92 Dr. R. D. Kleeman : Determinations of the Law of 



be proved that the law o£ molecular attraction is independent 

 of the temperature, it can be completely determined from 

 surface-tension data. Let us then determine the law of 

 attraction assuming that this can be proved. If we assume 

 that the attraction varies inversely as the eleventh power of 

 the distance between the molecules, we obtain the equation 

 \ = F(/o 1 — p 2 ) 4 for the surface-tension, where F is a constant 

 which is independent of the temperature but depends on the 

 nature of the liquid. This equation is at once obtained by 



substituting -^ for (/> {z)iX\/m i y in the general equation 



for the surface-tension given by the writer and quoted in a 

 previous part of the paper. According to the equation 



^should be a constant for each liquid, and this is 



approximately the case as will appear from Table I. * Now 

 if the law assumed is true it should also give a formula 

 for the latent heat agreeing with the facts. Substituting 



-^ for <$>{z)(Xx/mi) 2 in the general equation for the latent 



heat quoted, we obtain L = H (p\ 0/3 — pl°^), where H is a con- 

 stant which should depend only on the nature of the liquid. 

 But H or L/pl ' 3 — pl° /s is not constant for the same liquid, 

 as is shown by Table J. The attraction between two mole- 

 cules a given distant apart cannot therefore he independent 

 of their temperature. 



Table I. 





Benzene. 



Chlorobenzene. 



Carbon tetra- 

 chloride. 



Methyl 

 formate. 



T 



X 



353 

 467 

 198 



433 

 467 

 210 



503 



48-5 

 267 



423 

 21-3 

 75 4 



473 

 21-1 

 84 3 



533 

 21-4 

 102 



363 

 401 

 11-6 



433 

 403 

 139 



503 

 41-5 

 180 



303 

 27-5 

 123 



363 

 27-4 

 139 



423 



27-9 

 174 



(Pi-P 2 ) 4 " 

 L 



plO/3 — plU/3"' 



* The values of X contained in the tables in this paper are taken from 

 a paper by Ramsay and Shields, Phil. Trans, of the Royal Society, 

 vol. clxxxiv. p. 647 (1893), and the values of L, p,, and p 2 , are taken 

 from the papers by Mills quoted previously, who calculated values of L 

 by Olapeyron's equation using the density and pressure data of Ramsay 

 and Young. 



