338 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



Hence the subjoined percentages of Ta^Og from TaCl.,, and the ratios 

 5AgCl : TaClj : : 100 : x, and lOAgCl : TaoO^ : : 100 : a;; 



Mean, 60.889, ± .0208 49.611, ± .289 30.153, ± .180 



From these ratios we get for the atomic weight of tantalum : 



Prom per cent. Ta-A Ta = 173.74 



From SAgCltTaClj " =178.27 



From 10AgCl:Ta.O3 " =176.10 



These results are too low, and their " probable errors " are not worth 

 computing. Probably Blomstrand's material still contained some colum- 

 bium. 



In 1866 Marignac's determinations appeared.' He made four analyses 

 of a pure potassium fluotantalate^, and four more experiments upon the 

 ammonium salt. The potassium compound, KoTaF^, was treated with 

 sulphuric acid, and the mixture was then evaporated to dryness. The 

 potassium sulphate was next dissolved out by water, while the residue 

 was ignited and weighed as TaoO,. One hundred parts of the salt gave 

 the following quantities of Ta^Oj and KoSO^ : 



TcuOs. E.SO,. 

 56.50 44.37 



56.75 44.35 



56.55 44.22 



56.56 44.24 



Mean, 56.59, ± .037 Mean, 44.295, ± .026 



From these figures, 100 parts of KjSO^ correspond to the subjoined 

 quantities of TagO-, : 



127.338 

 127.960 

 128.178 

 127.848 



Mean, 127.831, ±: .120 



^ Arch. Sci. Phys. Nat. (2), 26, 89. 1866. Oeuvres Completes, 2, 314. 



