COMPOSITION OF OXIDE OF ZINC. 59 



So that 18*125 is the weight of an integrant 

 particle of the crystallized salt. It was the 

 knowledge of this that induced me to make 

 choice of 18*125 grains of the salt. My first 

 experiments were made upon a much larger 

 quantity ; but I have often repeated them with 

 18*125 grains, and obtained the result just 

 stated. 



If the solution of neutral sulphate of zinc be White vi - 



triol. 



concentrated too much, it deposites, while still 

 hot, an opaque crust upon the bottom of the 

 vessel. This crust is very white, not so soluble 

 in water as the crystals, and has not the least 

 appearance of crystallization. It is neutral, 

 though it reddens vegetable blues like the pre- 

 ceding salt; and being analysed in the same way 

 as the crystallized sulphate, was found composed 

 of 



1 atom sulphuric acid 5 

 1 atom oxide of zinc 5*25 

 3 atoms water . 3-375 



13-625 



So that an integrant particle of it weighs 13*625, 

 and it differs from the crystals in containing only 

 3 atoms of water, instead of seven. 



The white vitriol of the Germans consists of 

 this second salt, while the sulphate of zinc man- 

 ufactured in Great Britain consists of the for- 

 mer. The German white vitriol contains 24'77 



