274 WOLFRAM. 



v. Borch, 1851, Reduct, 7 Det., 313 212; 101. Mean 33 low. 



Oxidat, 2 Det., 359 339; 20. " 39 high. 



Dumas, 1860, Reduces Det., 389 259; 130. " 2 high. 

 Bernoulli, 1860, Impure materials. 



Persoz, 1864, Reduct, 2Det.,324 304; 20. u 4 high. 



Roscoe, 1872, Reduct, 3 Det., 308 1965112. " 47 low. 



Oxidat, 2 Det., 299 230; 69. u 45 low. 



Waddell, 1886, Reduct, 506^,362311 ; 51. " 29 high. 

 Pennington and Smith, 1894: 



Oxidat, 9 Det., 394 390; 4. " 82 high. 



Shinn, 1896, Oxidat, 4 06^,417377; 40. " 81 high. 



Schneider, 1896, Reduct, 3 Det., 323 307; 16. " 3 high. 



Oxidat, 3 Det., 314 304; 10. " o high. 

 Smith and Desi, 1894: 



Reduct, 6 Det., by weighing Ha O formed. 



The last method, introducing the questionable value of 

 hydrogen, must be excluded. Besides, it varies enormously 

 in different experiments for about the same amount of 

 material used. This series must be definitely thrown aside. 



There next remains the other two series made by and for 

 Professor Smith, giving 81 and 82 high, or 0.9 in atomic 

 weight, high. It would, standing by itself, give 185. It is 

 claimed that the material was specially free from Molybde- 

 num. 



Another fact is the extreme accuracy of weighing to the 

 thousandth of the milligramme! Where such a feature is 

 prominent, I have usually found serious errors in important 

 matters. Such spurious accuracy throws doubt on essential 

 points, at least in my mind. 



I have had no means of seeing the unreduced weighings. 

 The reduction to vacuum is claimed to have been made; 

 ho-Wy that is the great question. Compare what happened 

 in Smith's laboratory with the reductions of arsenic (see 

 p. 230). I fear that systematic errors lurk right here. 



The other determinations all agree reasonably well. 



Oxidation gives uniformly higher results than reduction, 

 except in the case of Roscoe, where reduction is abnormally 

 low. 



