286 VEGETABLE SUBSTANCES. 



chemical process to obtain the whole of the acid from 

 the tartar, some of which still remains combined with 

 the potash, forming a neutral salt. In the solution 

 of this neutral tartrate of potash, muriate of lime is 

 added, which immediately decomposes the salt, the 

 tartaric acid leaving the potash and combining with 

 the lime. The tartrate of lime thus obtained is washed 

 with abundance of water ; three-fifths of its weight of 

 strong sulphuric acid previously diluted with five parts 

 of water are then added, by which means the whole 

 of the tartaric acid is disengaged. Fourcroy pursued 

 another process to obtain the same result, and this, as 

 improved by Vauquelin, is considered a cheaper method. 

 A hundred parts by weight of tartar, to thirty of quick, 

 or forty of slaked lime, are mixed in boiling water. 

 A caustic magma is obtained, which is evaporated to 

 dryness by the application of a gentle heat. If this 

 be now digested in water, the potash in its caustic 

 state is alone dissolved, the whole of the tartaric acid 

 with which it Was combined having been taken up by 

 the lime, forming tartrate of lime, which is an inso- 

 luble salt : the acid may be obtained from this by the 

 equivalent quantity of sulphuric acid. Several other 

 methods are likewise employed for this purpose. One 

 of the simplest is to boil four parts of tartar in twenty 

 or twenty-four of water, and to add, gradually, one 

 part of sulphuric acid ; by continuing the boiling the 

 sulphuric acid will combine with the potash, and 

 forming sulphate of potash will precipitate, leaving 

 the acid free in the water. When the solution is re- 

 duced to about one-half by evaporation, it is filtered 

 and again boiled ; and if any more sulphate be depo- 

 sited, it must be again filtered. When entirely freed 

 from sulphate, the liquor is evaporated to a sirup. 

 Crystals of impure tartaric acid are formed in cooling, 

 which will be equal in quantity to half the weight of 



