To Alloy Gold.—For 18 karat gold, melt together 18 gold, 4 copper, 2 sil ver, if the metals are pure. Or 19i gold coin, 3 copper, 1 silver.
For 16 karat, if pure, 16 gold, 5i silver, copper. Or 17 gold coin, 5 copper, 2 silver.
For 12 karat, 26 gold coin, 13i cop per, 8i silver.
For 4 karat, 18 copper, 4 gold, 2 silver. This last, of course, is used only for cheap jewelry, but it is hard er and more durable than the better grades, and is more suitable for stick pins and the like.
To Make Gold Powder.—Mix gold leaf with honey or a solution of gum arable, and rub the mixture in a mor tar until the gold is sufficiently fine. Dilute the solution with water, and decant or wash on filter paper until the pure gold remains.
Alloy of Gold.—Melt 71 parts of pure gold and add part of plati num. This alloy is whiter than gold, but ductile, elastic, and much less perishable than pure gold or the bet ter grades of gold used for jewelry. It melts readily, however, and is solu ble in nitric acid.
Artificial Gold.—Sixteen platinum, 7 copper, I zinc. Melt in a crucible, cover with powdered charcoal, and mix with saltpeter and sal ammoniac.
Or 4 platinum, 2i copper, 1 zinc, 2 tin, 11 lead.
Or 2 platinum, 1 silver, 3 copper. If the resulting mixture is not per fectly homogeneous, it may be hard and brittle. In that case melt down with sal ammoniac. Repeat if neces sary. These alloys very closely re semble gold.
Gold Solder.—Six gold, 1 silver, 2 copper. Use the pure metals. Melt together.
Or 14 gold, 1 silver, 1 copper. This is a soft gold solder which may be made softer by adding brass, but this makes it liable to oxidize.
Or 7 silver, 1 copper with borax.
Or 2 gold, 1 silver, 1 copper.
Or 3 gold, 3 silver, 1 copper, zinc. Platinum Solder. — Use pure gold with borax.
Gold Amalgam.—This consists of 8 parts gold to 1 part mercury, and is used principally in gilding. Heat in a crucible the gold in thin strips to near the melting point, and add to it the mercury. The two metals will unite, boiling vigorously. When cold, the amalgam is ready to use.
Gilding.—Ou account of its beauty, and the fact that it will not rust or corrode from exposure to the air, a thin film of gold is often applied to silver or cheaper metals, wood, paper, leather, and other materials for deco rative purposes. This may be done
in three different ways: by means of gold powder, gold leaf, or by a solu tion, an amalgam, or a mixture of gold in liquid form.
To Gild Metals.—Dissolve in water 8 ounces of niter, 8 ounces of corn Fion salt, and 5 ounces of alum. Dis solve ounce of gold separately in 1 ounce of aqua regia, and evaporate with gentle heat to dryness. Mix the settlings with alcohol or ether. Dip the articles to be gilded in the niter, salt, and alum solution, and brush them over with the ethereal solution of gold.
Or dip the articles in the ethereal solution. Remove and allow the ether to evaporate.
Steel cutting instruments given a thin coat of gold by this method will be preserved from rust, or lettering may be done by means of this solu tion on iron or steel.
Or the articles may be washed with a solution of nitrate of mercury, and an amalgam of gold and mercury ap plied with a brush. They must then be heated to drive off the mercury in the form of vapor.
Or make a saturated solution of gold and aqua regia, and soak fine linen rags in it until it is all absorbed. Carefully dry these and burn them to tinder. Polish the article to be gilt, dip a brush in a solution of common salt in water, then into this tinder, and rub over the surface of the articles.
Or expose articles of iron, steel, copper, or other hard metal to a blu ing heat. Lay on gold leaf and bur nish gently. Continue the heat and add gold leaf until the desired thick ness has been obtained. Cool and burnish.
Gilding by Amalgam. — Take ounce troy of fine gold, 1 ounce of nitric acid, / ounce of hydrochloric acid, and soft water / ounce. Put all in a glass vessel and heat gently in a double boiler until the fumes cease to rise. Add 30 ounces of water, boil for 9 hours, let it settle, and pour off the clear liquor from the sedi ment for use. Clean and polish the articles to be gilt, and suspend them in this liquor by means of a fine wire or a horsehair. When sufficiently gilt, wash in pure water.