SULPHURETS. 193 



sulphuretted hydrogen gas is passed through a 

 neutral solution of nickel in an acid, the sul- 

 phuret of nickel also precipitates ; but the pre- 

 cipitation is prevented by adding an excess of 

 acid to the solution. The colour of the sulphu- 

 ret is yellowish grey ; it has the metallic lustre, 

 and is not brittle ; it is not attracted by the mag- 

 net. Its constituents are 



1 atom nickel . . 3-25 



1 atom sulphur . . 2 



5-25 



11. Sulphuret of cobalt. This sulphuret maycobait, 

 be formed either by heating metallic cobalt or 



its oxide with sulphur in close vessels. It pre- 

 cipitates when sulphuretted hydrogen gas is 

 passed through a solution of cobalt, provided 

 there be no excess of acid, which prevents the 

 precipitate from appearing. This sulphured has 

 a greyish yellow colour, a metallic lustre, and 

 appears crystallized ; it melts in a red heat. Its 

 constituents are 



1 atom cobalt . . 3-25 



1 atom sulphur . . 2 



5-25 



12. Sulphuret of manganese. This sulphuret Manga. 

 is easily obtained by heating the protosulphate of 

 manganese in a charcoal crucible. Prepared in 



this way, it has an iron grey colour, a semime- 



VOL. IT. N 



