1901.] SMITH AND EXNER — ATOMIC WEIGHT OF TUNGSTEN. 145 



Metallic Tungsten. 



It would be superfluous to set forth here the steps taken in pro- 

 curing the metaL They are familiar to every reader. They were 

 identical with those described by Hardin. One point, however, is 

 worthy of notice. It was discovered that if the trioxide, reduced to 

 metal, had been previously gotten by the ignition of ammonium 

 paratungstate in vessels of platinum, then it might well be expected 

 that after the removal of the tungsten from the reduction boats the 

 latter would show dark spots here and there. This occurred, but 

 uncontaminated trioxide was repeatedly reduced in porcelain by 

 hydrogen without leaving dark stains. 



Several experimenters — Riche, Desi, Shinn and Hardin — 

 endeavored to reach the atomic value of tungsten by collecting the 

 water resulting from the reduction of definite amounts of trioxide in 

 hydrogen. Their results were disappointing in the extreme, 

 although the method is surely rational and in some measure ideal. 

 The reasons for its failure have never been satisfactorily explained. 

 We were induced to give it trial. Every attention to detail was 

 scrupulously observed. The results were most disappointing, and 

 yet we cannot give a reasonable explanation for our failure. There 

 seems to be an inherent defect in the method which we were unable 

 to lay bare. 



We also reduced definite quantities of trioxide to metal, and 

 from the loss in weight sought to get the atomic value of tungsten. 

 Again the results were discordant. The boats were never stained 

 from the reduction, nor was the porcelain tube in which the 

 reduction took place stained, but on close scrutiny particles of 

 metal could be seen along the sides of the tube. They rested 

 loosely upon it and were removed with ease. This metal, in all 

 probability, was carried out into the tube by the aqueous vapor 

 produced in the reduction. This is, therefore, a serious point in 

 this method. 



There remained, finally, only method 2, another time-honored 

 method, upon which much discredit had been cast. Yet with pure 

 material it seemed worth the while to give it further trial. The 

 metal used in this study was made from trioxide obtained from the 

 hexachloride. Portions of it were weighed out into the same 

 crucibles which had been used in the experiments with the hexa- 

 chloride and gently heated with air contact. The steps in the 



PROC. AMER. PHILOS. SOC. XLIII. 170. J. PRIXTED JUNE 4, 1904. 



