TUNGSTEN. 127 



pared by gently heating the ammonium salt in a muffle. 

 {Ajinal. de Chim. etde Plu/s., (3,) 55, 1859, 144.) 



F. A. Bernoulli : 186.8 (O = 16) ; 1167.5 (0 = 

 100). 



Bernoulli made five experiments on the reduction of 

 tungstic acid by hydrogen in a porcelain tube at a very 

 high temperature, two experiments on the amount of water 

 formed in reduction, and four experiments on the oxidation 

 of tungsten. The mean result was W = 93.41 ; extreme 

 difference, 0.75. [If experiment 9, in which oxidation 

 seems to have taken place, is left out, the mean becomes 

 93.35; extreme difference, 0.18.] The tungstic acid was 

 prepared from ammonium tungstate which had been boiled 

 for several days with nitric acid. The tungstic acid was 

 heated to redness. One part of it was green, another part 

 yellow. The determinations from the different colored 

 acids did not differ, and Bernoulli considers them isomeric 

 modifications of the same compound. There appear to be 

 misprints in the data given. [Poggend. Ann., Ill, 1860, 

 599.) 



0. SCHEIBLER : 184 (O = 16). 



Scheibler reached this value by five determinations of 

 the water contents (9 molecules) of barium metatungstate. 

 From determinations of the barium and the tungsten in 

 the same compound Scheibler reached other values, but he 

 regards the water determination as the most trustworthy. 

 {JErdm-ann's Juurn. fiir Prak. Chem., S3, 1861, 328.) 



E. Zettnow: 183.952 (0 = 16). 



Determined from analyses of ferrous tungstate and 

 argentic tungstate. A known weight of ferrous tungstate 

 was melted with sodium carbonate and the mass dissolved. 

 The ferric hydrate was thoroughly washed, dissolved in 

 chlorhydric acid, reduced to ferrous chloride with zinc of 

 known composition, and titrated with potassic permanga- 

 nate in several measured portions. Four such series of 

 experiments were made, and gave a mean of 92.038 for W ; 

 extreme difference, 0.33. The ferrous tungstate was pre- 

 pared by melting pure anhydrous sodium tungstate with 

 ferrous chloride and sodium chloride, dissolving, separat- 

 ing impurities, crystallizing, washing the crystals with 

 water, chlorhydric acid and sodium carbonate. The argen- 



