344 Prof. J. Traube on the 



arrive, as a result of my researches, at the following funda- 

 mental proposition regarding atomic space: — 



The space occupied by an atom changes from one compound 

 to another; it is the smaller the greater the affinity of the atom 

 in question for the neighbouring atoms with which it is combined. 



The importance of this proposition lies, on the one hand, 

 in the conception of atoms as compressible spheres, and, on the 

 other, in the fact that the contraction of the atom is regarded 

 as a measure of chemical affinity. Special attention must be 

 drawn to the fact that the atomic contraction forms the only 

 measure of chemical affinity; and although Richards cannot 

 claim priority regarding the above and a few other propo- 

 sitions enunciated by him, he has rendered one of the most 

 valuable services by showing * that in general the change in 

 the free energy is just as little a measure of the chemical 

 energy as the heat development. 



In accordance with the above I have propounded the 

 problem of calculating the atomic contractions from the 

 results of chemical reactions, considering this to be the most 

 important problem of chemical dynamics t (Mechano-chemie) — 

 the sister science to thermo- chemistry. 



The effect due to " affinity pressure " must be similar to 

 that due to other pressures, and in particular to the intrinsic 

 pressure of liquids, which in most cases amounts to about 

 1000 atmos. at 0°. From this it follows that the true atomic 

 volumes corresponding to the liquid state must frequently be 

 considerably less than those corresponding to the gaseous 

 state, and that accordingly during evaporation not only the 

 co-volume, but the true volume of the atoms as well, 

 frequently undergo very considerable expansion. 



A gason is greater than a fiuidon. By means of this 

 simple doctrine of the compressibility of atoms, among other 

 things various difficulties of van der Waals' theory may be 

 explained, notably the third volume of the isothermals may be 

 interpreted %. 



* Zeitschr. Physik. Chem. Bd. xlii. p. 129 (1903). 



t Cf. my Grundriss der Physik. Chemie. 



% Cf my Grundriss der Physik. Chem, p. 107, 1904. I had also 

 (cf. Drude's Ann. Phys. (4) Bd. viii. p. 2G7, 1902, and Zeitschr. anorg. 

 Chem. Bd. xxxvii. p. 226, 1903, and Bd. xxxviii. p. 399, 1904) appealed 

 to the theory of gasons and fluidons in order to interpret the observations 

 of de Heen, Galitzin, and especially also those made in my laboratory by 

 Teichner, which apparently are not in accordance with Andrews' theory 

 of the critical state. 1 note that — as Teichner and Bakker have shown 

 (Zeitschr. Physik. Chem. Bd. li. p. 345, 1905) — other suppositions are 

 also possible. But when Verschaffelt (in the Berichte der Akad. von 

 Wetenschappen, Amsterdam, 24, Dec. 1904) once more attempts to 

 minimize Teichner's experiments by ascribing them to the effect of slight 



