SULPHURETS. 



drosulphtiret of potash. The precipitate is a 

 black powder, similar in appearance to protoxide 

 of mercury, but composed of 



1 atom mercury . 25 



1 atom sulphur . 2 



27 



The persulphuret of mercury is obtained when 

 a solution of corrosive sublimate is decomposed 

 by a current of sulphuretted hydrogen gas. The 

 precipitate is black, and bulky ; but when sub- 

 limed, it assumes a deep red colour, and be- 

 comes the pigment well known by the name of 

 cinnabar. It assumes a scarlet colour when re- 

 duced to powder ; and the colour becomes the 

 lighter the finer the powder is. The constituents 

 of cinnabar are 



1 atom mercury . 25 



2 atoms sulphur . 4 



29 



21. Sulphuret of silver. This compound is silver, 

 easily formed by heating sulphur and silver to- 

 gether. It has a lead grey colour, the metallic 

 lustre, possesses malleability and sectility, and 

 is much more easily fused than pure silver ; it 

 occurs native, and crystallized. The primary 

 form of the crystals is probably the cube. Its 

 constituents are 



