3743. Electro-Gilding Without a Battery

3743. Electro-Gilding Without a Battery. Dissolve 9 parts terchloride of gold in 1000 to 2000 parts pure water; then add 360 parts bicarbonate of potassa, and boil for two hours. The metallic article, if not copper, is covered with a film of copper simultaneously with its being immersed into the boiling gilding liquor, by placing a piece of sheet-copper along with it. As soon as a deposit of copper is observed, the piece of copper is taken out, and the liquor continued boiling until a deep yellow color is obtained. The article is then taken out, washed off with water, and rubbed with a metallic brush. "When the liquor has again become clear by settling and decanting, it is again heated to boiling, the article immersed, while the piece of copper is moved about in the fluid without touching the other. The same operation may be renewed ad libitum, until the desired thickness of gold is obtained.

3744. Plating and Gilding Without a Battery

3744.    Plating and Gilding Without a Battery. "Watts gives the following very useful solution of silver or gold fur plating or gilding without the aid of a battery : Take 1 ounce nitrate of silver, dissolved in 1 quart distilled or rain water. "When thoroughly dissolved, throw in a few crystals of hyposulphite of soda, which will at first form a brown precipitate, but which eventually becomes redissolved if sufficient hyposulphite has been employed. A slight excess of this salt must, however, be added. The solution thus formed may be used for coating small articles of steel, brass, or German silver, by simply dipping a sponge in the solution and rubbing it over the surface of the article to be coated; the silver becomes so firmly attached to the steel (when the solution has been carefully made) that it is removed with considerable difficulty. A solution of gold may be made in the same way, and applied as described. A concentrated solution of either gold or silver, thus made, may be used for coating parts of articles which have stripped or blistered, by applying it with a camel-hair pencil to the part, and touching the spot at the same time with a thin clean strip of zinc.

3745. To Distinguish Gold from its Imitations

3745.    To Distinguish Gold from its Imitations. The ordinary method of testing gold by the touchstone is founded upon the insolubility of this metal in nitric acid. If a mark be made on the touchstone with the article under examination, the gold is not dissolved by this acid, whereas golden colored alloys of inferior value are dissolved and disappear immediately. When articles are very thinly gilded, the detection of the gold in this manner is uncertain, in which case the following method may bo used with advantage. (See No. 3190 (Assay of Gold by the Use of Touch-Stones).)

3746. Test Fluid for Gilded Articles

3746.      Test Fluid for Gilded Articles. A little carbonate of copper is put into a test-tube, and to this is added, drop by drop, pure hydrochloric acid, till the blue powder has dissolved to a clear green fluid, occasionally warming it over a spirit lamp. This concentrated solution of chloride of copper is diluted for use with from 10 to 11 times its volume of distilled water.