Pennington and Smith.] 06± [Nov. 2, 



(Braua, Zeit.f. Analyt. Chemie, 2, 36) for molybdenum applied to its aqueous 

 solution. The presence of molybdenum was very evident. The ignition 

 of the tungsten trioxide in the earlier stages of purification had not elimi- 

 nated this constituent. Instead of adopting Rose's method as was done 

 by "Waddell, and thus introducing the possible contamination from a fixed 

 allvali, recourse was had to the reaction of Debray — the volatilization of 

 themolybdicacidasoxychloride — M0O3. 2HC1 {Compt. rend., 46, 1098, and 

 Liebig's Annalen, lOS, 250). The experiments of Pechard {Compt. rend., 

 114, 173, and Zeit.f. anorg. Chemie, 1, 262), as well as those more recently 

 made by Smith and Oberholtzer {Journ. Am. Chem. Soc, 15, 18, and Zeit. 

 f. anorg. Chemie, 4, 236), and by Smith and Maas {Journ. Am. Soc, 15, 

 397, and Zeit.f. anorg. Chemie, 5, 280), give evidence that by this means 

 molybdenum can be expelled from tungsten derivatives. To this end the 

 remainder of the tungsten trioxide was placed, in portions, in a porcelain 

 boat and exposed to the action of hydrochloric acid gas, aided by a gentle 

 heat (150-200O C), until a volatile sublimate of M0O3. 2HC1 was no 

 longer noticed. Upon reoxidizing the residual tungsten trioxide in opeu 

 porcelain crucibles and then subjecting portions of the same to the sul- 

 phocyanide test the presence of molybdic acid was no longer observed. 

 This was taken as an evidence ot its complete removal. 



The trioxide subjected to the treatment described in the last paragraph 

 was suspended in water into which ammonia gas was conducted. The 

 oxide dissolved without leaving a trace of foreign matter. The salt ob- 

 tained upon evaporation was crystallized three times ; it was then dried 

 and ignited with careful exclusion of dust. This material was now re- 

 garded as sufficiently pure for the experiments projected. As it was not 

 intended to attempt any determinations by reduction of the oxide, the 

 latter was reduced in a current of hydrogen, carefully purified, to the 

 metallic state. The reductions were made in a large platinum crucible 

 after the manner of Von Pfordten {Ber. d. deutsch. Chem. GeselL, 17, 731). 

 Inasmuch as the reduced metal slowly alloys with the platinum the resulting 

 metallic powder was in all instances gently shaken from the crucible after 

 it had cooled in a current of hydrogen. The reduction of trioxide pro- 

 ceeds quite rapidly in the above manner and is always complete. The 

 product is dark gray in color. Its specific gravity was found to be 18.64 

 at 0°. It was carefully preserved from dust and moisture in drying 

 bottles. 



The amount of oxygen absorbed by the conversion of tungsten into its 

 trioxide was made the basis of the determinations recorded in this paper. 



The oxidations were made in porcelain crucibles. These were sup- 

 ported in close-fitting asbestos rings so that reducing gases could not gain 

 access to the hot oxide. To avoid loss from particles being carried out 

 mechanically a porcelain lid wider than the crucible was placed over it, 

 at the height of one half inch. A careful examination of this lid from 

 lime to time showed no traces of tungstic oxide. Dust particles were 

 also excluded in this manner. No other work was done in the room in 



