306
ELEMENTS OF MATERIA MEDICA.
Properties. —As met with in commerce, this salt forms a white crys-talline mass, without odour, but having an acidulous and gritty taste.The primary form of the crystals is a right rhombic prism. It is unal-tered by exposure to the air; but when heated, it decomposes, swellsup, evolves various volatile products, gives out an odour of caromel,and is converted into black flux (fluor niger ), —a compound of charcoaland carbonate of potash. If the bitartrate be deflagrated with nitrateof potash, the residue is white flux (fluor albus ), or carbonate of potash, iBitartrate of potash is very slightly soluble in water, and is insoluble in .alcohol.
Characteristics. —One character of this salt is derived from the phe-nomena attending its conversion into black flux, as above mentioned. If ■black flux be digested in water we obtain a solution of carbonate ofpotash, known by the properties before mentioned (p. 301.) Anothercharacter of the bitartrate is its slight solubility in water, and the jsolution reddening litmus. The addition of caustic potash increases itssolubility, whereas alcohol diminishes it. Acetate of lead added to a solu- <tion of the bitartrate forms a copious white precipitate ; lime water has |the same effect. Mixed with alkaline carbonates it produces effervescence.Boracic acid, or borax, very much increases the solubility of this saltin water, forming what has been termed soluble cream of tartar (cremortartari solubilis), or tartarus boraxatus of some writers.
Composition. —Crystallized bitartrate of potash has the followingcomposition :—
Potash. 1 . . . . 48 ... . 25-3 .... 24'80
Tartaric Acid.2 . . . . 132 .... 70‘0 .... 70’45
Water. 1 . . . . 9 . . . . 47 ... . 475
CrystaUizedBitariLPotash. 1 .... 189 ... . lOO'O . . . ■ lOO’OO
Impurity. —Bitartrate of potash usually contains from 2 to 5 per cent,of tartrate of lime, and hence a little carbonate of lime may be detected inblack flux. This is of no material consequence in a medicinal point ofview If the powdered bitartrate be adulterated with either alum or jbisulphate of potash, the fraud may be detected by chloride of barium, |!which causes a white precipitate (sulphate of baryta) insoluble in nitricacid.
Physiological Effects. —When taken in small doses, diluted withwater, it acts as a refrigerant and diuretic : in larger doses (as two orthree drachms) it purges, and frequently creates flatulence and griping.By continued use it disorders the digestive functions, and causes ema-ciation, most probably from defective nutrition. In excessive dosesit produces inflammation of the stomach and intestines. A fatal case hasbeen recorded by Mr. Tyson {Med. Gaz. vol. xxi. p. 177.) A man, to jrelieve the effects of drunkenness, swallowed four or five table-spoonfuls jof cream of tartar. It caused violent vomiting and purging, and other !symptoms of gastro-enteritis, and pain in the loins. The thighs and legs iappeared paralyzed. He died on the third day. On a post-mortemexamination the stomach and intestines were found inflamed. j
Uses. —Bitartrate of potash is frequently employed in the form ofimperial or cream of tartar whey, as a refrigerant drink in febrile andinflammatory diseases. It allays thirst, diminishes preternatural heat,