TARTARIC ACID 971 



specific gravity of r9o3, dissolves in 16 parts of boiling water, and in 200 parts 

 at 60 Fahr. It is insoluble in alcohol. It consists of 24'956 potash, 70-276 tartaric 

 acid, and 4768 water. See ARGOL ; POTASH, BITAHTKATE OF. 

 TARTAR, CREAM OF. Acid tartrate of potash. 



TARTAR EMETIC. Tartrate of potash and antimony, prepared by boiling 

 teroxide of antimony in solution of cream of tartar. 



TARTARZC ACID, (Acide tartrique, Fr. ; Weinsteinsaure, Ger.) This is pre- 

 pared by adding gradually to a boiling-hot solution of 100 parts of tartar (bitartrate 

 of potash') in a large copper boiler, 26 parts of chalk (carbonate of lime) made into a 

 smooth pap with water. A brisk effervescence ensues, from the disengagement of the 

 carbonic acid of the chalk, while its base combines with the acid excess in the tartar, 

 and forms an insoluble precipitate of tartrate of lime. The supernatant liquor, which 

 is a solution of neutral tartrate of potash, must be drawn off by a syphon, and decom- 

 posed by a solution of chloride of calcium (muriate of lime). 28 parts of the dry 

 chloride are sufficient for 100 of tartar. The tartrate of lime, from both processes, 

 is to be washed with water, drained, and then subjected in a leaden cistern to the ac- 

 tion of 49 parts of sulphuric acid, previously diluted with 8 times its weight of water : 

 100 of dry tartrate take 75 of oil of vitriol. This mixture, after digestion for a few 

 days, is converted into sulphate of lime and tartaric acid. The latter is to be sepa- 

 rated from the former by decantation, nitration through canvas, and elutriation of 

 the sulphate of lime upon the filter. 



The clear acid is to be concentrated in leaden pans by a moderate heat, till it 

 acquires the density of 40 B. (sp. gr. 1'38), and then it is run off, clear from any 

 sediment, into leaden or stoneware vessels, which are set in a dry stove-room for it to 

 crystallise. The crystals, being re-dissolved and re-crystallised, become colourless 

 six- sided prisms. In decomposing the tartrate of lime, a very slight excess of sul- 

 phuric acid must be employed, because pure tartaric acid would dissolve any tartrate 

 of lime that may escape decomposition. Bone-black, previouslyfreed from its carbon- 

 ate and phosphate of lime, by muriatic acid, is sometimes employed to bleach the 

 coloured solutions of the first crystals. Tartaric acid contains nearly 9 per cent, of 

 combined water. It is soluble in two parts of water at 60, and in its own weight of 

 boiling water. In its dry state, as it exists in the tartrate of lime or lead it consists 

 of 36-8 of carbon, 3 of hydrogen, and 60'2 of oxygen. It is much employed in 

 calico-printing, and for making sodaic powders. 



In consequence of the great variation in the constituents of argol or rough tartar, 

 the manufacture of tartaric acid is not nearly so simple as a first glance at its several 

 processes might lead an inexperienced individual to suppose. The theory of preparing 

 tartaric acid seems, indeed, a remarkably easy affair ; and provided the materials operated 

 upon were pure, or of uniform quality, no kind of manufacture could put on less the 

 appearance of risk or speculation. But too many know, to their cost, with what ready 

 facility the whole profit, and something more, of a large operation will occasionally 

 ooze off through a variety of unknown channels, and present a sadly defective and 

 truncated return of saleable produce. In fact, money is not unfrequently lost in this 

 manufacture by very old and experienced makers. The differences in argol arise 

 from the greater or smaller amount of tartrate of lime combined with the bitartrate 

 of potash ; these differences will, in a commercial way, amount to from 5 to 25 or even 

 30 per cent. ; and herein resides a difficulty requiring more analytical skill and 

 chemical knowledge than is commonly found amongst practical manufacturers. We 

 will suppose that an argol has been purchased, containing by analysis 70 per cent, of 

 bitartrate of potash, but also, though unknown to the purchaser, containing 20 per 

 cent, of tartrate of lime. According to the process followed, this argol would be 

 dosed with a definite proportion of chalk or carbonate of lime, so as to produce 

 tartrate of lime with the extra tartaric acid of the supertartrate of potash. This 

 tartrate of lime, being insoluble, would fall and mingle with the 20 per cent, already 

 existing ; but as in practice the quantity of sulphuric acid employed for subsequent 

 decomposition of this tartrate of lime is proportioned to the amount of chalk 

 originally employed, it follows that the tartrate of lime naturally present in the argol 

 is left undecomposed, and comes to be regarded as sulphate of lime, to the great loss 

 of the manufacturer, who probably finds his more intelligent neighbour able to buy 

 as he buys, and yet capable of underselling him in the open market. 



The composition of crystallised tartaric acid, appears to be represented bv the 

 formula C^O 12 (C 4 HO 6 ). By the action of heat it loses 2HO (H 2 O), and becomes 

 anljydrous tartaric acid. Various metamorphoses have been stated to occur in tartaric 

 acid upon exposing it to heat. Laurent, Gerhardt, and Pasteur have investigated this 

 matter, and have given the names of metatartaric acid and isotartaric acid to two of 

 the results. Another acid has been investigated by Arppe, the pyrotartaric acid. 

 According to Mi lion and Reiset, the best mode of preparing it is to distil powdered 



