340 SALTS 



Hence, there can be no doubt that the salt is a 

 compound of 



1 atom oxalic acid 4*5 



1 atom protoxide of nickel 4'25 

 ' 4 atoms water 4' 5 



13-25 



The 0-322 of surplus water found by experi- 

 ment, was no doubt lodged mechanically in the 

 powder. It is scarcely possible to avoid such 

 slight excesses of water, when we examine a 

 salt which forms only a powder, because there 

 is no criterion by which we can know when all 

 the hygrometrical water is driven off; and in 

 many cases it would be hazardous to attempt to 

 drive it off by heat. On the sand bath the salt 

 loses very nearly, but not quite, an atom of wa- 

 ter: for 13-25 grains would have lost 1-09975 

 grains. Probably, had the heat been continued 

 long enough, the loss would have amounted to 

 exactly an atom, leaving 3 atoms of water still 

 united to the salt. 



Tartrate. 10. Taitrate of nickel. This salt was formed 

 by dissolving carbonate of nickel in tartaric 

 acid ; a green solution was obtained, which, 

 when evaporated to dryness, left a light olive 

 green powder, which was tasteless, insoluble in 

 water, and producing no alteration on vegetable 

 blues. It was anhydrous, for 12-88 grains, when 

 exposed to the strongest heat which it could 



