4 PROCEEDINGS OF THE AMERICAN ACADEMY 



122.24 and 122.48. The difference between these extremes corre- 

 sponds to only 1 milligramme in 3 grammes of Sb.,0^, which was 

 about the average amount weighed in these experiments. 



In June, 1861, F. Kessler, of Dantzic, published in Poggendorff's 

 " Annalen " a paper * devoted to a re-examination of the atomic weights 

 of chromium, arsenic, and antimony, based on a method of volumetric 

 analysis which he had previously described in the same journal.t 

 Indeed, in his earlier paper he had already quite fully elaborated the 

 subject, and thus anticipated both Schneider and Dexter in correcting 

 the old number of Berzelius. The method of Kessler was based on 

 the reciprocal relations of potassic dichromate and ferrous chloride ; 

 and, as is well known, standard solutions of these salts are especially 

 well adapted to volumetric determinations, by the circumstance that 

 the neutral point can be so accurately fixed by the reaction with 

 potassic ferricyanide. For the details of the method, which were quite 

 numerous and complicated, we must refer to the original paper. It is 

 sufficient for the present purpose to say that the atomic weight of anti- 

 mony was thus indirectly referred to the molecular weight of potassic 

 chlorate, which was taken as 122.57, according to the determinations of 

 Pelouze and of Marignac. Kessler experimented with antimony, with 

 antimonious oxide, and antimonious chloride, and obtained results vary- 

 ing between 121.67 and 122.61. We translate his own commentary: 

 " Although the results of these experiments, taken as a whole, agree very 

 nearly with those obtained by Dexter, I must nevertheless confess that 

 I am not wholly convinced that our number, which is two hydrogen 

 units higher than that found by Schneider, is much nearer the truth 

 than his. Every one who has occupied himself with the analysis of 

 different antimony compounds must be able to indorse what Berzelius 

 wrote in 1812: 'I have never worked with a material with which it 

 was so extremely difficult to obtain constant results.' . . . Neverthe- 

 less, I believe I have been able to show that in the analysis of anti- 

 mony compounds the volumetric method is capable of affording a very 

 sharp control over results obtained in other ways." 



Before the Academie des Sciences in Paris, in 1857 and 1858, J 

 Dumas read the results of his celebrated revision of the atomic weights 

 of the chemical elements, during' which he redetermined the atomic 

 weight of antimony. § With this, as with most of the other elements 



* Poggendorff's Annalen, cxiii. 134, June, 1861. 



t Ibid., xcv. 204, June, 1855. 



t The 9th of November, 1857, and the 27th of December, 1858. 



§ Annales de Chimie et de Physique, 3me Series, LV. 175, February, 1859. 



