236 THE ATOMIC WEIGHTS. 



TANTALUM. 



The results obtained for the atomic weight of this metal by Berzeliua* 

 Rose,t and Hermann | may be fairly left out of account as valueless. 

 These chemists could not have worked with pure preparations, and their 

 data are sufficiently summed up in Becker's " Digest." 



Blomstrand's determinations, § as in the case of columbium, were 

 made upon the pentachloride. His weights are as follows : 



TaCl,. Ta.,Or,. AgCl. 



.9808 .598 • 



1.4262 .867 2.906 



2.5282 1.5375 5.0105 



1.0604 -6455 2.156 



2.581 1.577 



• 8767 , .534 



Hence the subjoined percentages of Ta205 from TaClj, and the ratios 

 5AgCl : TaCl, : : 100 : x, and 5AgCl : Ta„0, : : 100 : x. 



.180 



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



From per cent. TajOj Ta = 172.342 



From S-^gCl : TaClj , " = 177.055 



From SAgCl : Ta^Og " = 174.821 



These results are too low. Probably Blomstrand's material still con- 

 tained some columbium. , 



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, KjTaF^, was treated with 

 sulphuric acid, and the mixture was then evaporated to dr^'ness. The 

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



* Poggend. Annaleii, 4, 14. 1825. 



t Poggend. Annalen, 99, 80. 1856. 



t Journ. fiir Prakt. Chem., 70, 193. 1857. 



§ Acta Univ. Lund, 1864 



II Arch. Sci. Phys. Nat. (2), 26, 89. 1866. 



