402 



Tantalum, and Colunih/uni. 



washed, ignited and wei<2:hcd. The oxide preci])itated with 

 earhou dioxide, whicli should liave been pure taiitalic oxide, 

 was tiUored and tlie wei<>;ht after ignition added to the weight 

 of tantalie oxide already ol)tained. 



The tiltrate from the carbon dioxide precipitation was acidi- 

 fied with sulphuric acid, an excess of sulphurous acid added, 

 the solution boiled and allowed to stand. The precipitate 

 which should have contained all the colund)iuni was filtered, 

 Avashed, ignited and weighed. As a precaution ammonia was 

 added to the filtrate to be sure that no colunibium was left in 

 solution. 



The results of these experiments are tabulated below. They 

 show that we obtained no separation in any case, but that 

 columbium was almost quantitatively precipitated with the 

 tantalum by carbon dioxide. The precipitate must have 

 carried some alkali with it as the amount of tantalum and 

 colnmbium oxides recovered was always apparently greater 

 than the amount used. 



The results of the experiments are tabulated below. 













Na.COs 



KaNOs 



Vol- 

 ume 

 when 







TaaOe 



CbjOe 



Ta^Oe 



Cb^Os 



used 



used 



COc, 



Eemarks. 



taken 



taken 



found 



found 



for 



for 



was 













fusion 



fusion 



passed 







(gms) 



(gms) 



(gms) 



(gms) 



(gms) 



(gms) 



(cc) 















about 



about 







1. 



•2100 



•0900 



•3025 



none 



2 gms. 



1 gm. 



600 





2. 



•2129 



•0913 



•3219 



•0117 



•58 



•05 



250 





3. 



•1975 



•0846 



•2903 



•0125 



1-2 



•05 



250 



A precipitate separ- 

 ated on standing 

 over night before 

 passing CO^. 



4. 



•2465 



•0616 



•3167 



•0030 



•6 



•05 



250 



Precipitate with CO, 

 separated in 1 hour 

 stopped CO2 in li^ 

 hours. 



5. 



•2362 



•0591 



•2974 



•0056 



1-2 



•05 



250 





6. 



•2580 



•0645 



•3193 



•0167 



V8 



•05 



250 





7. 



•2546 



•0637 



•3220 



•0087 



rs 



•05 



250 



Fused mass when 

 treated with water 

 contained many 

 crystalline plates. 



8. 



•2728 



•0682 



•3425 



•0037 



1-8 



01 



250 





9. 



•2838 



■0710 



•3654 



trace 



r8 



0^1 



250 



Precipitate with car- 

 bon dioxide became 

 crystalline on boil- 

 ing. 



The results have convinced us that the method in its present 

 form is unreliable but it is possible that other conditions can 

 be found which will permit a separation. If this could be 

 done the method would be exceedingly valuable. 



Sheffield Chemical Laboratory, New Haven, Connecticut. 



