igo/f\ Mills — Molecular Attraction. 81 



2. The belief based on the study of the specific heat of 

 gases, that the total energy of a gaseous molecule, exclusive 

 of the energy which holds the molecule together and of 

 extraneous forces, is proportional to the translational energy. 



4. The inference, for it is somewhat more than a mere 

 assumption, the causes for 3 being considered, that the total 

 energy of a molecule of a liquid would similarly be found to 

 be proportional to its translational energy. 



These four preliminary steps may be summed up by the 

 statement that the total energy per se of a molecule must be 

 the same in the liquid as in the gaseous state, the tempera- 

 ture being the same. If at a given temperature a given 

 weight of gas represents more energy than the same weight 

 of the substance as a liquid; the extra energy of the gas must 

 be energy of position only (assuming no intramolecular 

 change). 



We made no attempt in the former paper, and we make 

 none in this, to prove the last statement above, or to give the 

 evidence for it. To do so even cursorily would require a dis- 

 cussion of the kinetic theory of gases, their specific heats 

 more particularly, and the modern theories of solution. The 

 statement is here made only as the belief of the author upon 

 which the present work is based. Many citations of closely 

 related belief might be given. Oswald 1 gives a clear and 

 succinct statement of 1 and 2. O. E. Meyer 2 shows the 

 grounds for 3. The author has published 3 the study which 

 led him to conclude that 4 was a reasonable supposition. So 

 long ago as 1885, Ramsay and Young made practically the 

 same statement. 4 



1 Solutions pp. 147, 148. 



2 Kinetic Theory of Gases, p. 117. 



8 Journal of the Elisha Mitchell Scientific Society, Vol. 18 (1902). 



*Phil. Trans. 1886A, Evaporation and Dissociation, p. 72, Section 

 4; c and d of that section not being necessary under the limitation imposed 

 above that there should be no intramolecular change, and e and the foot- 

 note being unnecessary in the light of the later work of van 't Hoff . 



