VANADIUM. 183 



into SboOi, obtained a value approximately of Sb = 122. 

 Dumas, working with SbClj, obtained a similar value. 

 Schneider and Cooke, on the other hand, have established 

 an atomic weight for antimony near 120, and Cooke in par- 

 ticular has traced out the constant errors which lurked 

 unsuspected in the work of Dumas and Dexter. Now in 

 some physical respects tellurium and antimony are quite 

 similar. As constant errors vitiated the recently accepted 

 values for Sb, so they may also effect our estimates for Te. 

 The oxidation of Te by nitric acid resembles in minor par- 

 ticulars that of Sb. The analysis of K/reBre, gives a low 

 value for Te, and yet the material may have contained 

 traces of oxybromides, the presence of which would render 

 even that lower value too high. A careful revision of the 

 atomic weight of tellurium is still necessary. 



VANADIUM. 



Roscoe's determination of the atomic weight of vanadium 

 is the only one having any present value. The results ob- 

 tained by Berzelius * and by Czudnowicz f are unquestion- 

 ably too high ; the error being probably due to the presence 

 of phosphoric acid in the vanadic acid employed. This 

 particular impurity, as Roscoe has shown, prevents the 

 complete reduction of VoOg to V0O3 by means of hydrogen. 

 All vanadium ores contain small c^uantities of phosphorus, 

 which can only be detected with ammonium molybdate ; 

 a reaction unknown in Berzelius' time. Furthermore, the 

 complete purification of vanadic acid from all traces of 

 phosphoric acid is a matter of great difficulty, and probably 

 never was accomplished until Roscoe undertook his re- 

 searches. 



In his determination of the atomic weight, Roscoe t 



* Poggend. Annal., 22, 14. 1831. 



f Poggend. Annal., 120, 17. 1863. 



J Journ. Chem. Soc, 6, pp. 330 and 344. 1S68. 



