Potassium, Sulphate of. K2SO4. Syn. Potassæ sulphas (B. P., Ph. L., E., & D.). Prep. The sulphate of potassium of commerce is a secondary product of several chemical and manufacturing processes. Thus, the residuum
of the distillation of nitric acid from nitre is dissolved in water, the solution neutralised with carbonate of potassium, and, after defecation, evaporation until a pellicle forms; it is then strained, or decanted, and set aside to crystallise. Or, the residuum is simply ignited, to expel excess of acid, and then dissolved and crystallised as before.
Prop., &c. Anhydrous, heavy, quartz-like crystals; permanent in the air; soluble in 12 parts of water at 60° and in 5 parts at 212° Fahr.; insoluble in alcohol; extremely nauseous, and bitter-tasted. It crepitates on the application of heat; fuses at a red heat, but loses nothing in weight. 100 gr. dissolved in distilled water, on the addition of chloride of barium and hydrochloric acid, furnish 132 gr. of sulphate of barium, dried at a red heat.
Potassium, Bisulphate of. KHSO4. Syn. Potassium-hydrogen sulphate, Acid potassium sulphate; Potassæ bisulphas. Prep. 1. (Anhydrous.) Neutral sulphate of potassium and oil of vitriol, equal parts; hot water, q. s. (not more) to dissolve; anhydrous bisulphate crystallises out, in long delicate needles, as the solution cools. If these are left for several days in the mother-liquor they are redissolved, and crystals of the ordinary hydrated bisulphate are deposited.
2. (Hydrated,)—a. (Ph. L. 1836.) Salt left in distilling nitric acid, 2 lbs.; boiling water, 3 quarts; dissolve; add of sulphuric acid 1 lb.; concentrate by evaporation, and set the liquid aside, so that crystals may form.
b. (Ph. D.) Sulphate of potassium (in powder), 3 oz.; sulphuric acid, 1 fl. oz.; mix them in a porcelain capsule, and expose it to a heat capable of liquefying its contents, until acid vapours cease to be evolved; powder the residuum, and preserve it in a well-stopped bottle.
Prop., &c. Sour and slightly bitter-tasted rhombic prisms; soluble in about 2 parts of cold and 1 part of boiling water, the solution exhibiting a strongly acid reaction. It is much employed, in lieu of tartaric acid, for the production of carbonic acid, in ‘gazogenes,’ &c.; also to adulterate cream of tartar and tartaric acid. According to Dr Paris, it forms a “grateful adjunct to rhubarb.”—Dose, 12 gr. to 11⁄2 dr., in solution, combined with rhubarb or bitters, as the neutral sulphate.
Potassium, Sulphide of. Syn. Sulphuret of potassium, Liver of sulphur†; Potassii sulphuretum (Ph. L., E., & U. S.), Hepar sulphuris (Ph. D.), L. Prep. 1. (Ph. E.) Sulphur, 1 oz.; carbonate of potassium, 4 oz.; mix, heat them in a covered crucible till they form a uniform fused mass; when cold, break it into fragments, and preserve it in well-closed vessels. The formulæ of the Ph. L. 1836 and Ph. U. S. are similar.
2. (Ph. D.) Sublimed sulphur, 4 oz.; carbonate
of potassium (from pearlash, first dried, and then reduced to powder), 7 oz.; mix in a warm mortar, heat them in a Hessian crucible, as before, pour the fused mass into an iron cup, over which immediately invert a second vessel, to exclude the air, and, when cold, break the mass into fragments, and preserve it in a green-glass stoppered bottle.