538 Dr. "R. D. Kleeman on the 



of each cube has two different molecules adjacent to it. Tt 

 will be easily seen on considering this distribution that it 

 satisfies each of the above conditions. 



Tt will also at once be recognized that it' the relative con- 

 centration remains the same in a mixture when its density 

 changes, the relative distribution of the molecules is unaltered, 

 all the distances of separation of the molecules being increased 

 in the same proportion by a change in density. 



Heat of Mixture of two or more different Liquids. 



Let us first obtain a formula for the heat of mixture of 

 n x grams of the liquid 1 and n 2 grams of the liquid 2, on 

 the supposition that no new molecules are formed in the 

 mixture. 



The mixing may be supposed to take place in the following 

 way. Suppose the two liquids to evaporate into an infinitely 

 large chamber, and let the work done against the attraction 

 of the molecules in the process be denoted by L x and L 2 

 respectively. Let the mixture of vapours be now compressed 

 till it is converted into liquid, and let the heat given out due 

 to the attraction between the molecules be L»,f» a . Then on 

 the supposition that the change in internal energy in the 

 process is equal to the change in the potential energy due to 

 the molecular attraction, we have that the heat of mixture H 

 is equal to (Lm,m„ — nj^i — n 2 L 2 ). 



Now according to the law of attraction given at the 

 beginning of the paper 



Ai/p,Y' 3 



L = 



IfAwj (^i/, 



an 



where 



T _A 2 /> 3 y/3 . y— . ■ 



A,=*,(f;,|) „a a,=*,&0 



and x a denotes the distance of separation of the molecules in 

 the liquid, M the molecular weight, and p the density of the 

 liquid*. The form of A 1 and A 2 , it should be noticed, 



depends only on the form of the function $/— , nv). 



The work done in removing a molecule 1 from the mixture 



* Phil. Mag. May 1910. pp. 793-794. 



