4078. Oxide of Silver

4078.      Oxide of Silver. Dissolve 2 parts nitrate of silver, and 1 part hydrate of potassa, each separately, in distilled water; mix the solution, and, after frequent agitation during an hour, collect and wash the precipitate, and dry it by a gentle heat in the shade. This is more strictly the protoxide of silver, and is in tho form of a pale brown powder.

4079. To Reduce Solid Silver from its Chloride

4079.     To Reduce Solid Silver from its Chloride. Mix together the dry chloride of silver in 1/3 its weight of powdered black resin; heat moderately in a crucible until the flame ceases to have a greenish blue color; then increase the heat suddenly until tho silver fuses into a button at the bottom of the crucible. Some parties recommend an addition of a little powdered calcined borax, sprinkled on the surface before increasing the heat. (See No. 3214 (To Purify and Reduce Silver).)

4080. To Prepare Nitrate of Silver from an Alloy of Silver and Copper

4080.    To Prepare Nitrate of Silver from an Alloy of Silver and Copper. Palm's method. When it is desired to prepare nitrate of silver from silver containing copper - coins for example - filter tho nitric acid solution, dissolve tho alloy in nitric acid, evaporate it nearly to the consistence of oil, not to dryness, and add to a part of this concentrated metallic solution, 3/4 part of nitric acid free from chlorine. The silver salt precipitates in the form of crystals and the copper remains in tho solution. Wash the precipitate 2 or 3 times with concentrated nitric acid, and evaporate to dryness. Tho more concentrated the nitric acid, tho more completely is the silver salt precipitated; an acid of 1.250 specific gravity is sufficient, however, to separate completely the two metals. (See No. 321G.)

4081. Sulphate of Silver

4081.     Sulphate of Silver. Prepared by dissolving silver in sulphuric acid containing one-tenth of nitric acid; or by precipitating a solution of the nitrate by another of sulphate of soda. It dissolves in 80 parts of hot water, and falls in small needles as the solution cools. (Cooley). According to Fownes it dissolves in 88 parts boiling water.

4082. Sulphuret of Silver

4082.    Sulphuret of Silver. A greyish-black substance prepared by passing sulphuretted hydrogen gas through a solution of nitrate of silver. It may also be obtained by melting sulphur and silver together.

4083. Tests for Silver in Solution

4083.    Tests for Silver in Solution. Silver is entirely soluble in diluted nitric acid. This solution, treated with an excess of muriate of soda, gives a white precipitate entirely soluble in ammonia water, and a fluid which is not affected by sulphuretted hydrogen. The nitric solution of silver also gives a white curdy precipitate (chloride of silver) with muriatic acid, soluble in ammonia and insoluble in nitric acid, and blackened by exposure to light. It gives white precipitates with solutions of the alkaline carbonates, oxalates, and prussiates. It gives yellow precipitates with the alkaline arsenites and phosphates. With the arsenites, red precipitates. "With the fixed alkalies, brown precipitates. "With sulphuretted hydrogen, a black powder. With phosphorus and metallic copper or zinc, a precipitate consisting of pure silver.