Amalgam, Ammonium. An unstable compound produced when a globule of mercury is placed in a small cavity formed in a piece of sal ammoniac, and the negative pole of a powerful galvanic battery is brought into contact with the metal, and the positive pole, with the ammoniacal salt. In a few seconds the new compound (ammonium amalgam) of the consistence of butter is formed. On withdrawing the influence of the battery, the whole returns to its former condition. By putting an amalgam of sodium into the moistened cavity of the sal ammoniac, similar results are obtained. The phenomena attending the formation of this new substance have been urged as evidence of the existence of the theoretical basic radicle AMMONIUM.
Amalgam, Elec′trical. Prep. 1. Take zinc and grain-tin, of each, 1 oz.; melt them in an iron ladle, remove it from the fire, and add of mercury (hot), 3 oz.; stir the whole well together with an iron rod, pour it into a well-chalked wooden box, and agitate it violently until cold; or, instead of this, it may be briskly stirred until cold, and then powdered. It should be preserved in a corked glass bottle.
2. (La Baumé.) Zinc, 2 oz.; grain-tin, 1 oz.; bees’ wax, 1⁄2 oz.; melt, add of mercury, 6 oz., and otherwise proceed as before. Preferred by some to all other mixtures.
3. Zinc, 2 oz.; mercury, 5 oz.
Use. To cover the cushions of electrical machines. A little of the powder is poured on a piece of paper, crushed smooth with a flat knife, and then spread thinly on the surface of the cushion or rubber, previously slightly smeared with tallow; or the powder may be rubbed down with a little tallow, prior to the application of it.
Amalgam, Gild′ing. Syn. Amalgam of gold.
Prep. Take of grain-gold, 1 part; mercury, 8 parts; put them into a small iron saucepan, or ladle, and apply a gentle heat, using a smooth piece of iron as a stirrer; when the solution or combination is complete, pour it out on a clean plate or smooth stone slab.
Use. To gild brass, copper, &c., in the common process of wash or fire-gilding. A less proportion of gold than the above is used when a thin and cheap gilding is required; as by increasing the quantity of the mercury the same weight of the precious metal may be extended over a much larger surface.
Amalgam, Sil′vering.—a. For METALS. Syn. Amalgam of silver. Prep., Uses, &c. As the last, but substituting silver for gold.
b. For GLASS. Prep. 1. Lead, tin, and bismuth, of each, 1 oz.; bees’ wax or resin 1⁄4 oz.; melt, skim off the dross, cool to the lowest point at which the mixture will remain liquid, and add of quicksilver 10 oz.; mix well with an iron rod.