Kali Præparatum, P.L. 1787. Sal Absinthii.
Sal Tartari. 1745.
Before the nature of this salt was well understood, it received various appellations according to the different methods by which it was procured, and it was supposed to possess as many different virtues, as Salt of Wormwood, Salt of Tartar, Salt of Bean Stalks, &c.
Qualities. Form, coarse white grains, so deliquescent, that by exposure to air they form a dense solution, (Oleum Tartari per deliquium, P.L. 1720.) Taste, alkaline and urinous.[[610]] Chemical Composition. This salt, although far from being pure, is sufficiently so for every pharmaceutical purpose. It consists of one proportional of acid and one proportional of potass, with variable quantities of sulphate of potass, muriate of potass, siliceous earth, alumina, together with the oxides of iron, and manganese. Solubility. It is dissolved by twice its weight of water; the residue, if any, may be considered as impurity; it is insoluble in alcohol; with oils it combines, and forms soaps. Incompatible Substances. They are enumerated under Potassæ Carbonas. Med. Uses. Antacid, and diuretic, (Form. 101, 107, 129), but it is far less pleasant than the carbonate; it is principally used for making saline draughts, see Acid. Citric. and Form. 107. Dose, grs. x to ʒss. Officinal Prep. Potassæ Acetas, L.E.D. (I) Liquor Potassæ L.E.D. (K) Potassæ Sulphuretum (I) L.E.D. Potassæ Tart. L.E.D. (I) Liquor Arsenicalis (I.L.) Adulterations. Its degree of purity may be estimated by the quantity of nitric acid, of a given density, requisite for the saturation of a given weight. The purest sub-carbonate is that obtained by incinerating cream of tartar, since most of the impurities are decomposed by the heat during the process, (Sub-carbonas Potassæ Purissimus. E.); it however generally contains lime.
POTASSÆ SULPHAS. L.E. Sulphas Kali. D.
Kali Vitriolatum, P.L. 1787.
Tartarum Vitriolatum, 1745, and 1720.
Sal de duobus, &c.
Qualities. Form, crystals which are right rectangular (but not square) prisms, modified on the edges and angles; or double six-sided pyramids with short intervening prisms, which are macles, or hemitrope crystals; they are slightly efflorescent, and when heated they decrepitate. Solubility. f℥j of water dissolves only grs. 24: the salt is insoluble in alcohol. Incompatible Substances. It is partially decomposed by the nitric and muriatic acids, in which case, a portion of the base being saturated, a corresponding portion of bi-sulphate results; this fact illustrates a chemical law of some importance, viz. that a substance less weakly attracted by another than a third, will sometimes precipitate this third from its combination with the second, in cases wherein a super, or sub-salt is readily formed.[[611]] The history of tartrate of potass will furnish farther illustrations. See page 183. Sulphate of potass, when in solution, is entirely decomposed by lime and its compounds; by oxy-muriate of mercury; nitrate of silver; and by acetate and sub-acetate of lead. Med. Uses. On account of its insolubility, it does not possess much activity as a purgative, but is said to be powerfully deobstruent; it should be exhibited in the form of powder, and in conjunction with rhubarb, or some other purgative medicine. Dose, grs. x to ℥ss. Form. 94. From its hardness and insolubility, it is a most eligible substance for triturating and dividing powders. Officinal Prep. Pulv. Ipecac. co. L.E.D. (M) Under the name Sulphas Potassæ cum Sulphure, the Edinburgh college retains the preparation formerly known by the name Sal Polycrest (Salt of many virtues); and as it is produced by deflagrating nitre with sulphur, the product, besides sulphate of potass, contains bi-sulphate and sulphuret of potass. It possesses no superiority over the common sulphate.
POTASSÆ SUPER-SULPHAS. L.