428 RECORD OF SCIENCE FOR 1887 AND 1888. 



mean, Si =28.332. Meyer aud Seubert's values lor O aud Br. were used 

 in calculatiug. (Journ. Chein. Soc, Juue, 1887.) 



Thorium. — From eight analyses of the sulphate, Kriiss and Nilson 

 find in mean Th = 231.869, when = 15.90 and 8 = 31.98. (Beiichte, 

 XX, 1665.) 



Osmium. — The atomic weight of osmium has had peculiar interest 

 from the fact that the value ordinarily assigned to it v.as out of har- 

 njony with the periodic law. The constant has been re-determined by 

 Seubert, who analyzed after usual methods the osmichlorides of am- 

 monium and x^otassium. His results may be computed in the form of 

 eight ratios, which give values for Os varying from 1 89.72 to 192.00. The 

 mean of all is Os = 191.12; which Seubert regards as still slightly too 

 high. Meyer and Seubert's figures for Ag, K, N, and CI were used in 

 the calculations, with H = l. (Berichte, xxi, 1839.) 



Platinum. — Dittraar and McArthur, from experiments of a complex 

 kind upon the chloroplatinates of potassium, ammonium, and rubid- 

 ium, conclude that Seubert's determination, Pt = 194.8, is too low, 

 and that 195.5 is more nearly the correct value. (Trans. Roy. Soc. 

 Edinburgh, xxxiii, 561.) 



Seubert replies to the foregoing paper, and maintains his own figures. 

 He also calls attention to the fact that his results had been fully con- 

 firmed by Halberstadt. (Berichte, xxi, 2519.) 



Ruthenium. — Kedetermined by Joly, who gives Ru = 101.5, without 

 particulars. (Compt. Rend., cvir, 997.) 



Gold. — Kriiss determines the atomic weight of gold by means of five 

 ratios, representing the neutral chloride, An CI3, and the salt K An Br4. 

 The chloride Mas reduced by sulphurous acid, the gold was weighed as 

 metal, and the chloride as silver chloride. Eight such experiments gave 

 in mean Au = 196.622. The double bromide gave the following ratios : 



K An Br4 : An, nine experiments An =r 196.741. 



4AgBr: An, five experiments An = 196.743. 



Br;: Au, fonr experiments An=;iy().619. 



K Br: An, four experiments Au = 196.697. 



The final value, rejiresenting thirty experiments, was Au = 196.697, 

 H being taken as unity, with Stas' values for Ag, (31, K, and Br. 

 (Berichte, xx, 205.) 



The same constant was also measured by Thorpe and Laurie, who 

 likewise made use of the double salt K Au Br^. Three ratios were 

 taken : First, the salt was decomposed by heat, and the residual Au, and 

 K Br, were both weighed. Secondly, the K Br from the former series 

 was titrated with silver solution, giving the ratio Au : Ag. Thirdly, 

 the Ag Br found in the last reaction was also weighed, giving the ratio 

 Au : Ag Br. Taking H = 1 and Stas' figures for Ag, K, and Br, we have : 



From An : K Br, eight experiments An = 196.876. 



From Au : Ag, nine experiments An = 196.837. 



From Au : Ag Br, eight experiments An = 196.852. 



Mean of all An = 196.852. 



• 



(Journ.- Chem. Soc, June, 1887.) 



