36 Mr. W. Sutherland on Weak Electrolytes and 



presence of doublets acting as chemical bonds. These 

 doublets have an electric moment whose relation to the elec- 

 tric moment causing cohesion must be considered. In 

 various papers on molecular attraction I have traced cohesion 

 to the electrization o£ atoms, an atom being regarded as a 

 sphere electrized in the same way as the earth is magnetized. 

 It has an electric moment derived from the summation of 

 the electric moments of the pairs of electrons #[? out of which 

 it is formed. According to the principle of minimum poten- 

 tial energy the axes of electrization of molecules adjust 

 themselves so that the direction of the axis of a molecule is 

 the same as that of its two axial neighbours and opposite to 

 that of its four lateral neighbours . Each molecule attracts 

 its six nearest neighbours, its alternate attraction and repul- 

 sion on remoter molecules being negligible in comparison 

 with this concerted attraction on the six nearest neighbours. 

 The attraction between two neighbour molecules is propor- 

 tional to the product of their electric moments and inversely 

 as the fourth power of the distance between their centres. 

 It follows then that the electric moment of these doublets 

 which act as special chemical bonds must modify cohesion, 

 It is well known that associative liquids like water and ethyl 

 alcohol are more cohesive than would be expected by analogy 

 with the non-associative liquids, whence many of their excep- 

 tional properties. But in the case of water the cohesion is 

 not increased nearly so much as we might be led to expect 

 from the contrast between K of the order 80 and ri 2 of the 

 order 2. The reason for this is again the fact that the 

 special doublets acting as chemical bonds are subject to 

 special constraint. The constitutive electron pairs in H 2 

 swing their axes round so that each molecule attracts its 

 six nearest neighbours, but the three doublets in (H 2 0) 3 and 

 the two in (H 2 0) 2 are not free to swing into position for 

 attraction so quickly. They tend to do so where possible. 

 Tims they increase cohesion, but not to the extent to be 

 expected from the contrast between K and n 2 . From these 

 considerations it appears that the study of dielectric capacity 

 in these mixtures is imperative if we are to understand the 

 part played by atomic and molecular fields of electric force 

 in determining the properties of our mixtures and the whole 

 theory of solutions. For the normal dielectric capacity K 

 which is equal to ?i 2 , I have sought to show the dependence 

 on electric moments in atoms (" The Fundamental Constant 

 of Atomic Vibration and the Nature of Dielectric Capacity, '■' 

 Phil. Mag. [6] xix, p. 1, 1910). We shall now investigate' as 

 due to special electric moments in molecules those large 



