216 THE ATOMIC WEIGHTS. 



ANTIMONY. 



After some earlier, unsatisfactory determinations, Berzelius,* in 1826, 

 published his final estimation of the atomic weight of antimony. He 

 oxidized the metal by means of nitric acid, and found that 100 parts of 

 antimony gave 124.8 of Sb 2 O 4 . Hence, if O 16, Sb = 129.03. The 

 value 129 remained in general acceptance until 1855, when Kessler, f by 

 special volumetric methods, showed that it was certainly much too high. 

 Kessler's results will be considered more fully further along, in connec- 

 tion with a later paper; for present purposes a brief statement of his 

 earlierj conclusions will suffice. Antimony and various compounds of 

 antimony were oxidized partly by potassium dichromate and partly by 

 potassium chlorate, and from the amounts of oxidizing agent required 

 the atomic weight in question was deduced : 



By oxidation of Sb 2 O 3 from 100 parts of Sb Sb = 123.84 



By oxidation of Sb with K 2 Cr 2 O 7 " 123.61 



By oxidation of Sb with KC1O 3 + K 2 Cr 2 O 7 " = 123.72 



By oxidation of Sb 2 O 3 with KC1O 3 + K 2 Cr 2 O 7 . . . " = 123.80 



By oxidation of Sb 2 S s with K 2 Cr 2 O 7 " = 123.58 



By oxidation of tartar emetic " = 1 19.80 



The figures given are those calculated by Kessler himself. A recalcu- 

 lation with our newer atomic weights for O, K, Cl, Cr, S, and C would 

 yield lower values. It will be seen that five of the estimates agree closely, 

 while one diverges widely from the others. It will be shown hereafter 

 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 J pub- 

 lished some results obtained by the reduction of antimony sulphide in 

 hydrogen. The material chosen was a very pure stibnite from Arnsberg, 

 of which the gangue was only quartz. This was corrected for, and cor- 

 rections were also applied for traces of undecom posed 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 3.2 to 10.6 grammes of material were taken in each ex- 

 periment. The final corrected percentages of S in Sb 2 S 3 were as follows : 



28.559 

 28.557 

 28.501 



28.554 

 28.532 



*Poggend. Aimalen, 8, i. 



tPoggend. Annalen, 95, 215. 



I Poggend. Annalen, 98, 293. 1856. Preliminary note in Bd. 97. 



