116 ATOMIC WEIGHT DETERMINATIONS. 



TANTALIUM. 



Deville and Troost liave determined the vapor density of 

 tantalium chloride. It agrees with an atomic weight of 

 182. [Paris Comptes Bend., 6i, 1867, 29-4.) 



J. J. Berzelius : 167.74 (0 = 16). 



Berzelius decomposed the sulphide in dry chlorine gas 

 and decomposed the resulting chloride with water. 99.75 

 parts sulphide yielded 89.35 tantalic acid. On the suppo- 

 sition that the acid contains three atoms of oxygen Berze- 

 lius calculates the atomic weight at 1148.365 for S = 200.75. 

 [If the acid contains five atoms of oxygen the value becomes 

 167.74.] (PoggencL Ann., 4, 1825, 14, and Lehrbuch, 3, 

 1209.) 



Rose denies that the sulphide formed, as Berzelius pre- 

 pared it, by heating tantalium in carbon disulphide vapor 

 is a constant compound. [Poggend. Ann., 99, 580.) Alarig- 

 nac, however, shows that Berzelius, Rose and Hermann, 

 obtained constant results from its analysis, from 89.50 to 

 90 acid from 100 sulphide. If Ta == 182, the sulphide 

 would give 90.24 acid. {Liebifs Ann., S, 4., 1866, 358.) 



H. Rose : 172 (O = 16). 



Out of twelve analyses of the chloride, in which both 

 the chlorine and the tantalic acid were determined, Rose 

 selected two in which the agreement was best. [These 

 analyses calculated for Ag = 107.93, 01 = 35.457, give Ta 

 = 171.96.] The chloride was prepared from tantalic acid 

 especially freed from tungsten and tin by mixing with car- 

 bon, drying in carbon di-oxide, and heating in a current of 

 chlorine in which the salt was allowed to cool. Excess of 

 chlorine was expelled by dry air, and the salt was hermeti- 

 cally sealed in glass. Rose supposed the acid to contain 

 two atoms of oxygen and therefore deduces the value 859.81 

 (0 = 100). {Poggend. Ann., 99, 1856, 75.) 



Marignac seems to prove that the material with which 

 Rose dealt contained niobium. He states that the chlorides 

 of the two elements cannot be separated from one another, 

 and that there are no characteristics by which their purity 

 can be decided. {Liebig's Ann., S, 4, 1866, 352.) 



