mate, 



OF MERCURY. 399 



loses no weight when heated on the sand bath, 

 it is anhydrous, and is composed of 



1 atom arsenic acid . 775 



1 atom protoxide of mercury 26 



33-75 



6. Protochromate of mercury. This is a fine Protochro- 

 red coloured insoluble powder, obtained by mix- 

 ing together solutions of protonitrate of mercury 

 and chromate of potash. 50 grains of this salt 

 dried in the open air, were digested in a solution 

 of caustic potash ; the protoxide of mercury was 

 separated in the state of a black powder, which, 

 dried in a gentle heat, weighed 38'57 grains. 

 The potash liquid assumed a yellow colour ; it 

 was neutralized by nitric acid, and mixed with 

 a solution of nitrate of lead till the whole chro- 

 mic acid was thrown down. The chromate of 

 lead dried on the sand bath weighed 31*57 

 grains, equivalent to 10*01 grains of chromic 

 acid. Thus it appears, that the constituents of 

 the salt are 



Chromic acid 10-01 or 6-5 



Protoxide of mercury 38-57 - 25-05 

 Water 1-42 - 0-922 



50-00 



The water being less than an atom, it is obvious 

 that the salt is anhydrous, and that the small 



