208 SULPHURETS. 



Klaproth, there are two sulphurets of tellurium. 

 The protosulphuret is steel grey, and has the 

 metallic lustre. When this sulphuret is fused 

 with an additional quantity of sulphur, a leaden 

 coloured sulphuret is formed, having a crystal- 

 line texture, and containing a maximum of sul- 

 phur. 



Arsenic, 34. Sulphuret of arsenic. There are two sul- 

 phurets of arsenic which have been long known, 

 and both of which occur in the mineral kingdom. 

 (1.) Protosulphuret of arsenic (realgar) is 

 formed when sulphur and metallic arsenic arc 

 heated together in close vessels, and the heat 

 continued till the excess of sulphur is driven off. 

 It is transparent, has a ruby red colour, and is a 

 compound of 



1 atom arsenic 4*75 

 1 atom sulphur 2 



6-75 



(2.) Sesquisulphuret of arsenic (orpiment) is 

 obtained when a solution of arsenic in muriatic 

 acid is precipitated by sulphuretted hydrogen : a 

 yellow powder falls, which is a compound of 



1 atom arsenic 4 -75 

 1^ atom sulphur 3 



7-75 



