ANTIMONY. 189 



value 129 remained in general acceptance until 1855, when 

 Kessler,* by special volumetric methods, showed that it was 

 certainly much too high. Kessler's results will be consid- 

 ered more fully further along, in connection with a later 

 paper ; for present purposes a brief statement of his earlier 

 conclusions will suffice. Antimony, and various compounds 

 of antimony, were oxidized partly by potassium anhydro- 

 chromate and partly b}- potassium chlorate ; and from the 

 amounts of oxidizing agent required, the atomic weight in 

 Cjuestion was deduced : 



By oxidation of Sb.^O^ from loo parts of Sb Sb = 123.84 



" Sb with K2Cr,Oj " r= 123.61 



" KCl63+K,Cr,A "=123.72 



" SU/Jg with " " " = 123.80 



SbjSj with K,Cr207 " ;= 123.58 



" tartar emetic " =: 119.80 



The figures given are those calculated by Kessler him- 

 self. A recalculation wdth our newer atomic weights for 0, 

 K, CI, Cr, S, and C, would yield slightly lower values. It 

 will be seen that five of the estimates agree closely, while 

 one diverges widely from the others. It will be shown here- 

 after that the concordant values are all vitiated by constant 

 errors, and that the exceptional figure is after all the best. 



Shortly after the appearance of Kessler's first paper, 

 Schneider t published some results obtained by the reduc- 

 tion of antimony sulphide in hydrogen. The material 

 chosen was a very pure stibnite from Arnsberg, of which 

 the gangue was onl}- quartz. This was corrected for, and 

 corrections were also applied for traces of undecomposed 

 sulphide carried off mechanically by the gas stream, and 

 for traces of sulphur retained by the reduced antimony. 

 The latter sulphur was estimated as barium sulphate. From 

 0.2 to 10.6 grammes of material were taken in each experi- 

 ment. The final corrected percentages of S in Sb2S3 were 

 as follows : 



* Poggend. Annal., 95, 215. 



f Poggend. Annal., 98, 293. 1856. Preliminary note in Bd. 97. 



