336 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



50.135 38.366 19.234 



49.662 



49.813 38.073 18.966 



49.666 



50.000 38.238 19.119 



49.807 



Mean, 49.806, ± .045 Mean, 38.566, ± .108 Mean, 19.205, ± .043 



From these means the atomic weight of columbium may be computed, 

 thus: 



From 2CbCl5:CbA, Cb = 96.231 



From CbCljiSAgCl " ==99.107 



From 5AgCl:CbA "=97.641 



when Ag = 107.88, and CI = 35.4584. 



The series upon sodium columbate, which salt was decomposed with 

 sulphuric acid, both CbaOg and Na2S04 being weighed, is too discordant 

 for discussion. The exact nature of the salt studied is not clear, and the 

 data given, when transformed into the ratio Na^SO^ : CboO- : : 100 : x, 

 give values for x ranging from 151.65 to 161.20. Further consideration 

 of this series would therefore be useless. It seems highly probable that 

 Blomstrand's materials were not entirely free from tantalum, since the 

 atomic weight of columbium derived from his analyses of the chloride 

 is evidently too high. 



Marignac ^ made about twenty analyses of the potassium fluoxycolum- 

 bate, CbOFg.SKF.HoO. One hundred parts of this salt give the follow- 

 ing percentages: 



Cb,05 Extremes 44.15 to 44.60 Mean, 44.36 



KoSO, " 57.60 " 58.05 



H„0 " 5.75 " 5.98 



F " 30.62 " 32.22 



From the mean percentage of CbsO^, Cb = 93.478. 



From the mean between the extremes given for K,jS04. Cb = 93.95. 



The recent determinations by Balke and Smith ' are much more sat- 

 isfactory than those already cited. Their material was certainly purer, 

 and the results obtained were highly concordant. Columbium penta- 

 chloride was decomposed by water, with the aid of a little nitric acid, 



1 Arch. Sci. Phys. Nat. (2), 23. 1865. Oeuvies Completes, 2, 259. 

 - Journ. Amer. Chem. Soc. , 30, 1644. 1908. 



