Forces between Atoms and Chemical Affinity. 779 



Solvent. 



K. 



v. 



H,0 



80 



40 



39 



36 



36 



325 



27-2 



26 



17-9 



167 



32 



200 



200 



320 



270 



400 



800 



1000 



2000 



3200 



CH.3NO, 



C-H 4 o ..... 



CHjCJST 



CH 3 SCN 



CH3OH 



C.,H-CN 



C-H s o 



C^HuOg 



C.H-CH CN 





when it emerges is mixed with positive and negative ions ; 

 little if any electrification, however, is found when the gas 

 bubbles through a liquid like paraffin oil or benzene where 

 the atoms in the molecule are not charged. This is shown 

 very clearly by the recent experiments of M. Bloch, Annalen 

 de CMm. et de Physique, xxiii. p. 28 (1911). 



We could account for this difference in the following way. 

 When the gas bubbles through the liquid fresh liquid surfaces 

 .are continually being produced; these surfaces have an amount 

 of energy equal per unit area to the surface tension. Since 

 this energy tends to a minimum, the effect of the action 

 between the molecules which produces surface tension will 

 be to promote any change which diminishes the surface 

 tension at the fresh surface. For example, if any chemical 

 .action will diminish the surface tension, that action will take 

 place more readily at the fresh surface than in the body of 

 the liquid. If the liquid is a salt solution, the salts will flock 

 to the surface if the surface tension of a strong solution is 

 less than that of a weak one and recede from it if it is greater. 

 If two isomeric compounds have different surface tensions, 

 then spraying or bubbling air through a mixture will in- 

 crease the proportion of the one with the smaller surface 

 tension. The molecules of a compound AB might split up 

 at the surface layer into atoms, if a layer of dissociated atoms 

 either mixed together or in separate layers would give a 

 smaller surface tension than the undissociated liquid. 



We see from this that the causes which produce surface 

 tension might dissociate the molecules of the liquid at the 

 surface of the cavities formed by the bubbling of the gas 

 through the liquid. If the liquid were of the type in which 



