58 Mr. W. Sutherland on Weak Electrolytes and 



found the results consistent with the idea that when p x is 

 less than 0*5 alcohol changes the trihydrol of water into 

 dihydrol, and when p x is greater than 05, dihydrol is changed 

 into hydrol, which in the experiments of Abegg has a 

 dielectric capacity equal to that of dihydrol, in those of 

 Nernst less and in those of Thwing still less. In the solid 

 hydrol of water of crystallization K is much less again, being 

 of the order of magnitude of 6. In Thwing's experiments 

 with acetic acid and w T ater K for hydrol and (K — 1)1 p appear 

 to be larger than for dihydrol. Here again we have evidence 

 that the properties of hydrol are very variable with environ- 

 ment. From the study of fluidity we get good evidence of 

 molecular changes, probably two main changes, but the 

 alterations of fluidity involve changes of the mutual relations 

 of unlike molecules in contact as well as changes of indi- 

 vidual properties caused by change of molecular constitution. 

 A kinetic theory of! the viscosity is needed for interpreting 

 the experimental results definitely. 



In interpreting the change of: specific heat on mixing we 

 encounter the same difficulty, that there are changes of 

 mutual relation as well as of individual property. In 

 mixtures of alcohol and water the change of specific heat 

 occurs nearly as if it were caused by only a single molecular 

 change, (c— piC\— p<fi)lp^ at 60° 0., ranging nearly from 

 O'QIO jh to 0-458^! as p 1 passes from to 1. At 0° the 

 corresponding range is from 0'78 pi to 0'33p b this contrast 

 supplying evidence that probably here there are two main 

 molecular changes really occurring. With the heat H 

 evolved on making a gramme of mixture it is found that 

 H/pip 2 tends to two different limits 70 and 20 when pi = 

 and 1. From the specific heats of mixtures of water with 

 the fatty acids no definite conclusions are drawn. The 

 surface energy of mixtures is investigated from the point of 

 view that the surface of water below 40° 0. consists of tri- 

 hydrol and the surface of a mixture of trihydrol and the 

 other ingredient in different proportions from those of the 

 bulk. Simple relations are thus obtained for pu/pi, but 

 the results do not bear directly on our problems of the 

 molecular constitution of the mixture in the bulk. 



It is fairly well established that at ordinary temperatures 

 the liquid alcohols and fatty acids have molecules double 

 of those represented by their usual chemical formulas. 

 Throughout the present discussion it has been assumed that 

 on mixing with water these molecules are unchanged, the 

 ionization of the fatty acids having a negligible effect on 



