COLUMBIUM. 235 



49.662 ...... ...... 



49.813 38-073 18.966 



49.666 ...... ...... 



50.000 3 8 -238 19.119 



49.807 



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



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

 thus: 



From 2CbCl 5 : Cb 2 O 5 ........................ Cb 95.397 



From CbCl 5 : 5AgCl ........................ ";== 98.477 



From 5 AgCl : Cb 2 O 5 ........................ = 96.933, 



when == 15,879, Ag = 107.108, and Cl = 35.179. 



The series upon sodium columbate, which salt was decomposed with 

 sulphuric acid, both Cb 2 5 and Na 2 S0 4 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 2 SO 4 : Cb 2 6 : : 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 nuoxy colum- 

 bate, CbOF 3 .2KF.H 2 O. 100 parts of this salt give the following percent- 

 ages : 



Cb 2 O 5 ............ Extremes 44.15 to 44.60 Mean, 44.36 



K 2 SO,... ......... 57.60-58.05 



H 2 ............. " 5.75 " 5.98 



F ................ " 30.62 " 32.22 



From the mean percentage of Cb 2 O 5 , Cb = 92.852. If = 16, this 

 becomes 93.56. 



From the mean between the extremes given for K 2 S0 4 , Cb = 93.192. 

 If = 16, this becomes 93.90. 



As Beville ami Troost'sf results for the vapor density of the chloride 

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

 as approximately correct. The mean of the two values computed from 

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



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

 f Compt. Rend., 56, 891. 1863. 



