ATOMIC WEIGHTS 339 



The ammonium salt, (NHJ^TaF^, ignited with sulphuric acid, gave 

 these percentages of TaoOg. The figures are corrected for a trace of 

 K2SO4 which was always present: 



63.08 

 63.24 

 63.27 

 63.42 



Mean, 63.25, ± .047 



Hence we have four values for Ta : 



From potassium salt, per cent. Ta.Os Ta = 183.55 



From potassium salt, per cent. K2SO4 " =182.93 



From potassium salt, K2S04:Ta205 " ^182.76 



From ammonium salt, per cent. Ta^Oj " := 182.66 



Average Ta = 182.975 



The determinations by Hinrichsen and Salilbom ' were much simpler. 

 Metallic tantalum was converted into pentoxide by heating in oxygen, 

 and the composition of the oxide was so ascertained. The weights and 

 percentages of tantalum are as follows: 



.0111 



Hence Ta= 181.019. 



In this instance, as in the case of columbium, the latest determination 

 supplants the others. Until further evidence is available the atomic 

 weight of tantalum may be taken as 181. The uncertainty probably 

 amounts to as much as a unit. 



1 Ber. Deutsch. chem. Ges., 39, 2600. 1906. 



