4211. Hyposulphite of Soda

4211.     Hyposulphite of Soda. Mix together 1 pound dried carbonate of soda and 10 ounces flowers of sulphur, and slowly heat the powder in a porcelain dish until the sulphur melts; stir freely, to expose it to the atmosphere, until the incandescence flags, then dissolve the mass in water, and immediately boil the filtered liquid with some flowers of sulphur; lastly, carefully concentrate the solution for crystallization. (Cooley.)

It may also be prepard by dissolving 8 parts carbonate of soda in 16 parts water; add 1 part sublimed sulphur, and pass sulphurous acid gas, in excess, into the solution; boil the liquid in a glass matrass for a few minutes, filter, gently evaporate the filtrate to 1/8 its volume, and set it aside in a cool place to crys-tallize. (Paris Codex.)

4212. Tungstate of Soda

4212. Tungstate of Soda. This is formed by dissolving tungstic acid in a concentrated solution of pure soda. Tungstic acid is a yellow powder obtained by digesting native tungstate of lime, finely powdered, in nitric acid. It forms tungstates with metals and bases.

4213. Potassio-Tartrate of Soda

4213. Potassio-Tartrate of Soda. Known in commerce as Seignettc's or Rochelle salt. Dissolve 12 ounces carbonate of soda in 2 quarts boiling water; add gradually 16 ounces bitartrate of potassa in fine powder. Strain, evaporate to a pellicle or crust (see No. 9 (Crystallization)), and set it aside to crystallize. The mother liquor may be further evaporated for a second supply of crystals. (Cooley.) Tho U. S. Pharmacopoeia adopts the same method, but directs 5 pints of boiling water to be used.

4214. Bromide of Sodium

4214.    Bromide of Sodium. This is now employed to a great extent instead of bromide of potassium; it is more active than the latter, is more quickly absorbed, and more regularly eliminated. To prepare it pure and in large quantities tho following method is recommended: Bromide of ammonium is decomposed by an equivalent quantity of caustic or carbonate of soda, which, of course, must be free from sulphuric and hydrochloric acids. The solution yields, after evaporation, small cubes of anhydrous bromide of sodium.

4215. Chloride of Sodium

4215.    Chloride of Sodium. This is a muriate of soda, or common table salt, and is largely obtained by tho evaporation of sea water, or from tho water of salt springs. It dissolves in about 2i parts of water at 60° Fahr.; is insoluble in pure alcohol; fuses at a red heat; and at a higher temperature becomes volatile.

4216. Iodide of Sodium

4216.    Iodide of Sodium. This is obtained from soda in tho same manner as iodide of potassium. (See No. 4203 (Iodide of Potassium).)

4217. Nitro-Prusside of Sodium

4217.    Nitro-Prusside of Sodium. To 213 parts of powdered ferroprussiate of potash, in a porceliain basin, add 450 parts of nitric acid of 1.42 density (or 3371/2 parts at 1.50), adding all tho acid at once. When dissolved, transfer to a bolt-head, and digest in a water-bath until tho solution precipitates salts of protoxide of iron of a slate color. Neutralize, when cold, with a cold solution of carbonate of soda; then boil, and separate the precipitate by filtration. Evaporate tho liquid again, filter, and allow the nitrates of potash and soda to crystallize out. Evaporate the liquid again, and remove tho prismatic crystals of nitro-prusside as they form. They may be dissolved in water and recrystallized by cooling.