OF ALUMINA. 317 



10. Tartrate of alumina. Tartaric acid dis- 

 solves hydrate of alumina with facility. The sa- 

 turated solution has an acid, astringent, and 

 sweet taste. Being evaporated to dryness, the 

 tartrate assumed the form of a white semitrans- 

 parent viscid mass, having a slight shade of yel- 

 low, and very like gum-arabic in appearance. 

 On exposure to the air, it became brittle ; but 

 still continued to redden vegetable blues. 



1 1*625 grains of this salt, when kept for half an 

 hour in a red heat, left 2-25 grains of alumina. 

 I found, by another experiment, that the acid 

 contained in 11-625 grains of this salt just satu- 

 rate 4 grains of pure soda. Hence, the consti- 

 tuents of the salt are 



1 atom tartaric acid 8-25 



1 atom alumina . 2'25 

 1 atom water . 1*125 



11-625 



If any consequences can be drawn from the pre- 

 ceding list of aluminous salts, they seem all to 

 contain water of crystallization, though the num- 

 ber of atoms is very various. Two of the salts 

 contain only 1 atom of water two contain 3 

 two 6 one contains 7 and one 10. 



