SULPHATE OF POTASH.

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Potass(B Sul'phas.—Sulphate of Pot'ash .

History and Synonym es. —The mode of preparing this salt was taughtby Oswald Croll in 1643. It has been known by various appellations,such as specificum purgans Paracelsi, Arcanum duplicatum, vitriolatedkali, vilriolated tartar, sal poly chrest (literally signifying salt of many usesor virtues), sal de duobus, &c.

Natural History . —Sulphate of potash is found in both kingdoms ofnature.

(a.) In the inorganized kingdom .— It has been met with in small quan-tities in some mineral waters of Saxony and Bohemia , in native alum,in alum-stone, and in a mineral called polylialite, in which Stromeyerfound no less than 27'6 per cent, of the sulphate of potash.

(h.) In the organized kingdom .— It has been found in the root of Poly-gala Senega, Winter’s bark, the bulb of garlic, myrrh, opium, &c. Theblood and urine of man also contain it.

Preparation. —It is obtained from the residuum of the distillation ofnitric acid, either by igniting it in a crucible to expel the excess ofsulphuric acid, as directed in the Pharmacopoeia , or by saturating it withcarbonate of potash.

Properties. —It crystallizes in single or double six-sided pyramids,the primary form of which is the right rhombic prism. It is hard,inodorous, has a saline bitter taste, and is unchanged by exposure to theair. When heated it decrepitates. At 60° F. it requires sixteen timesits weight of water to dissolve it: it is insoluble in alcohol. It is decom-posed by tartaric acid, which forms with it crystals of bitartrate of potash.

Composition. —The crystals contain no water of crystallization. Theyare thus composed :—

Eq. Eq.Wt. Per Cent. Wenzel.

Sulphuric Acid .... 1 .... 40 ... . 4.V45 .... 45'25

Potash. 1 .... 48 ... . 54-55 .... 54*75

Sulphate of Potash . . 1 .... 88 ... . 100*00 .... lOO’OO

Characteristics. —I have already mentioned these, when describingthe bisulphate.

Physiological Effects. —It acts as a very mild purgative, withoutoccasioning any heat, pain, or other symptoms of irritation. Its opera-tion is, in fact, too mild for ordinary use.

Uses. —It is particularly serviceable as a laxative in disordered condi-tions of the alimentary canal, as diarrhoea and dyspepsia, in hepaticdisorders, and in lisemorrlioidal affections. It is best given in combina-tion with rhubarb. Thus, from five to ten grains of rhubarb, with fromfifteen grains to two drachms of this salt, will be found to act mildly andefficiently in many cases of dyspepsia and diarrhoea. It is an excellentaperient for children. The objections to its employment are its slightsolubility, and that when given in large doses to children it is apt toproduce vomiting. It is useful, on account of its hardness, for trituratingand dividing powders, as in the pulvis ipecacuanhce compositus.

Dose.—I t is given in doses of from fifteen grains to four or fivedrachms.