FUNDAMENTAL PROPERTIES OF THE ELEMENTS RICHARDS. 207 



greater than the contraction which takes place on forming several 

 other oxides, and he ascribed this effect to the well-known differences 

 of affinity in these cases; but he did not carry the idea further. 

 Long afterwards, Braun, 1 Mueller-Erzbach, 2 Hagemann, 3 and Traube, 4 

 independently and apparently without knowledge of each other's 

 work, called attention to other cases of similar relationships. 



All of these researches have produced so little effect on the litera- 

 ture of the subject 5 that they were entirely overlooked during the 



COMPARISON of HEATS OF FORMATION of CHLORIDES 

 and CONTRACTION ON COMBINATION 



-200 

 CAL 



HEAT OF FORMATION 







ON COMBINATION 



W 







Fig. 2. 



earlier part of the present investigation. The oversight mattered 

 little, however, because the whole subject needed a fresh attack. 

 Essential factors in the situation had not been noticed by any of 

 these earlier investigators. Affinities, indeed, had been considered, 

 but the nature of the substances on which the affinities act had been 

 overlooked. Evidently the change of volume in any case must de- 

 pend not only on the intensity of the pressure exerted by the affinity, 

 but also, among other tilings, on the compressibility of the sub- 



1 V. Braun, see Johnson, Journal Chemical Society Transactions, 1877, vol. 31, p. 252. 



2 Mueller-Erzbach, Ber., d. deutsch. Ch. Ges., 1881, vol. 14, pp. 217, 2043. 



3 Hagemann (private publication, Friedlander, Berlin, 1900). 



4 Traube, Ueber den Raum der Atome, Ahrens's Sammlung der chem. und chem.-techn. Vortrage, vol. 

 4, p. 256. 



5 See, for example, Ostvvald's Gundriss der allgemeinen Chemie, 1899, p. 185. 



