ATOMIC WEIGHTS 359 



TUI^GSTEN. 



The atomic weight of tungsten has been determined from analyses of 

 the trioxide, the hexchloride, and the tungstates of iron, silver, sodium 

 and barium. 



The composition of the trioxide has been the subject of many investi- 

 gations. Malaguti ' reduced this substance to the blue oxide, and from 

 the difference between the weights of the two compounds obtained a 

 result now known to be considerably too high. In general, however, the 

 method of investigation has been to reduce WO3 to W in a stream of 

 hydrogen at a white heat, and afterwards to reoxidize the metal, thus 

 getting from one sample of material two results for the percentage of 

 tungsten. This method is probably accurate, provided tluit the trioxide 

 used be pure. 



The first experiments which we need consider are, as usual, those of 

 Berzelius.^ 899 parts WO, gave, on reduction, 716 of metal. 676 of 

 metal, reoxidized, gave 846 WO3. Hence these percentages of W in 

 WO3: 



79.644, by reduction 

 79.905, by oxidation 



Mean, 79.7745, ± .0880 



Hence W = 189.324. . 



These figures are far too high, the error being probably due to the 

 presence of alkaline impurity in the trioxide employed. 



Next in order of time comes the work of Schneider,' who, with char- 

 acteristic carefulness, took every precaution to get pure material. His 

 percentages of tungsten are as follows : 



Reduction Series. 



79.336 



79.254 

 79.312 

 79.326 

 79.350 



Mean, 79.3156 



iJourn. prakt. Chem., 8, 179. 1S36. 

 2 Poggend. Annalen, 8, 1. 1826. 

 3Journ. prakt. Chem., 50, 152. 1850. 



