TARTRATE OF POTASH.

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and reduces vascular action. As a diuretic in dropsical complaints it isused in the same way. As & purgative it is not usually exhibited alone,but, in general, with jalap, sulphur, senna, or some other purgative.Thus, in dropsical complaints, a very valuable hydragogue cathartic is amixture of jalap and bitartrate of potash. In skin diseases and affectionsof the rectum (as piles, stricture, and prolapsus) a very useful purgativeis an electuary composed of sulphur, bitartrate of potash, and confectionof senna. An effervescing aperient may be prepared by mixing threedrachms of the bitartrate with two and a half drachms of carbonate ofsoda: the resulting salt is the potash-tartrate of soda. As a tooth-powder,bitartrate of potash is sometimes used on account of its gritty qualities :a very good dentrifice consists of equal parts of bitartrate, powderedrhatany root, and myrrh.

Administration. —As a hydragogue cathartic the dose is from four toeight drachms: as an aperient, one or two drachms: as a diuretic, inrepeated doses of a scruple to a drachm. Imperial (tisana imperialis ) isformed by adding boiling water to cream of tartar, and flavouring withlemon-peel and sugar. It may be taken, ad libitum, as a refrigerantdrink in febrile complaints. Cream of tartar whey (serum lactis tarta-rizatum) is made by adding about two drachms of bitartrate to a pint ofmilk. It may be diluted with warm water, and taken in dropsical com-plaints. The compound powder of jalap {pulvis jalapm compositus) of theLondon Pharmacopeia is composed of three ounces of jalap, six ouncesof the bitartrate, and two drachms of ginger : the dose is from a scrupleto a drachm in dropsical complaints.

Potas'sce Tar'tras. — Tar'trate of Pot'ash .

History. —This salt was known to Lemery. It has been termedtartarized tartar, tartarized kali, soluble tartar, or vegetable salt.

Preparation. —It is readily prepared by saturating the bitartrate withthe carbonate of potash. The proportions employed in the London Pharmacopoeia arc sixteen ounces (or as much as may be sufficient) ofcarbonate of potash dissolved' in six pints of boiling water, and threepounds of powdered bitartrate of potash. After boiling, strain, andevaporate until a pellicle forms ; then set aside to crystallize.

In this process the excess of acid in the bitartrate is saturated by thepotash of the carbonate : the carbonic acid escapes.

Properties. —It is usually met with in the shops in a granular state,but it ought to be crystallized. The primary form of the crystals is aright oblique-angled prism. To the taste this salt is saline, and some-what bitter. It deliquesces when exposed to the air, and is soluble inits own weight of water at 50° ; the solution decomposes by keeping.

Characteristics. —When heated to redness, it is decomposed, leavingas a residue charcoal and carbonate of potash. A solution of the tartrateproduces a white precipitate with solutions of acetate of lead, nitrate ofsilver, and chloride of calcium ; the precipitates being soluble in nitricacid. When heated, the salt evolves the odour of caromel. Tf an excessof any strong acid (as the sulphuric) be added to a solution of this salt,we obtain crystals of the bitartrate. Hence acids, and most aciduloussalts, are incompatible with it: as also are tamarinds. The tartrate is