326 PROTOSALTS 



that their shape could not be ascertained ; the 

 greater number of them were nearly globular. 

 They were hard, not altered by exposure to the 

 air, and had an inky, though weak taste. 20 

 grains of these crystals, when exposed to as 

 strong a heat as they could bear without decom- 

 position, lost 3-8 grains. When the heat was 

 raised to about 600, the salt blackened, and lost 

 about 12 grains being exposed to a red heat, 

 the residuum was reduced to 6 -3 grains it was 

 sensibly magnetic. It was therefore drenched 

 with nitric acid, and exposed to a heat raised 

 gradually almost to redness. The weight of the 

 residue was now increased to 6*688 grains, equi- 

 valent to 6*012 grains of protoxide of iron, 

 and 6-012 : 4%5 : : 20 : 14-97- From this it is 

 obvious, that 15 grains of the salt contain just 

 4%5 grains of protoxide of iron. Consequently, 

 its constituents must be 



1 atom tartaric acid 8*25 



1 atom protoxide of iron 4-5 



2 atoms water 2-25 



15 



The preceding list is rather too scanty to per- 

 mit us to draw any inferences with respect to 

 the water of crystallization of the ferruginous 

 salts. 



