NICKEL. 359 



2. When 17-125 grains of crystallized sulphate 

 of nickel are exposed to a heat of 600 for half 

 an hour, they lose 6-25 grains of their weight, or 

 rather more than 5i atoms of water. But at this 

 temperature the salt does not lose its green 

 colour, and consequently, still retains water. 

 When 17-125 grains of the salt are exposed to a 

 low red heat, they lose their green colour, and in 

 general, diminish in weight 8 grains. But the 

 salt which has been thus treated, is not com- 

 pletely soluble in water, though very nearly so : 

 hence, a small portion of its acid has been dis- 

 engaged. From this experiment, which I have 

 often made, it appears that the water of crystalli- 

 zation in 17*125 grains of sulphate of nickel is not 

 quite so high as 8 grains. In one experiment in 

 which the heat was applied with much caution, 

 the loss of weight was 7*8 grains, and the salt 

 was completely soluble in water. It is obvious 

 from this, that the water of crystallization in 

 17-125 grains of sulphate of nickel lies between 

 7-8 and 8 grains. Now, 7-875 grains of water 

 are equivalent to 7 atoms of that liquid : and as 

 the quantity of acid in this weight of salt is just 

 5 grains, equivalent to an atom, we can have no 

 doubt that the true quantiy of water is likewise 

 equivalent to 7 atoms, or 7*875 grains. 



Five acid and 7-875 water, make 12-875, which ot j de 

 being subtracted from 17*125 leaves 4<25, which rf "*ei- 



must be the weight of protoxide of nickel, and 



z 4 



