306 Mr Graham on Water as a Constituent of Salts. 



Sulphate of zinc with saline water 



f Sulphate of zinc with sulphate of potash. 



Sulphate 01 zinc with saline water, \ f Sulphate ot zinc with sulphate of po 



Sulphate of water with sulphate > yields Sulphate of water with saline water 

 of potash, ) ( 



In the sulphate of zinc and potash, the whole six atoms of 

 water are retained with considerably greater force than in the 

 sulphate of zinc itself ; but even the double salt becomes anhy- 

 drous at 250°, and, indeed, the water retained falls below a single 

 atomic proportion, when the salt is dried in vacuo over sulphuric 

 acid, at a temperature not exceeding 78° Fahrenheit. The sul- 

 phate of potash in the double salt has not the effect of neutral- 

 izing the acid reaction of sulphate of zinc, according to my ob- 

 servations ; nor has it that effect in the case of any other double 

 salt. 



I subjoin a table of observations, made on the quantity of 

 water retained by this double salt, in different circumstances. 

 In the first two columns, the composition of the quantities ac- 

 tually examined is stated in grains. 





Anhydrous 

 Salt. 



Water. 



Anhydrous 

 Salt. 



Water. 



Dried in vacuo over sulphuric acid 1 

 for ten days, temp, from 68° to >- 

 78°, j 



Nine hours, at 238°, 



Two hours at 250°, and one hour "> 

 at 270°, . . . . / 



Four hours, at 250°, 



Composition of sulphate of zinc and ~1 

 potash with one atom water (by > 

 theory), ... ) 



17.2 



19.03 

 7.79 

 6.55 



0.68 



1.33 



0. 



0. 



100 



100 

 100 

 100 



100 



3.95 



6.99 



0. 



0. 



5.37 



Sulphate of Zinc with Sulphate of Soda : ZnS(NS)-|-H 4 . Sulphate 



of Zinc and Soda. 



This salt, I believe, has not hitherto been described. I fail- 

 ed in attempting to form it, by dissolving together sulphate of 



