104 ATOMIC WEIGHT DETERMINATIONS. 



J. J. Berzelius : 79.23 (O = 16). 



Berzelius found that 100 Se absorb 179 dry chlorine gas, 

 and that the product was exactly decomposed by water into 

 chlorhydric acid and selenious acid. [If CI = 35.457 (Stas) 

 the value follows.] [Poggend. Ann., 8, 1826, 21.) 



F. Sacc : 78.65 (0 = 16) ; 490.93 (O = 100). 



Sacc's experiments are very discordant. He made three 

 experiments on the reduction of a known weight of sele- 

 nious acid with ammonium bisulphite and chlorhydric acid. 

 The mean result was Se = 490.38 ; extreme difference, 5.5. 

 In four experiments barium seleniate was decomposed by 

 heating to redness with sulphuric acid in excess. The salt 

 was found to contain 41.95 selenious acid ; extreme differ- 

 ence 0.04. For Ba = 856.877 the resulting value is 491.49. 

 The selenium was purified by solution in nitric acid, evap- 

 oration and sublimation, and by reduction with HCl and 

 ammonium bisulphite. Selenious acid was prepared by 

 oxidation with nitric acid. Barium seleniate was prepared 

 by precipitation of barium nitrate with sodium seleniate and 

 heating to redness. Sacc regards 490.3 as the most prob- 

 able value of Se. {Annal. de Chim. etde Phgs., (3,) 31, 1851, 

 119.) 



A. SCHROETTER : 78.6 (O = 16). 



Details not given. {Kopp's Jahresbericht, 4^, 1851, 318; 

 Sitz.-Bericht der k. k. Acad., 6, 1851, 214.) 



Erdmann and Marchand : 78.6 (O = 16) ; 492.5 

 (0 = 100). 



Determined from experiments on mercuric selenide by 

 the same niethods employed for the determination of S, 

 q. v. Three experiments gave 71.726, 71.731, 71.741, per 

 cent, mercury. {JSrdmami's Journ. fur Prak. Chem., 55 y 

 1852, 202.) 



J. Dumas : 76.46 (O = 16). 



Determined by seven experiments on the chloridation of 

 selenium. The chloride was condensed in a tube cooled to 

 — 20°, after which the escaping gases were led through 

 other tubes filled with asbestos. The extreme difference 

 in the results was 0.46. CI = 35.5. {Annal. de Chim. et de 

 Phys., (3,) 55, 1859, 129.) 



