TARTARIC ACID. (Fe., acide tartarigue ; GER., weinsaiire). Formula, Tartaric acid is another of the organic acids that occurs frequently in a natural state, especially iu the vegetable kingdom, not having been detected, we believe, in either the animal or mineral kingdoms. In a free state it occurs in the grape, pine-apple, tamarind, &c., with other acids in the mulberry, in sumach berries, in the needles of pine-trees, in sorrels and other sour-leaved plants, and in the roots of wheat, dandelion, and couch grass, as well as in the potato and so called Iceland moss. In combination with lime, it has been met with in madder root, squills, and quassia-wood.
Commercially, it seems to be derived solely from grapes, at different stages in the manufacture of wines. The following table shows the percentage, by weight, of this acid in the various wines went ioned Ben icarlo . 0545 Langlade .. 0510 Bergerac, White .. 0448 Madeira .. .. 0102 Bordeaux, ordinary .. .. 0390 Muscat Rivesaltes .. 0357 Bordeaux, Sauterne .. .. 0207 Narbonne 0606 Burgundy, Beaune .. '0477 Port Wine .. .. 0283 Burgundy, Pommard -0525 Rhine Wine .. .. 0480 Champagne .. 0408 Roussillon .. 0545 Cotes, White .. .. 0390 St. George .. .. 0414 Hermitage .. .. 0364 Tavella .. 0699 Lachrvma Christi .. .. 0336 Teneriffe 0351 But if these estimations he made by means of soda, some deduction must be allowed for the tannic acid, which, in the red wines more particularly, would tend to increase the percentage. Much the larger proportion of the acid occurs, however, combined with various bases, chiefly potash, and these tartrates of potash, obtained principally during the fermentation of the wine, are the most valuable of the salts present. Being but slightly soluble in a mixture of water and alcohol they are deposited in accordance with the generation of the alcohol, both in casks and in bottles, in the former case being known as argol and in the latter as crust. The deposit occurs as a hard crystalline crust, varying in quantity with the character of the grape, its degree of ripeness and the peculiarity of the treatment it has undergone for the production of wine. A ton of grapes will yield about 1 to 2 lb. of this deposit, which varies greatly iu composition. Scheurer-Kestner's
analyses of argols from Alsace, Burgundy, Hungary, Spain, Switzerland and Tuscany', show that the white contain from 67'30 (Hungary) to 88.50 (Tuscany) of bitartrate of potash, and from 1.6 (Alsace) to (Switzerland) of tartrate of lime ; while the red yield from 24.20 (Spain) to (Burgundy) of the former, and from 45.20 (Spain) to 46.25 (Burgundy) of the latter product.
The best argols come from Bordeaux, Marseilles, Montpelier, and Italy, but in quantities that do not equal the demand, and much of the tartar imported contains the tartrates of potash in minute crystalline powder, and often the biracemate replaces the bitartrate of potash, and the generally uncertain character and composition of crude tartars render tartaric acid making far less simple than it looks.
The ordinary process of manufacture adopted in this country is as follows :A large wooden vat of some 3000 to 4000 gallons capacity, called a generator, is provided with a series of revolving horizontal stirrers. This is about half filled with water, to which 40 cwt. of crude tartars are added ; then whiting or powdered chalk is carefully and gradually introduced to neutralize one equivalent of the tartaric acid of the bitartrate of potash, known by its creating no further efferves cence. It may be useful to state that 100 parts of pure bitartrate of potash require rather less than 24 parts of dry chalk. During the operation steam is forced into the vessel so as to maintain a temperature of 100°, and the stirrers are kept in constant motion to prevent the tartrate of lime from settling as a hard, dense mass. The solution will contain neutral tartrate of potash, which is decomposed by tho addition of sulphate of lime. Sulphate of lime is preferred generally to chloride as it costs nothing, and the sulphate of potash which it yields i.. more valuable than the chloride. A slight excess of gypsum is necessary beyond the theoretically required amount, as otherwise the reaction proceeds very slowly, and part of the potash tartrate is iu danger of escaping decomposition.