TUNGSTEN. 147 



Dumas 79-312, ± .009 



Bernouilli, Reduction 79.413, ± .091 



" Oxidation 79-58i, dz .017 



Persoz 79-314. =fc -007 



Roscoe, Reduction 79.263, ±.023 



" Oxidation 79.2645, rb .0233 



General mean 79.3215, rfc .00085 



The rejection of the figures given by Berzelius and by- 

 Bernoulli exerts an unimportant influence upon the final 

 result. There is, therefore, no practical objection to retain- 

 ing them in the discussion. 



In 1861 Scheibler* deduced the atomic weight of tungsten 

 from analyses of barium metatungstate, BaO.4 WO3.9H2O. 

 In four experiments he estimated the barium as sulphate, 

 getting closely concordant results, which were, however, very 

 far too low. These, therefore, are rejected. But from the 

 percentage of water in the salt a very good result was 

 attained. The percentages of water are as follows : 



13-053 

 13-054 

 13-045 

 13.010 

 13.022 



Mean, 13.0368, ± .0060 



The work of Zettnow,t published in 1867, was somewhat 

 more complicated than any of the foregoing researches. He 

 prepared the pure tungstates of silver and of iron, and from 

 their composition determined the atomic weight of tungsten. 



In the case of the iron salt the method of working was 

 this: The pure, artificial FeW04 was fused with sodium 

 carbonate, the resulting sodium tungstate was extracted by 

 water, and the thoroughly washed, residual ferric oxide was 

 dissolved in hydrochloric acid. This solution was then re- 

 duced by zinc, and titrated for iron with potassium perman- 

 ganate. Corrections were applied for the drop in excess of 



* Journ. fiir Prakt. Chem., 83, 324. 

 f Poggend. Annal.. 130, 30. 



