235 



Mean, 49.S06, d= .045 Mean, 38.566, ± .108 Mean, 19.205, ±: .043 



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

 thus: 



From aCbClj : CbPj Cb = 95-397 



From CbCIs : SAgCl " = 98-477 



From 5AgCl : Cb^O^ " = 96-933, 



Avhen = 15,879, Ag = 107.108, and CI = 35.179. 



The series upon sodium columbate, which salt was decomposed with 

 sulphuric acid, both Cb.,05 and Na.^SO^ 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^ : Cb.^Oj : : 100 : a;, 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 Blom- 

 strand's materials were not entirely free from tantalum, however, since 

 the atomic weight of columbium derived from his analyses of the chloride 

 are evidently too high. 



Marignac* made about twenty analyses of the potassium fluoxycolum- 

 bate, CbOF,.2KF.H.,0. 100 parts of this salt give the following percent- 

 ages : 



CbjOj Extremes 44.15 to 44.60 Mean, 44.36 



KjSO, " 57.60 "58.05 



HP " 5.75 " 5.98 



F " 30.62 " 32.22 



From the mean percentage of Cb^Oj, Cb= 92.852. If = 16, this 

 becomes 93.56. 



From the mean between the extremes given for K.^SO^, Cb = 93.192. 

 If = 16, this becomes 93.90. 



As Deville and Troost's f results for the vapor density of the chloride 

 and oxychloride agree fairly well with Cb = 94, we may adopt this value 

 as approximately correct. 1 The mean of the two valiies computed from 

 Marignac's data is 93.022 when H = 1, and 93.73 when = 16. 



* Arch. Sci. Phys. Nat. (2), 23. 1865. 

 t Compt. Rend., 56, 891. 1863. 



