ATOMIC WEIGHT DETERMINATIONS. 



ALUMINIUM. 



The specific heat of aluminium, as determined by Regnault 

 aad by Kopp, and the vapor density of volatile compounds, 

 as determined by Deville and Troost and by Odling, indicate 

 that the atomic weight of this element is about 27.5. (Gme- 

 lin-Kraut, Handbueh der Chemie, 1, 39; and L. Meyer, Modeme 

 Theorien der Chemie, 50.) 



J. J. Berzelius : S7.S67 (0 = 16). 



100 parts of anhydrous aluminic sulphate decomposed by 

 heat, gave 29.934 parts of oxide. Preparation not described. 

 Number of experiments, probably 1. In Berzelius' Lehrbuch 

 these data are calculated for S = 200.75, and give Al = 

 170.9 (O = 100,) or 37.3U (O = 16.) [If S = 32, the data 

 give Al = 27.267.] {Poggend. Ann., S, 1826, 187.*) 



T. Thomson: 30 (O = 16).t 



Thomson found, probably from analysis of the sulphate, 

 (see appendix.) that 125 Al = 100 0. Thomson supposed 

 aluminic oxide to be a protoxide. [If it is a sesqui-oxide, 

 the data give Al at 30.] {Thomson's System of Chemistry, 7th 

 €d., 1, 1831, 454.) 



W. W. Mather: 20.55 (0 = 16). 



According to this chemist 0.646 grammes of chloride, 

 prepared according to Woehler, gave 2.055 grammes argen- 



* This article by Berzelius, which contains the particulars of a large part 

 of his earlier atomic weight determinations, will be referred to frequently 

 in the course of this paper. It is unfortunately full of misprints, all of 

 which are, by no means, corrected in the table of errata at the end of the 

 volume. The correctly printed values of the atomic weights discussed in 

 it are to be found in Poggend. Ann., lo, 1827, 339. 



f It must be remarked, in justice to Dr. Thomson, that his atomic weight 

 determinations are, properly speaking, of a different nature from those of 

 other chemists. So thoroughly persuaded was he of the truth of Front's 

 hypothesis, (that the atomic weights of the elements are all exact multiples 

 of that of hydrogen,) that his experiments were directed merely towards 

 ascertaining which multiple, in any case, was to be adopted. 



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