Z PROCEEDINGS OP THE AMERICAN ACADEMY 



in a flask witli idtiic acid, and the mass evaporated to dryness in 

 a platinum crucible is heated until it becomes perfectly white, the 

 same results are always obtained," nevertheless, in the paper cited, 

 he does not give the several determinations on which his conclu- 

 sion was based, or any details by which we can now judge of the 

 purity of the metal used. He simply gives the single result just 

 cited, from which we readily deduce as the atomic weight of antimony 

 129; and with this value he appears to have been contented; for we 

 find in his masterly review of the atomic weights of the chemical ele- 

 ments, published in 1826,* the same value given, without further 

 comment, and it remained unquestioned for more than thirty-eight 

 years. 



Not until 185G does any farther investigation of the subject appear 

 to have been made. In February of that year, R. Schneider, of Berlin, 

 published a preliminary notice ;t and later, in May, the full detailsj of 

 a new determination of the atomic weight of antimony, made by a 

 method wholly different from that of Berzelius. This method con^ 

 sisted in reducing a pure native sulphide of antimony by hydrogen 

 gas. The material selected was the antimony glance of Arnberg, whicii 

 is distinguished for its high degree of purity, and by appropriate tests 

 the mineral was shown to be free from arsenic and the metals which 

 usually accompany antimon}'. The only impurity that could be dis- 

 covered was a small amount of quartz, which is associated with the 

 mineral as gangue ; but this was of no importance, since the amount 

 could be determined in every experiment with almost absolute preci- 

 sion. The same was almost equally true of two well-known defects in 

 the process, which, if not allowed for, would become sources of error; 

 namely, the escape in vapor, or, mechanically, of a small amount of 

 sulphide of antimony during the reduction, and the circumstance that 

 a further small amount of sulphide escapes reduction by becoming 

 enclosed in the regulus. The first of these effects would diminish, and 

 the second increase, the weight of the regulus ; and the same effects 

 would also respectively diminish or increase the atomic weight of anti- 

 mony calculated from the observations. The two sources of error evi- 

 dently tend to balance each other ; but, on the other hand, the effect of 

 the last is several times greater than that of the first. The total effect, 

 however, is but small; and, had these known sources of error been 



* Poggendorff's Annalen, viii. 23, 1826. 

 t Ibid., xcvii. 483, February, 1856. 

 t Ibid., xcviii., 293. May, 1856. 



