towards a Dynamical Theory of Solutions. 45 



molecular architecture. With Thwing's experiments on 

 acetic acid and water the results are : — 



100;^ 30 40 50 60 625 70 74 77 80 



(K 2 -l)/p 2 ... 83 90 104 127 135 99 102 116 67 



For water (K 2 — l)/p 2 is 74*5. It appears then as though 

 in these experiments, except when ^ = 0*8, (K 2 — 1)//) 2 for 

 hydrol is larger than for dihydrol. 



Viscosity and Fluidity. 



For the adequate treatment of this subject a dynamical 

 theory of the viscosity of liquids is most desirable. Though 

 Jaeger and Brillouin among others have prepared the way 

 for such, deductive methods have not yet led to a rational 

 formula connecting the viscosity of a mixture with that of 

 its ingredients. On the experimental and empirical side it 

 has been found that a formula 



for the viscosity of a mixture is often too rough an approxi- 

 mation to the truth. Sometimes 



V/P =PlVl/Pl+2' ) 2V2/P2 



performs better, in other cases worse. Bingham has found 

 that I/77, the fluidity, can be fairly well represented by the 

 simple mixture formula 



Vv=Pi/yi+P2V2 (33) 



and leads to general relations between viscosity and chemical 

 structure (Amer. Chem. Journ. xxxv. p. 195, 1905; Ztschr. 

 f. ph. Chem. lxvi. p. 1 & p. 238, 1909). So with our abnormal 

 mixtures I shall investigate viscosity 77 through its reciprocal 

 l/?7 the fluidity. Though the viscosity of liquids is not far 

 advanced on the theoretical side, its experimental contribu- 

 tions to our subject are most helpful. Ever since Graham 

 found a maximum viscosity in mixtures of water and alcohol 

 corresponding with its maximum density, and a similar result 

 was established for mixtures of water and acetic acid, many 

 experiments have been devoted to the phenomenon, because 

 it brings out so emphatically the occurrence of rather pro- 

 found molecular re-arrangements. For instance, at 25 u C. 

 the" viscosity of water is 0*00891, of alcohol 0*01113, while 

 the maximum viscositv, when p 1 = 0*46, is 0*0*2368. 



In "'The Mol. Const. o£ Water" I have shown that the 

 viscosity of water is chiefly due to its trihydrol, having 

 estimated that at 0° C. 77 for trihydrol is 0*0381 and for 



