BITARTRATE OF POTASH.

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Physiological Effects. —Two or three drachms cause purging, whichis sometimes accompanied with griping. In smaller doses, more especiallyif largely diluted, this salt acts as a mild diaphoretic. In its passage tothe kidneys it becomes decomposed, and converted into the carbonateof potash, which may be detected in the urine. Probably the pulmonaryexcretions of those who employ it also become impregnated with thissalt, since it has been said that in persons with delicate lungs it acts asan irritant to these organs.

Uses. —In this country it is rarely employed, except as a diuretic indropsical complaints. On the continent, however, it is administered invarious other diseases, as an alterative or resolvent, in scirrhus of thepylorus, chlorosis, and visceral and glandular enlargements. It maybe employed, in the lithic acid diathesis, to render the urine alka-line. It is of course exceedingly improper where phosphatic depositsare observed in the urine.

Administration. —It is given as a diuretic in doses of from a scrupleto a drachm and a half, dissolved in some mild diluent. In larger doses,as two or three drachms, it acts as a purgative.

Potas'see Bitar'tras. — Bitar'trate of Pot'ash .

History. —In its impure form, as a deposit from wine, it must havebeen known at a very early period. “ It is called tartar ,” says Paracel-sus , “ because it produces oil, water, tincture, and salt, which bum thepatient as hell does.” Scheele , in 1769, first explained its nature. Itssynonymes are cream of tartar, supertartrate of potash, and aciduloustartrate of potash. *

Natural History . —It is a constituent of many vegetables: thus it isfound in grapes, tamarinds, Cetraria islandica, &c.

Production. —All the bitartrate of commerce is obtained during thevinous fermentation. It exists in solution in grape juice ; but beingvery slightly soluble in a mixture of alcohol and water, it depositsduring fermentation (that is, when alcohol is produced), and forms acrust on the sides of the cask. In this state it is known in commerceunder the name of crude tartar (tartarus crudus ), or argol, and which istermed white or red (tartarus albus vel tartarus ruber), according as it isobtained from white or red wine.

Argol, or crude tartar, occurs in crystalline cakes of a reddish colour,and is composed of the bitartrate of potash, tartrate of lime (and some-times racemate of potash), colouring and extractive matter, &c.

At Montpelier, bitartrate of potash is procured thus:—Argol is boiledin water, and the solution allowed to cool, by which a deposit of crystalsis obtained; these are washed with cold water, and dissolved in boilingwater, containing charcoal and alumina (clay); the latter substances beingemployed to remove the colouring matter with which they precipitate.The clear liquor is allowed to cool slowly, by which crystals of thebitartrate are formed. These constitute the tartarus depuratus or crys-talli tartari of the older chemists. If a hot saturated solution of tartar becooled, the surface of the liquid becomes coated by a layer of very finecrystals of bitartrate : hence this crust was called cream of tartar (creatortartari.)

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