TARTAR, in chemical technology, a name applied to crude acid potassium tartrate (bitartrate of potash) deposited in wine casks or vats during the process of vinous fermentation as a crys talline crust of "argol," containing about 75% of potassium bi tartrate. This argol when partly purified by recrystallisation is known as "tartar," and when further purified and freed from col ouring matter it becomes "cream of tartar." Cream of tartar is used medicinally as a diuretic and purgative.
The term "tartar" was formerly employed in a wider generic sense by the iatrochemists who included under this heading both the above tartarus vini and various substances obtained from it and even salts such as salt of sorrel (potassium oxalate) which resembled it. Thus sal fixurn tartari was dry potassium carbonate which on exposure to air deliquesced to oleum tartari per deli quium. Neutral potassium tartrate was termed tartarus tartarisa tus because it was prepared by neutralising ordinary tartar with the sal fixum Spiritus tartari employed by Paracelsus was prepared by dry distillation of tartar. This iatrochemist also used the term in a still wider sense to signify abnormal sediments deposited from animal secretions such as the concretionary masses separating in the liver, kidney or bladder, and usually referred to as "stone." Wine "Lees" and Argol.—Tartaric acid occurs in the juices of various fruits particularly the grape and tamarind. With the grape this acid passes into the expressed juice and during fermentation a deposit of sparingly soluble acid potassium tartrate is thrown down which forms the "lees" of wine. During the process of ma turing, a further quantity of this tartrate is precipitated and the deposit of "argol" constitutes the main source of commercial tar taric acid.
Cream of Tartar.—Granulated argol is dissolved to saturation in boiling water and the clear solution allowed to crystallise. The coloured crystals are redissolved in hot water and decolorised by means of pipeclay or egg albumen. On subsequent crystallisation, small, hard, colourless, transparent, rhombic prisms are obtained of cream of tartar. This salt dissolves in is parts of hot water but requires for solution 416 parts of water at o° C. It dissolves freely in solutions of boric acid or borax giving soluble cream of tartar, a white powder, permanent in air when made with boric acid but deliquescent when prepared with borax. Rochelle salt or potas sium sodium tartrate, KNa (C4H406), a purgative drug, is made by dissolving cream of tartar in aqueous sodium carbonate. On ignition cream of tartar evolves inflammable gases and leaves a residue of potassium carbonate and carbon.
Tartar Emetic (potassium antimonyl tartrate), K.(SbO)C4H406, 4H20, a long-known drug, being mentioned by Basil Valentine, is pre pared by warming 3 parts of antimony oxide or powder of algaroth (q.v.) with four parts of cream of tartar in presence of water. It separates from the filtered solution in colourless octa hedra which gradually lose their combined water, becoming opaque. It is soluble in 14.5 parts of cold and 1.9 parts of hot water. It has a nauseous metallic taste and produces vomiting when taken internally. In large doses it is poisonous. Besides its medicinal use it is employed as a mordant in dyeing and calico printing. (G. T. M.)