704 



On the Molecular Theory of Solution. 



although the order of solubility in each liquid is the same, 

 no general law is evident by which the actual solubilities are 

 determined. Consideration of molecular cohesion and 

 adhesion immediately throws much light on the relations. 



Bingham has advanced evidence in confirmation of the 

 hypothesis that the critical pressure is a measure of molecular 

 attraction at the corresponding temperature, since this 

 attraction is just balanced by the repellant forces due to 

 kinetic energy. The critical pressure in each gas is given in 

 the table as well as the corresponding temperature. 





Solubility. 



Critical | Critical 



Gas. 



Water. 



Alcohol. 



Pressure. Temperature. 



i 

 i 



Sulphur dioxide 



4356 

 3-233 

 0778 

 1-002 

 00243 

 0-03 

 00145 

 00193 



144-55 78-9 1554 

 9-54 88-7 100 

 3268 75-0 35-4 

 3 2 73 31-2 



Sulphuretted hydrogen 





Carbon monoxide 



0-2044 

 0-284 

 0-1214 

 0-0673 



1 

 35-9 -1411 



500 -113-0 



350 j-146 



14-0 -240-8 









Since the molecular cohesion of gases is less than that of 

 either solvent, their solubility should be the greater, the 

 greater their molecular cohesion, and the less the cohesion of 

 the solvent. Therefore gases should be more soluble in alcohol 

 than in water. Moreover, since the value of the factor M w , 

 corresponding to the solvent, in the second term of (3), 

 is much greater than that corresponding to the attraction of 

 the solute, the difference in the solubilities in the two liquids 

 should increase as the molecular cohesion of the gas grows 

 less. These deductions are well borne out by the figures in 

 the table. It is fair to assume that the molecular attractions 

 of the gases are affected by the temperature of observation. 



That the solubility of a gas increases as the cohesion of 

 solvent diminishes is substantiated by OhristofFs experi- 

 ments on carbon monoxide [1906]. He determined the 

 solubility of this gas in water, aniline, nitrobenzene, benzene, 

 toluene, chloroform, ethyl alcohol and acetic acid, and found 

 that the solubility of the gas increased as the surface tension 

 of the solvent diminished. 



