TUNGSTEN. 257 



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. 



79.55 6 

 79.526 



79-553 

 79.558 

 79-549 

 78.736 



Mean, 79.413 



Oxidation Series. 



79.55 

 79.656. 



79-555 

 79-554 



Mean, 79.581 

 Mean of all, 79.480, .056 



Two reduction experiments by Persozf give the following results : 



1-7999 S rm - WO 3 g av e 1.4274 g rm - w - 79-34 per cent. 



2.249 " 1-784 " 79.3 2 4 " 



Mean, 79.314, .007 



Next in order is the work done by Roscoe. J This chemist used a 

 porcelain boat and tube, and made six weighings, after successive reduc- 

 tions and oxidations, with the same sample of 7.884 grammes of trioxide. 

 These weighings give me the following five percentages, which,*for the 

 sake of uniformity with foregoing series, I have classified under the 

 usual, separate headings : 



Reduction Series. 



Mean, 79.263 



Oxidation Series. 

 79.230 

 79 299 



Mean, 79.2645 

 Mean of all, 79.264, .0146 



*Poggend. Annalen, in, 573. 1860. 

 t Zeit. Anal. Chem., 3, 260. 1864. 

 \ Ann. Chem. Pharm., 162,368. 1872. 



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