To separate gold from gilded metallic articles, dip them in a concentrated solution of sal-ammoniac in vinegar which has been heated to a dark red heat. Then immerse them in dilute sulphuric acid, which will cause the gold to separate in thin scales. If it is desired to obtain the gold in a coherent form, fuse the scales with saltpeter and borax.
You will have great difficulty in separating lead from zinc. If you have the necessary appliances for heating the mass sufficiently the zinc will partially evaporate and leave the lead on being treated. If the whole is granulated the zinc could be dissolved by acids. Zinc being of lighter specific gravity than lead it will float on the latter when properly heated, and to a certain extent can be skimmed off. You will find all these processes troublesome, and in the end not entirely satisfactory.
In order to give tin a sepia-bronze appearance, brush the article with the following solution, viz., 1 part of platinum chloride in 10 parts of water. The coating should be allowed to dry, then rinsed in water, again allowed to dry and then brushed with a soft brush until the requisite luster makes its appearance.
To sharpen files, a metal sheet covered with a thin layer of charcoal is fastened upon the file, protecting the edges. This combination is laid into a solution of six parts of nitric acid and three parts of sulphuric acid in a hundred parts of water. The acid eats away all the inner parts of the file, leaving the protected edges unchanged, which are then sharpened for use.
Silver carbonate is a precipitation formed by bringing together solutions of nitrate of silver and potash.
Horn silver is obtained by the addition of hydrochloric acid to a solution of nitrate of silver.
To give a silver color to bronze proceed to the dissolution, in a vessel that is well glazed, of:
1 1/2 drachms Tartar Emetic.
1 1/2 ounces Pulverized Cream of Tartar in 1 quart Hot Water, and add to this solution;
1 ounce Pulverized Antimony, 1 3/4 ounces Hydro-chloric Acid.
The articles to be coated are immersed in this solution, which is to be heated to the boiling point and allowed to boil for from 15 to 30 minutes; at the end of this time they will be given a beautiful, lustrous coating.
A bath prepared by dissolving 3 1/2 drachms nitrate of silver in 7 ounces of water and adding 7 drachms of cyanide of potassium may be used for this purpose. This solution is to be poured into 21 ounces of water, wherein 3 1/2 drachms of common salt have been previously dissolved. The cat-iron intended to be silvered by the solution should, after having been cleaned, be placed for a few minutes in a bath of dilute nitric acid just previous to being placed in the silvering fluid.