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ELEMENTS OF MATERIA MEDICA.
three or four grains gradually increased. It may be given either in solu-tion or in the form of pill made with soap. For external use it isemployed in solution in water, as already described, or in the form of !ointment, composed of half a drachm of the sulphuret to an ounce of lard.
Antidotes. —In the event of poisoning by this substance the antidoteis a solution of chloride of soda or of chloride of lime.
History and Synonymes.— The mode of preparing this salt wastaught by Lowitz and Link at the latter end of the last century. The salthas had various names, such as supersulphate of potash, sal enixum, acid,vitriolated tartar , and sal auri philosophicum.
Preparation.— It is ordered to be prepared by dissolving two poundsof the salt left after the distillation of nitric acid in four pints of boilingwater, then adding one pound of sulphuric acid to it, boiling down themixture, and setting aside to crystallize. It is also a product of variousother manufactures.
Properties. —It is crystallizable, the primary form of the crystal beingeither a right rhombic prism, or the right rhombic octahedron. It has avery acid taste, and reacts strongly as an acid on vegetable colours, anddecomposes the carbonates with effervescence. It is soluble in abouttwice its weight of water at 60°. By a red heat it evolves sulphuric acid, .and is converted into the neutral sulphate of potash. I
Composition. —It consists of— j
Eq. Eq.Wt. Per Cent. Geiger.
Sulphuric Acid. 2 ... . 80 ... . 54*80 .... 54*77
Potash. 1 . . . . 48 ... . 32*87 .... 32*53
Water.2 . . . . 18 ... . 12*33 .... 12*70
Crystallized Bisulphate Potash . . 1 . . . . 146 .... 100*00 .... 100*00
Characteristics. —The presence of sulphuric acid may be recognizedby the chloride of barium ; while the potash may be detected by thecharacters already mentioned for this substance. From the neutral sul-phate of potash it is distinguished by its acid taste, its action on litmusand the alkaline carbonates, and by its greater solubility.
Physiological Effects and Uses. —It is rarely used as a medicine.
It possesses the combined properties of sulphuric acid and sulphate ofpotash. The excess of acid renders its local operation that of an astrin-gent. When swallowed, it operates as a mild purgative, and may beemployed in the same cases as the sulphate, over which it has the advan-tage of greater solubility. Conjoined with rhubarb it covers the bittertaste of the latter without injuring its medicinal properties. Dr. Barker{Observations on the Dublin Pharmacopoeia, p. 138) says it may be used to ''form a cheap effervescing purgative salt, as follows :—73 grains of bisul-phate of potash and 72 grains of crystallized carbonate of soda, to be 'separately dissolved in two ounces of water, and taken in a state of !effervescence.
Administration. —The dose of it is from gr. x. to 3ij. properly jdiluted.
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