336 SALTS 



1 atom arsenic acid . 7 -75 



1 atom protoxide of nickel 4-25 

 6 atoms water 6*75 



18-75 



At the temperature of 500, it parts with 4 atoms 

 of water ; but retains 2 atoms. 



^' Binarseniate of nickel. When arsenic acid is 

 digested upon carbonate of nickel, no apparent 

 action is perceptible for some time ; but in a few 

 days the liquid acquires a fine green colour, and 

 the portion of carbonate of nickel which does not 

 dissolve assumes the peculiar shade of green 

 which characterizes the arseniate of nickel while 

 moist. When all action was at an end, the li- 

 quid was filtered, and gently evaporated to dry- 

 ness, on the sand bath. No crystals appeared ; 

 but a yellowish green matter was deposited, ra- 

 ther bulky, and having a good deal of clammi- 

 ness. To free it from adhering moisture, it was 

 placed between the folds of blotting paper, and 

 exposed for 24 hours to considerable pressure. 

 In this state it was insoluble in water, had a 

 slightly acid taste, and reddened vegetable blues 

 powerfully. It was, therefore, a binarseniate of 

 nickel. 50 grains of it, when exposed to a red 

 heat, became yellow, and lost 18*5 grains of its 

 weight ; but it still reddened vegetable blues as 

 powerfully as ever. From this experiment I 

 consider the salt as a compound of 



