200 SULPHURETS. 



(3.) Bisulphuret of copper. It is formed 

 when any of the salts of copper are precipitated 

 by a current of sulphuretted hydrogen gas. The 

 precipitate is at first brown, but becomes black 

 when dried. Its constituents are 



1 atom copper 4 



2 atoms sulphur 4 



Bismuth, 19. Sulphuret of bismuth. This compound 

 is easily formed by melting bismuth and sulphur 

 together in a close vessel. It exists native, and 

 is known by the name of bismuth glance. It has 

 a light lead grey colour, and the metallic lustre. 

 It occurs in small prismatic striated crystals, so 

 minute that their form has not been recognised. 

 It is much more difficult of fusion than bismuth. 

 Its constituents are 



1 atom bismuth . 9 



1 atom sulphur 2 



11 



20. Sulphuret of mercury. Two sulphurets 

 of mercury are known. The protosulphuret is 

 formed when a current of sulphuretted hydrogen 

 gas is passed through a solution of protonitrate 

 of mercury ; or still better, when the protoni- 

 trate of mercury is mixed with a solution of hy- 



