ATOMIC WEIGHTS 



361 



Dumas ' gives only a reduction series, based upon trioxide obtained 

 by the ignition of a pure ammonium tungstate. The reduction was effected 

 in a porcelain boat, platinum being objectionable on account of the ten- 

 dency of tungsten to alloy with it. Dumas publishes only weighings, 

 from which I have calculated the percentages: 



2.784 grm. WO3 gave 2.208 grm. W. 79.310 per cent. 



79.259 

 79.326 

 79.289 

 79.280 

 79.389 

 79.324 

 79.317 



Mean, 79.312, ± .009 

 Hence W= 184.019. 



The data furnished by Bernoulli ' differ widely from those just given. 

 This chemist undoubtedly worked with impure material, the trioxide 

 having a greenish tinge. Hence the results are too high. These are the 

 percentages of W : 



Reduction Series. 

 79.556 

 79.526 

 79.553 

 79.558 

 79.549 

 78.736 



Mean, 79.413 



Oxidation Series. 

 79.558 

 79.656 

 79.555 

 79.554 



Mean, 79.581 

 Mean of all, 79.480, ± .056 



Hence W = 185.918. 



Two reduction experiments by Persoz ^ give the following results 



1.7999 grm. WO3 gave 1.4274 grm. W 

 2.249 " 1.784 



79.304 per cent. 

 79.324 



Mean, 79.314, ± .007 



Hence W=: 184.041. 



Ann. Chem. Pharm., 113, 23. 1S60. 



■ Poggend. Annalen, 111, 573. 1860. 



■ Zeit. anal. Chem., 3, 260. 1864. 



