TUNGSTEN. 63 



Protoxide of tungsten 100 



Oxygen . 7 



107 



Berzelius endeavoured to determine the quan- 

 tity of oxygen in tungstic acid by a very ingeni- 

 ous experiment, but rather of too complicated a 

 nature to be capable of perfect accuracy. He 

 formed a sulphuret of tungsten, by heating 1 part 

 of tungstic acid and 3 parts of cinnabar in a 

 Hessian crucible. The mixture was covered 

 with charcoal powder ; and the crucible, with a 

 flat lid on it, was exposed for half an hour to the 

 greatest heat which he could raise in a wind fur- 

 nace. The sulphuret thus obtained was a grey- 

 ish black-powder, which, when rubbed against a 

 polished surface, acquired the metallic lustre, 

 and resembled sulphuret of copper, but was ra- 

 ther more blue. 



100 parts of this sulphuret were digested in 

 nitromuriatic acid, till the sulphur was acidified. 

 The sulphuric acid was thrown down by muriate 

 of barytes ; and the sulphate of barytes formed 

 weighed 182 parts, equivalent to 24 '678 parts of 

 sulphur. Hence the sulphuret of tungsten is a 

 compound of 



Tungsten . 75-322 



Sulphur . 24-678 



100-000 



