14 ATOMIC WEIGHT DETERMINATIONS. 



oxide. If C = 75.4, and S = 200, the value follows. {Phil 

 Trans., lOJ^, 1814, 20.) 



J. J. Berzelius : 136.79 (O = 16). 



100 parts of barium chloride gave 138.08 and 138.06 parts 

 argentic chloride. [If Ag = 107.93, and CI = 35.457, the 

 above value follows.] Berzelius also determined barium 

 from the sulphate ; 100 parts barium chloride gave 112.17 

 and 112.18 parts sulphate. Calculated for S = 200.75 this 

 determination is almost identical with the other; Berzelius, 

 however, expressly adopts the former. [Calculated for S = 

 32.0742, it gives 135.74.] {Poggend. AnnaL, 8, 1826, 189, 

 and Lehrbuch der Chemie, 5th ed., 3, 1229.) 



E. Turner: 137.4 (0 = 16). 



Turner determined the chlorine contents of barium chlo- 

 ride at 34.016 per cent, by precipitation with- silver. This 

 number was the mean of the best two experiments made, 

 and the value follows from it on the assumption that CI =: 

 85.42. The barium chloride was prepared from native car- 

 bonate by solution in chlorhydric acid, precipitation of 

 impurities with barium oxide, ignition of the chloride, treat- 

 ment with alcohol, and recrystallization. {Pfdl. Trans., 119, 

 1829, 291.*) 



T. Thomson : 136 (0 = 16) ; 850 (O = 100). 



Thomson had formerly determined this atomic weight at 

 875 by mixing potassic sulphate with barium chloride in 

 such proportions that the supernatant liquid contained no 

 sensible amount of either sulphuric acid or barium. Turner 

 having shown the fallacy of this method, Thomson substi- 

 tuted ammonium sulphate, and also sulphuric acid for the 

 potassium salt, and found 9.5006 barium oxide equivalent to 

 5.00 sulphuric anhydride. lie also analyzed the chloride 

 with argentic nitrate, assuming silver = 1375, and chlorine 

 = 450, and reached the same conclusion with reference to 

 barium. {Thomson's System of Chemistry, 7th ed., 1, 1831, 

 426.) 



* Turner made the discovery in the course of this investigation that 

 barium sulphate curries down other salts, such as potassic sulphate, wliich 

 cannot he extracted from the precipitate h,y any degree of washing, and that 

 determinations, with harium sulphate, are consequently unreliable. Al- 

 though Berzelius drew attention to the importance of the observation, and 

 Thomson was obliged to acknowledge errors in his work from this cause, 

 the fact was for a long time nearly forgotten, as can readily be proved from 

 the contents of this digest. 



