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Gold Coloring Solution

Take 1 ounce nitrate of soda, and 1/2 ounce chloride of sodium, and dissolve in a slight excess of

If 100 grains of the substance or liquid warm water, afterwards adding to the soluunder test be taken for examination, the tion about 5 drachms hydrochloric acid. weight in grains of the dried precipitate will The solution should be kept boiling while the give the percentage of gold contained in the work is in it. sample.

3193. Το Obtain Gold Chemically Pure. Dissolve gold in nitromuriatic acid (a mixture of 1 part nitric acid with 2 parts nuriatic acid, and called aqua regia); by adding to the gold solution a solution of protosulphate of iron, the pure gold is precipitated in the form of a brown powder, which should be thoroughly washed to free it from acid, and then dried. In this form it is ready to mix by fusion with other metals; or the powder can be reduced to solid metallic form by melting in a crucible, with a charcoal fire, sprinkling occasionally into the crucible a little saltpetre and potash as a flux. The gold will form a button at the bottom.

3200. To Clean Gold after it is Soldered. Put it through the same process as silver (see No. 3222), but, instead of alumwater, boil it in wine and sal-ammoniac. 3201. Το Restore the Color of Gold after Soldering. Boil the gold, after soldering, in diluted oil of vitriol; rinse in clean water, polish with Tripoli mixed in oil (sweet oil is best), wash and gloss with crocus on a clean cloth.