SMITH. 



EXPANSION OF ETHER AND ALCOHOL. 



447 



Application to the van der Waals a. 



[A considerable part of the following discussion was written by 

 Professor Hall.] 



It has already been pointed out that the determination of the coeffi- 

 cients e and k in the neighborhood of the boiling condition was under- 

 taken on account of the importance which is attached to them in the 

 study of the van der Waals a. Professor Hall, in the discussion re- 

 ferred to at the beginning of this paper, dealt with two assumptions 

 relating to the liquid and the vapor conditions : 



TABLE IX. 

 Compressibility of Ethyl Alcohol in the Superheated State. 



" 1, That the pressure due to molecular attraction within a fluid is 

 -^, where v is the specific volume and a is some constant ; 



" 2, That the energy per molecule, aside from the potential energy 

 due to the attraction just mentioned, is a function of temperature 

 only, so that it remains constant during any isothermal change of 

 state." 



Using the data of Amagat for the expansibility and the compressi- 

 bility of ethyl ether and ethyl alcohol, he found that, if assumption 2 

 held good, ^^ assumption 1 could not be true for either of these sub- 

 stances in the liquid state, and that, on the contrary, 



^^ I do not commit myself to the opinion that assumption 2 is necessarily 

 true. It is quite possible tliat we have in both liquid ether and liquid alcohol 

 some peculiar state of aggregation of the molecules in pairs or triplets or otlier 

 small groups such as Sutherland has shown the probability of in the case of liquid 

 water. If such groups do not exist in a given liquid, we should, according to the 

 van der Waals hypotheses, expect both assumption 1 and assumption 2 to hold. 

 If such groups do exist in a given liquid, and if their number is independent 



