4i8 



SCIENCE PROGRESS. 



entire work in this part of the subject indicates that at 

 extreme dilution the molecular rise for an indifferent solu- 

 tion depends only on the nature of the solvent. 



Influence of the chemical nature of the solvent.- — Accord- 

 ing to equation (9) the molecular rise should be equal to 

 •02T 2 /A. Using Schiff's value for X, viz., 93-4 cal. and T = 

 273 + 8o - 3, the theoretical value of the molecular rise for 

 benzene is 267, which is not far removed from those given 

 above. For alcohol, using- Regnault's value, 214-9 cal. for 

 A and 273 + 78-3 for T, the value of 02T 2 /A is n # 5, 

 which again closely agrees with the numbers obtained from 

 the rise in the boiling-point. The following table contains 

 the mean values to the nearest degree of M' AT jg at extreme 

 dilution as deduced by Beckmann (1890) from observations 

 on different dissolved substances in the solvents named, 

 and also the corresponding values of -02T 2 /A as calculated 

 from the absolute boiling-point and heat of vaporisation. 



The agreement between the two sets of numbers is a 

 satisfactory proof of the validity of the expression — 



M'AT/g = -02P 2 /A. 



Boiling-point and gaseous laws. — This equation corre- 

 sponds, therefore, with the results of experiment, and like 

 Raoult's vapour-pressure relationship which was employed 

 in its theoretical deduction, it furnishes an indirect proof 

 that gaseous laws are applicable to dilute solutions. 



If p be the vapour-pressure of the pure solvent at its 

 absolute boiling-point T, and p' the vapour-pressure of 



