570 



Dr. R. D. Kleeman on Molecular Attraction 



By means of equation (5) it may be transformed into 



( n r. n 2/3 



< C -*T 



•), 



(1) 



where A:, a, &c, are universal constants. If we neglect the 

 powers of T higher than the first and put u — 1, the equation 

 for low temperatures becomes 



which is Eotvos' famous equation. It is known that it does 

 not agree well with the facts near the critical point. The 

 preceding equation shows what modifications must be 

 introduced to obtain a better agreement. Equation (1) is 

 the fundamental form of Eotvos' equation based on the 

 law of attraction between molecules. The writer found 

 that a good agreement is usually obtained by retaining only 

 the first power of T, and giving a an appropriate value. 

 This is shown by Table I. which contains the value of k for 



Table I. 



Ethyl Oxide. 

 a = 1-006. 



M 



ethyl Formate. 

 a = 1003. 



T. 



Tc. 



T. 



h. 



T. 



Jc. 



T. 



Jc. 



1-98 



293 



211 



383 



2-06 



293 



1-99 



383 



313 



211 



393 



2-06 



303 



1-99 



393 



1-99 



323 



2-09 



403 



2-05 



313 



1-99 



403 



1-98 



333 



2 07 



403 



2-05 



323 



199 



413 



202 



343 



2-07 



423 



2-02 



333 



1-99 



423 



1-97 



353 



2-07 



433 



2-03 



343 



199 



433 



196 



363 



2-07 



443 



205 



353 



199 



443 



195 



373 



2-07 



453 



207 



363 



1-99 



453 



195 











373 



1-99 



463 



1-92 



two liquids calculated by the above formula, giving v. the 

 values placed at the top of the table. The data used for 

 the calculations were taken from a paper by Eamsay and 

 Shields *. It will be seen that k is practically independent 

 of the temperature and nature of the liquid. The values of 

 a for the substances ethyl acetate, carbon tetrachloride, 

 * Phil. Trans. E. Soc. A. vol. clxxxiv, p. 647 (1893). 



