64 URANIUM, ANTIMONY, CHROMIUM, &c. 



100 parts of the same sulphuret of tungsten, 

 heated in a platinum cup till it disengaged no 

 more sulphurous acid, left a brown powder, 

 weighing 93-5. This powder, being exposed 

 to a strong heat, became dark green, without 

 any alteration of its weight ; hence Berzelius 

 considered it as tungstic acid. 



From this experiment it follows, that tungstic 

 acid is composed of 



Tungsten 75-322 or 80-558 

 Oxygen 18-178 - 19-442 



93-500 100-000 



But 107 tungstic acid contains 100 protoxide of 

 tungsten and 7 oxygen ; or, its constituents may 

 be stated thus : 



Tungsten . 86-197 



Oxygen . 20-803 



107-000 



If from the 20-803 we subtract 7, there will re- 

 main 13*803 for the oxygen in 100 parts of pro- 

 toxide of tungsten. 



From this it appears, that the composition of 

 the oxides of tungsten is as follows : 



Protoxide 86-197 tungsten + 13-808 

 Tungstic acid 86-197 + 20-803 



But 13-803 : 20-803 : : 2 : 3 very nearly. Thus 



