All articles to be plated must first be made scrupulously clean, in order to obtain a good firm deposit. A great many failures may be attributed to the neglect of this very important step. They should first be filed or scraped, or otherwise made as smooth as possible, then immersed for a short time, in a strong and hot solution of potash, (concentrated lye) and then rinsed well in clean water.
A very good scraper can be easily made by grinding down the sides of a three cornered file until it is perfectly smooth, and finishing up on an oil stone, thus leaving three sharp cutting edges. Articles that have been soldered, must not be allowed to remain long in the potash solution, or a portion of the tin contained in the solder will be dissolved, and deposited on the articles, should they be copper or brass, and blacken them. Articles of copper, or brass, require only a few seconds immersion, those of iron, or steel, a somewhat longer time. All articles should be well washed in clean water, immediately after taking them out of the potash solution, after which they should be treated with some of the different acid solutions, in order to more fully prepare the surface for the depositing solution. All articles of copper, brass, or German silver, should be dipped into a solution consisting of water four parts, sulphuric acid four parts, nitric acid two parts, to which a very small quantity of muriatic acid may be added. Articles of iron should be dipped in a mixture composed of one part of sulphuric acid and fifteen or twenty parts of water, and then well washed. Articles of lead, brittannia metal, or pewter, after having been treated with the potash solution and rinsed may be placed at once in the plating solution. It is a much better plan, however, to coat them, and articles of iron and steel also, with a thin film oi copper by means of one of the following solutions before attempting to plate them with either gold, silver or nickel. For depositing a thin coating of copper on iron or steel use a weak and slightly acidulated solution of sulphate of copper, (blue vitriol) rub the titikhs briskly with a cloth moistened with this liquid, and as soon as they have the desired appearance, wash them well and dry them quickly ; or they may simply be immersed in the liquid for a short time, and then thoroughly washed, and dried. This solution is not adapted for any other metals except iron and steel, and is not always certain • in its operation. The surest, and best way is to use a battery and an alkaline solution, which may be prepared in the following manner: Add to a solution of sulphate of copper, a solution of cyanide of potassium just as long, but no longer than it forms a precipitate ; the cyanide solution should be added slowly, and towards the last in small quantities at a time, with frequent stirring, carefully observing when it no longer forms a precipitate, which is cyanide of copper. Allow it to settle, and pour off the clear liquid, wash the precipitate well by filling the vessel with water, stirring it up, and aftei it has settled again pouring off the water, repeating the operation several times, in order to remove all traces of acid, then add to the wet cyanide of copper, a little more of a solution of cyanide of potassium than is required simply to dissolve it, that is, add the ^cyanide of potassium solution, to the wet cyanide of copper, until it is all dissolved ; then add a little more of the cyanide solution to form what is termed "free cyanide." This solution should be used at a temperature of about 1500 Fahr. A battery of from one to three cells, such as are used in all telegraph offices, will be sufficient for all ordinary opera tions. To use this solution, immerse in it a clean sheet of copper and attach it to the wire leading from the copper pole of the battery, and the previously well cleaned articles of iron, steel, lead, brittannia metal, and in fact almost any metal to the wire leading from the zinc pole of the battery. The articles should be immersed in the solution before being connected to the battery, and the wire should be detached from them before taking them out of it, The amount of battery should be adjusted to the amount of surface presented by the articles to be plated. The smaller the articles, the less battery power will be required. A number of small articles may be attached to each other, or to the same wire, and be plated at one time. If too much battery be used, the copper will be deposited in the form of a dark metallic powder. This solution is rather difficult to manage, and is more expensive than a simple acidulated solution of sulphate of copper. This latter solution, however, cannot be used to plate iron, steel, lead, brittannia metal, etc., unless they have previously received a thin deposit of copper in the cyanide solution. The sulphate solution is used in precisely the same manner as the cyanide solution, and where heavy deposits are desired, it is much to be. preferred. In coppering articles in this way, preparatory to plating them with another metal, a thin deposit will be sufficient, but as we have stated before, the sulphate solution will not answer, unless the articles have previously received a thin deposit of copper, and we must per force first use the cyanide solution, or in the case of iron and steel resort to the rather uncertain method of rubbing them with a rag, moistened with a slightly acidulated solution of the sulphate. After removing the articles from the solution, they should be well washed and examined, and if any imperfections be discovered, the cleaning and scouring operation will have to be done over again, and tiV plating repeated, but by using a proper amount of care the first attempt will generally prove successful.
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