OF MERCURY. 395 



19- SALTS OF MERCURY. 



Both of the oxides of mercury combine with 

 acids and form salts, several of which are capa- 

 ble of crystallizing. 



(1.) PROTOSALTS. 



1. Protosulphate of mercury. This salt is 

 formed when sulphuric acid is heated on mer- 

 cury. Sulphurous acid exhales, and protosul- 

 phate of mercury is gradually deposited in fine 

 white crystals. When these crystals are washed 

 with a little water they may be dried on blotting 

 paper ; in this state they constitute a white salt 

 in scales. It has very little taste, reddens vege- 

 table blues, and when heated on the sand bath 

 the colour becomes darker, the salt assumes a 

 silky lustre, and the scaly structure is much 

 more conspicuous. 32-725 grains heated on the 

 sand bath lost 1*7&5 grain. Probably the con- 

 stituents are 



1 atom sulphuric acid . 5 



1 atom protoxide of mercury 26 



2 atoms water . . . 2-25 



33-25 



2. Nitrate of mercury. This salt is easily ob- Nitrate, 

 tained by dissolving in nitric acid of the specific 

 gravity 1*42, as much mercury as it will take 



