206 SULPHURETS. 



#9. Sulphuret of molybdenum. This sul- 

 phuret exists native, and is known by the name 

 of molybdena. It has a leaden colour, and is 

 composed of laminae, which are soft and flexible ; 

 and occasionally occur crystallized, in six-sided 

 prisms. It is a bisulphuret, and composed of 



1 atom molybdenum . 6 



2 atoms sulphur . 4 



10 



Tungsten, 39, Sulphuret of tungsten. I have made no 

 experiments on this compound. Berzelius in- 

 forms us, that tungsten combines with sulphur 

 in two proportions. He formed one of these 

 compounds by mixing cinnabar and tungstic 

 acid intimately together in a crucible, covering 

 the mixture with charcoal powder and a lid, and 

 then keeping the whole in a white heat for half 

 an hour. The sulphuret is a black powder, 

 which assumes the metallic lustre when rubbed 

 against a hard body. Berzelius says it contains 

 25 per cent, or 1th of its weight of sulphur. 

 Hence it was a bisulphuret, composed of 



1 atom tungsten . 15-75 



2 atoms sulphur . 4 



19-75 



When tungstic acid is dissolved in hydrosulphu- 

 ret of potash, and precipitated by an acid, a sul- 



