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.
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