Foote and Langley — Tantalum and Columbixim. 401 



Art. XLIV. — Note on a Recent Method for Separating Tan- 

 talum and Columhuim I by H. W. Foote and R. W. 

 Langi-ey. 



A NEW method of separating tantalum from colurabium was 

 proposed recently by Weiss and Landecker.* This method 

 consists essentially in fusing the mixed oxides with sodium 

 carbonate containing a little nitrate and treating with hot 

 water. Some tantalum, as sodium tantalate, remains insoluble 

 and is removed by filtering and treated separately. The tan- 

 talum remaining in solution is precipitated by carbon dioxide. 

 The authors state that if the conditions are properly adjusted, 

 all the tantalum is precipitated, leaving columbium in solution. 

 On the other hand, Rosef and Ostwald:]: state that both 

 are completely precipitated by carbon dioxide from a sodium 

 carbonate solution. 



"We have tried a considerable number of experiments follow- 

 ing the directions given by Weiss and Landecker as closely as 

 possible but varying certain conditions not defined by the 

 authors. We were unable to make any satisfactory separation 

 by this method. On the contrary, in every case nearly all the 

 columbium precipitated with the tantalum. The authors state 

 that a separation depends upon adjusting the amounts of 

 reagents used, the method of fusion, and the concentration of 

 the solution within narrow limits. These conditions, in our 

 experiments, were adjusted to conform as closely as possible 

 with the slightly indefinite directions given by the authors. 

 The quantities of reagents and the concentration of solutions 

 were also varied somewhat to effect a separation if possible. 

 The method — taken from Weiss and Landecker — was as 

 follows. The amounts of reagents used will be given in the 

 table. About 0-3 gni. of a known mixture of tantalic and 

 columbic oxides was fused with sodium carbonate over a blast 

 till effervescence ceased. Sodium nitrate was added and the 

 fusion continued about ten seconds. The fusion was treated 

 with hot water on the steam bath for two hours and the 

 insoluble residue filtered and washed with 5 per cent sodium 

 bicarbonate solution. The filtrate, containing columbium and 

 tantalum, was cooled and carbon dioxide passed in until no 

 further precipitate formed. In the meantime, the insoluble 

 sodium tantalate was boiled with dilute sulphuric acid and 

 hydrogen dioxide to dissolve it. We were never successful in 

 getting complete solution at this point. Sulphurous acid was 

 added and the solution kept warm for two hours to reprecipi- 

 tate the dissolved tantalum. The precipitate was filtered, 



*Zeitscbr. anorg. Chera., Ixiv, 65, 1909. 

 •)■ Handbuch analyt. Chem., 6th ed., ii, 339. 

 i Grundlinien anorg. Chem., ed. 1900, 726. 



