4099. Tests for Copper Solutions

4099.   Tests for Copper Solutions. The solutions of copper possess a blue or green color, which they retain, even when considerably diluted with water.

With caustic potassa they give a light blue bulky precipitate, turning blackish-brown or black on boiling the liquid.

Ammonia and carbonate of ammonia produce a bluish-white precipitate, soluble in excess of ammonia, yielding a rich deep blue solution.

The carbonates of potassa give a similar precipitate to the last, but insoluble in excess of the precipitate.

Ferrocyanide of potassium gives a reddish-brown precipitate. Sulphuretted hydrogen and hydrosulphuret of ammonia give a blackish-brown or black one.

A polished rod of iron, on inmersion in an acidulated solution, quickly becomes coated with metallic copper.

4100. Delicate Test for Iron and Copper

4100.     Delicate Test for Iron and Copper. The alcohol tincture of logwood will produce a blue or bluish-black tint in water which has been run through iron or copper pipes, when neither tincture of galls, sulphocyanide, nor the ferrid and ferrocyan-ides of potassium show any reaction.

4101. Acetate of Lead

4101.     Acetate of Lead. Acetate of lead should be completely soluble in distilled water, and when the lead is exactly precipitated with dilute sulphuric acid, or by sulphuretted hydrogen, the clear supernatant liquid should be wholly volatilized by heat without residue. Sulphuric acid poured on acetate of lead evolves acetic vapors. Acetate of lead is powerfully astringent. Take 4 pounds 2 ounces oxide of lead (litharge), acetic acid (specific gravity 1.048), and distilled water, of each 4 pints; mix tho fluids, add the oxide, dissolved by a gentle heat, strain, evaporate, and crystallize. On the largo scale it is usually prepared by gradually sprinkling oxide of lead into strong vinegar, heated in a copper boiler rendered negative-electric by having a large flat piece of leat soldered within it, constant stirring being employed until tho acid is saturated, when tho mother liquors of a former process may be added, the whole heated to the boiling point, allowed to settle till cold, decanted, evaporated to about the specific gravity 1.236 or 1.2G7, and then run into salt-glazed stoneware vessels to crystallize. The best proportions are, finely powdered litharge 13 parts, and acetic acid specific gravity 1.0482 to 1.0484, 23 parts. These ingredients should produce about 38i parts of crystallized sugar of lead. A very slight excess of acid should be preserved in the liquid during the boiling and crystallization, to prevent the formation of any basic acetate, which would impede the formation of regular crystals.

4102. Chloride of Lead

4102.     Chloride of Lead. This is a white crystalline powder, called also muriate of lead. Precipitate a solution of 19 ounces acetate of lead in 3 pints boiling distilled water, with a solution of 6 ounces chloride of | sodium in 1 pint boiling water; when cold, . wash and dry the precipitate. It may bo obtained in brilliant colorless needle-shaped crystals, by dissolving finely powdered litharge in boiling dilute hydrochloric acid. Filter while hot, and the crystals form on cooling.