again. By repeating this operation several times a very thick deposit may be obtained capable of resisting the action of the strongest acids for a long time.
This process of gold plating is more particularly adapted to the plating of articles not sub¬ject to much handling, as generally only a very thin coating is obtained by it. The work done by this method, however, looks fully as well as that done by the battery process, and to those having no knowledge ot the art of electro metallurgy is somewhat more simple.
The solution also improves with constant usage, acquiring a greenish tint from the presence of copper dissolved from the articles that have been plated in it. This however, does not interfere with its working unless there is a great deal of it held in solution , then it may be deposited with the gold, and impart a darker color to it.
As the solution gradually loses its gold by being deposited, it is necessary to add, from time to time, a small quantity of chloride of gold dissolved in a little water, 4in order to strengthen it, and after three or four such additions it may be necessary to add a small amount of the other salts, always preserving the proper proportions. By this means the solution may be kept in good working order for an in¬definite length of time.
SILVER PLATING BY THE BATTEEY PROCESS,HOW TO MAKE SILVER PLATING BY THE BATTEEY PROCESS?
Quite a number of the salts of silver have been used in forming solutions for silver plating by means of the electric current, all of which have proved more or less successful, but the solution that has the best stood the test of time and experience, is the commonly called cyanide solution, and which may be formed either by chemical means, or by means of an electric cur¬rent. The former method, we think, is to be preferred, especially when the operation is to be conducted by those having but little experience in such matters. To prepare the solution by this method, make a solution of nitrate of silver in the proportion of about one pint of water to each half ounce of nitrate of silver; also have prepared a solution of cyanide of potassium in the proportion of about two ounces of cyanide of potassium to one quart of water, which should be added to the solution of nitrate of silver as long as any precipitate is formed (which is the cyanide of silver.) Should too much be added some of this precipitate will be redis solved and wasted. This will be indicated by a clear and slightly discolored tint being imparted to the liquid, where the cyanide of potassium solution passes. Should this be the case, add a weak solution of nitrate of silver in small quantities at a time, and at the same time stirring the liquid gently as long as it produces a light cloudy appearance. This amount of care is necessary in order that all of the silver may be utilized, as when too much or too little of the cyanide solution is added, some of the silver remains held in the solution. In the former case, in the shape of the double cyanide of silver and potassium, and when too little is added the silver remains in the clear portion of the solution in the form of nitrate of silver, but when just the proper amount is added, all of the silver is precipitated in the form of the simple cyanide of silver. After the exact neutral paint has been attained, allow the liquid to set¬tle, and pour off the clear liquid, carefully preserving the precipitate which should be well washed by adding a quantity of water, stirring oo
it up thoroughly, and after it has settled pour off the clear liquid, repeating the operation several times until all traces of acid have been removed. The wash waters, as well as the clear liquid first poured off should be preserved and tested in order to recover any traces of silver they may contain. Next add to the wet precipitate a strong solution of cyanide of po¬tassium until barely the whole of it is dissolved, leaving a clear and light amber colored liquid. The cyanide solution should be added in small quantities at a time, and the solution thoroughly stirred upon each addition, then allow it to settle. Should any of the precipitate then remain undissolved, add a little more of the cyanide solution, stir briskly, and allow it to settle, re-peating the operation until barely the whole is dissolved, and finally having observed how s much of the cyanide of potassium solution was required to merely dissolve the precipitate, add about one third teTone half as much more of it, in order to form what is called "free cyanide," and then add enough water to dilute the whole to the proportion of about two ounces of nitrate of silver per gallon or more of the solution. The solution is then ready for immediate use.
There are also quite a number of methods other than this oi making the cyanide solution, but all of them necessitate the introduction of various impurities that are often highly detrimental ; for instance, suppose we add a solution of cyanide of potassium to a solution of oxide of silver as long as it will dissolve, and then add the usual amount of free cyanide part of the cyanide of potassium will be converted into caustic potash, or if chloride of silver be used instead of the oxide, part of the cyanide of potassium will be converted into chloride of potash, or if the nitrate of silver be used, it will produce almost an equal amount of the nitrate of potash as an impurity in the solution. Nor is this process an economical one by any means, as it requires exactly the same amount of cyanide of potassium to convert it into the plating solution as where the solution is made by the method we have first given, and besides it has the very great disadvantage of introducing impurities very detrimental to the satisfactory working of the solution.
The strength of silver plating solutions may vary greatly without materially affecting their operation, some platers doing excellent work
with solutions containing half an ounce of silver per gallon, and others using solutions containing several ounces of silver, and almost as many pounds of cyanide of potassium. A good working solution should contain from one to three ounces of silver per gallon, converted into cyanide, and from thirty to fifty per cent, of free cyanide. A good solution should not have a corroding effect on the base metals because it is those metals we wish to plate, and if the solution should have a corroding effect upon them, it will infallibly cause the deposit to strip and scale off. The cyanide silver plating solution may be made by the battery process, with but very little trouble, and some electro platers prefer this method to any other, but while it possesses the advantage of simplicity, it also has the disadvantage of forming a small quantity of potash in the solution. This, however, may be remedied by the addition of a small quantity of the strongest prussic acid, which converts the caustic potash into cyanide. To make the solution by this process, make a moderately strong solution of cyanide of potas¬sium and suspend in it a large anode and a small cathode of silver and then pass a strong
current of electricity through it until a clean sheet of copper substituted for a short time for the small silver cathode, receives a good deposit of silver, or until the solution contains about one ounce of silver per gallon which may be determined by weighing both the anode and the cathode before placing them in the solution and then weighing them from time to time, until the proper amount of silver is known to have been dissolved, the solution is then ready for use.
The silver deposited by these solutions has a frosted appearance, and must be burnished in order to make them bright, or they may be placed in a specially prepared solution in order to deposit a coating of bright silver upon them.
This brightening solution is prepared by tak¬ing one pint of the ordinary silver plating solu¬tion, containing about two pounds of cyanide of potassium per gallon, and add to it two ounces of bisulphide of carbon, two of strong liquor ammonia and one of ether, and shake well. Let it stand at least twenty-four hours, shaking it occasionally, and then add the clear liquid to the ordinary silver plating solution, with gentle stirring in the proportion of one ounce to every ten gallons. This would make less than a small tea spoon full per gallon. This brightening mixture should be added in the above propor¬tions about every other day, but great care must be observed that too much is not used, as more solutions have been ruined by the excess of the brightening solution, than by all other causes put together. It is best to add but very little at first, and if from the Working of the solution, you conclude it needs more, then add a very little more taking care to use only the very least possible amount necessary to produce the desired effect. If too much is added, it will cause the articles to have a dull and dark appearance, and perhaps to have dark streaks or spots on them. As often as a quantity of the brightening liquid is used, add a similar amount of the ordinary plating solution, or the same amount of a solution of cyanide of potassium, containing two pounds of cyanide of potassium per gallon. Another brightening solution is prepared by taking one quart of ordinary silver plating liquid containing about a half pound of cyanide of potassium, and adding to it two ounces of bisulphide of carbon, shaking well, and then set aside for a day or two, and adding to the ordinary plating solution in the same proportion as the first liquid we mention, always replacing the amount used by a similar amount of the ordinary silver plating solution, and shaking well. The "bright" solution is only used to finish articles in they having previously received a deposit in the ordinary plat¬ing solution, and then transferred immediately to the "bright" solution. Now having de¬scribed the different methods of making the solutions, we will give the reader a few practical hints as to their management.
Copper, brass, and German silver become coated with silver much easier than any other metal, and for this reason all articles of other metals should, if possible, first receive a deposit of copper before attempting to plate them with silver. This, however, is not absolutely necessary, when plating by means of the electric cur¬rent. All articles must of course be made perfectly clean before attempting to plate them and when the cleaning operation has been con-cluded, great care must be taken to prevent them coming in contact with anything that would tarnish them in the least, handling them only with metallic hooks or tongs and never with the naked hand.
Articles of iron and steel are first immersed in a hot and strong potash solution, then dipped for a short time only in a liquid prepared as follows • Take one pint of water, add to it slowly two ounces of sulphuric acid that has had a small piece of zinc dissolved in it and then add one ounce of nitric acid ; This should give the articles a clean bright appearance.
They may then be plated with copper in a cyanide solution as previously described or they may be placed in the ordinary silver plating solution, using a strong battery of considerable "quantity" at first, or until they have acquired a thin deposit, when the battery should be reduced to the ordinary strength, until the deposit is sufficiently heavy.
All articles should be suspended in the solution by means of a wire or hook of the same or similar metal, small articles may be strung on a wire of the same metal as the contact of different metals in the solution is apt to leave a stain.
Articles of copper, brass and German silver, after being thoroughly cleaned by means of the potash and acid solutions, should be immersed in the following solution and then well rinsed in clean water just previous to placing them in the silver solution : Dissolve one ounce of mercury in a mixture composed of nitric acid one part and water three parts, add no more mercury than the acid will dissolve, dilute it with as much more water and add a strong solution of cyanide of potassium as long as it forms a precipitate but no longer. Collect the precipitate and wash it two or three times with clear water, then add to it with occasional stirring a strong solution of cyanide of potassium until it is all dissolved, then add a little more of the cyanide solution and enough water to make the whole measure a gallon. This solution will cover the articles with a thin coating of mercury and will generally insure a firm adherent deposit.
The articles should not remain in the murcuric solution any longer than is necessary to make them look white, and should be well rinsed in water after taking them out, in order to remove all excess of it.
The solution will last a long time, but it final¬ly becomes weak and impure from continued use, and blackens the articles immersed in it. It is then better to make a new solution than to try to revive the old one, almost any salt of mercury may be dissolved in a solution of cyanide of potassium to be used as a "quick-ing" solution. For instance, dissolve a quantity of red precipitate in an excess of a solution of cyanide of potassium ; that is, add the red precipitate as long as the cyanide solution will dissolve it; then add a small quantity of the cyanide solution.
The mercuric solution may be prepared in a number of ways, but the result is practically the same, viz. : The forming of a solution of the double cyanide of mercury and potassium.
The brightening solution works slower and requires a stronger battery than the ordinary solution; it generally requiring from ten to twenty minutes for the articles to become wholly bright. The deposit is also much harder.
When the articles are once placed in the solution they must not be moved or disturbed until the operation is completed, and where a number of articles are being brightened at the same time none of them must be taken out or disturbed in any way until all of them have be¬come bright.
When the articles have become sufficiently bright disconnect them from the battery and
remove them from the solution and place them immediately in boiling water and allow them to remain there a few minutes, then take them out and dry them.
it up thoroughly, and after it has settled pour off the clear liquid, repeating the operation several times until all traces of acid have been removed. The wash waters, as well as the clear liquid first poured off should be preserved and tested in order to recover any traces of silver they may contain. Next add to the wet precipitate a strong solution of cyanide of po¬tassium until barely the whole of it is dissolved, leaving a clear and light amber colored liquid. The cyanide solution should be added in small quantities at a time, and the solution thoroughly stirred upon each addition, then allow it to settle. Should any of the precipitate then remain undissolved, add a little more of the cyanide solution, stir briskly, and allow it to settle, re-peating the operation until barely the whole is dissolved, and finally having observed how s much of the cyanide of potassium solution was required to merely dissolve the precipitate, add about one third teTone half as much more of it, in order to form what is called "free cyanide," and then add enough water to dilute the whole to the proportion of about two ounces of nitrate of silver per gallon or more of the solution. The solution is then ready for immediate use.
There are also quite a number of methods other than this oi making the cyanide solution, but all of them necessitate the introduction of various impurities that are often highly detrimental ; for instance, suppose we add a solution of cyanide of potassium to a solution of oxide of silver as long as it will dissolve, and then add the usual amount of free cyanide part of the cyanide of potassium will be converted into caustic potash, or if chloride of silver be used instead of the oxide, part of the cyanide of potassium will be converted into chloride of potash, or if the nitrate of silver be used, it will produce almost an equal amount of the nitrate of potash as an impurity in the solution. Nor is this process an economical one by any means, as it requires exactly the same amount of cyanide of potassium to convert it into the plating solution as where the solution is made by the method we have first given, and besides it has the very great disadvantage of introducing impurities very detrimental to the satisfactory working of the solution.
The strength of silver plating solutions may vary greatly without materially affecting their operation, some platers doing excellent work
with solutions containing half an ounce of silver per gallon, and others using solutions containing several ounces of silver, and almost as many pounds of cyanide of potassium. A good working solution should contain from one to three ounces of silver per gallon, converted into cyanide, and from thirty to fifty per cent, of free cyanide. A good solution should not have a corroding effect on the base metals because it is those metals we wish to plate, and if the solution should have a corroding effect upon them, it will infallibly cause the deposit to strip and scale off. The cyanide silver plating solution may be made by the battery process, with but very little trouble, and some electro platers prefer this method to any other, but while it possesses the advantage of simplicity, it also has the disadvantage of forming a small quantity of potash in the solution. This, however, may be remedied by the addition of a small quantity of the strongest prussic acid, which converts the caustic potash into cyanide. To make the solution by this process, make a moderately strong solution of cyanide of potas¬sium and suspend in it a large anode and a small cathode of silver and then pass a strong
current of electricity through it until a clean sheet of copper substituted for a short time for the small silver cathode, receives a good deposit of silver, or until the solution contains about one ounce of silver per gallon which may be determined by weighing both the anode and the cathode before placing them in the solution and then weighing them from time to time, until the proper amount of silver is known to have been dissolved, the solution is then ready for use.
The silver deposited by these solutions has a frosted appearance, and must be burnished in order to make them bright, or they may be placed in a specially prepared solution in order to deposit a coating of bright silver upon them.
This brightening solution is prepared by tak¬ing one pint of the ordinary silver plating solu¬tion, containing about two pounds of cyanide of potassium per gallon, and add to it two ounces of bisulphide of carbon, two of strong liquor ammonia and one of ether, and shake well. Let it stand at least twenty-four hours, shaking it occasionally, and then add the clear liquid to the ordinary silver plating solution, with gentle stirring in the proportion of one ounce to every ten gallons. This would make less than a small tea spoon full per gallon. This brightening mixture should be added in the above propor¬tions about every other day, but great care must be observed that too much is not used, as more solutions have been ruined by the excess of the brightening solution, than by all other causes put together. It is best to add but very little at first, and if from the Working of the solution, you conclude it needs more, then add a very little more taking care to use only the very least possible amount necessary to produce the desired effect. If too much is added, it will cause the articles to have a dull and dark appearance, and perhaps to have dark streaks or spots on them. As often as a quantity of the brightening liquid is used, add a similar amount of the ordinary plating solution, or the same amount of a solution of cyanide of potassium, containing two pounds of cyanide of potassium per gallon. Another brightening solution is prepared by taking one quart of ordinary silver plating liquid containing about a half pound of cyanide of potassium, and adding to it two ounces of bisulphide of carbon, shaking well, and then set aside for a day or two, and adding to the ordinary plating solution in the same proportion as the first liquid we mention, always replacing the amount used by a similar amount of the ordinary silver plating solution, and shaking well. The "bright" solution is only used to finish articles in they having previously received a deposit in the ordinary plat¬ing solution, and then transferred immediately to the "bright" solution. Now having de¬scribed the different methods of making the solutions, we will give the reader a few practical hints as to their management.
Copper, brass, and German silver become coated with silver much easier than any other metal, and for this reason all articles of other metals should, if possible, first receive a deposit of copper before attempting to plate them with silver. This, however, is not absolutely necessary, when plating by means of the electric cur¬rent. All articles must of course be made perfectly clean before attempting to plate them and when the cleaning operation has been con-cluded, great care must be taken to prevent them coming in contact with anything that would tarnish them in the least, handling them only with metallic hooks or tongs and never with the naked hand.
Articles of iron and steel are first immersed in a hot and strong potash solution, then dipped for a short time only in a liquid prepared as follows • Take one pint of water, add to it slowly two ounces of sulphuric acid that has had a small piece of zinc dissolved in it and then add one ounce of nitric acid ; This should give the articles a clean bright appearance.
They may then be plated with copper in a cyanide solution as previously described or they may be placed in the ordinary silver plating solution, using a strong battery of considerable "quantity" at first, or until they have acquired a thin deposit, when the battery should be reduced to the ordinary strength, until the deposit is sufficiently heavy.
All articles should be suspended in the solution by means of a wire or hook of the same or similar metal, small articles may be strung on a wire of the same metal as the contact of different metals in the solution is apt to leave a stain.
Articles of copper, brass and German silver, after being thoroughly cleaned by means of the potash and acid solutions, should be immersed in the following solution and then well rinsed in clean water just previous to placing them in the silver solution : Dissolve one ounce of mercury in a mixture composed of nitric acid one part and water three parts, add no more mercury than the acid will dissolve, dilute it with as much more water and add a strong solution of cyanide of potassium as long as it forms a precipitate but no longer. Collect the precipitate and wash it two or three times with clear water, then add to it with occasional stirring a strong solution of cyanide of potassium until it is all dissolved, then add a little more of the cyanide solution and enough water to make the whole measure a gallon. This solution will cover the articles with a thin coating of mercury and will generally insure a firm adherent deposit.
The articles should not remain in the murcuric solution any longer than is necessary to make them look white, and should be well rinsed in water after taking them out, in order to remove all excess of it.
The solution will last a long time, but it final¬ly becomes weak and impure from continued use, and blackens the articles immersed in it. It is then better to make a new solution than to try to revive the old one, almost any salt of mercury may be dissolved in a solution of cyanide of potassium to be used as a "quick-ing" solution. For instance, dissolve a quantity of red precipitate in an excess of a solution of cyanide of potassium ; that is, add the red precipitate as long as the cyanide solution will dissolve it; then add a small quantity of the cyanide solution.
The mercuric solution may be prepared in a number of ways, but the result is practically the same, viz. : The forming of a solution of the double cyanide of mercury and potassium.
The brightening solution works slower and requires a stronger battery than the ordinary solution; it generally requiring from ten to twenty minutes for the articles to become wholly bright. The deposit is also much harder.
When the articles are once placed in the solution they must not be moved or disturbed until the operation is completed, and where a number of articles are being brightened at the same time none of them must be taken out or disturbed in any way until all of them have be¬come bright.
When the articles have become sufficiently bright disconnect them from the battery and
remove them from the solution and place them immediately in boiling water and allow them to remain there a few minutes, then take them out and dry them.
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