TARTARIC ACID. 117 



mic weight of the acid, while the composition 

 per cent, agrees very nearly with the results of 

 Berzelius. The agreement would be still nearer 

 were we to correct the data by which Berzelius 

 calculated the constituents : for the true weight 

 of the hydrogen which he obtained was not 

 3*807, but 3-641 per cent. A very slight trace 

 of water derived from some unknown source 

 would easily account for the slight surplus of 

 hydrogen. 



6. As the quantity of water in crystals of tar- 

 taric acid is accurately known, it occurred to me 

 that a more accurate idea might be formed of 

 the constituents of this acid, by analyzing the 

 crystals, than by any tartrate whatever. Accord- 

 ingly, a quantity of the acid was reduced to a 

 fine powder, and being placed between the folds 

 of a quantity of blotting paper, was subjected to 

 a considerable pressure for twenty-four hours, in 

 order to get rid of the hygrometrical water. 

 9'375 grains of this powder were triturated with 

 200 grains of peroxide of copper, and the mix- 

 ture being put into a copper tube, was exposed 

 to a red heat, under similar circumstances with 

 the oxalic acid, the analysis of which was related 

 in the preceding section. The weight of the 

 water obtained was almost exactly 3*375 grains,* 

 while the volume of carbonic acid was just 



* In some of my experiments the quantity of water extricated was 4-85 

 : but I "rive in the text the average of a number of trials. 

 H3 



