TUNGSTEN. 255 



TUNGSTEN. 



The atomic weight of tungsten has heen determined from analyses or 

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

 barium. 



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

 gations. jNIalaguti* reduced this substance to the blue oxide, and from 

 the difference between tlie weiglits of tlie 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 that the trioxide 

 used be pure. 



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

 Berzelius.f 899 parts WC)3 gave, on reduction, 716 of metal. 676 of 

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

 WO3: 



^ 79.644, by reduction. 



79.905, by oxidation. 



Mean, 79.7745, =b .0S80 



These figures are far too high, the error being undoubtedl}' due to the 

 presence of alkaline impurity in the trioxide employed. 



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

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

 percentages of tungsten are as follows : 



Reductio7i Series. 

 79-336 

 79-254 

 79-312 

 79.326 

 79-350 



Mean, 79.3156 



Oxidation Series. 



79-329 

 79324 

 79-328 



Mean, 79.327 

 Mean of all, 79.320, =b .0068 



*Journ. fiir Prakt. Chem., 8, 179. 1836. 



tPoggend. Annalen, 8, i. 1825. 



I Journ. fi'ir Prakt. Cheni., 50, 152. 1S50. 



