﻿12 Mr. W. Sutherland on the Molecular 



number o£ carriers of electricity is increased, though all travel 

 with velocities which are not exceptional. Indirectly we have 

 confirmed equation (16) of " Ionization &c." connecting ionic 

 velocities with the properties of ion and solvent. "We have 

 also confirmed the relation established in Table II. of the 

 present paper by bringing H into line with the other positive 

 ions and OH into line with the other monovalent negative 

 ions. 



4. Specific Heat. 



It has long been known that if the specific heat of an electro- 

 lytic solution is c' , that of water being c, and of solute r 4 , the 

 difference p 3 c +p±c 4 — c f is mostly positive; there is a diminution 

 of specific heat on solution. In " The Molecular Constitution 

 of Water " (loc. cit.) it was shown that the specific heat of 

 (H 2 0) 3 is of the order G'6, and that of (H 2 0) 2 about 0'8. 

 The specific heat of water is largely absorbed in changing 

 (H 2 0) 3 into (H 2 ( )) 2 . The direct action of solutes in changing 

 (H 2 0) 3 into (H 2 0) 2 is to increase the specific heat of the 

 solution above p z c + p 4 c±, because of the increase in the amount 

 of (H 2 0) 2 having a higher specific heat than the (H 2 0) 3 

 which it replaces. If this were the sole action of the solute, 

 Pz c + P4 C 4 ~~ c ' would be negative instead of generally positive 

 according to experimental evidence. Hence the chief effect 

 of the solute in making p^c -\- p 4 c 4 — c f positive is an alteration 

 of the rate of change of (H 2 0) 3 into (H 2 0) 2 with rise of 

 temperature. For the specific heat of water we have formula 

 (25) of " The Mol. Const, of Water/' 



c=p 1 c 1 +p2C 2 -t-(D + dh/dp 2 )dp 2 ldt, . . . (14) 



where D is the heat absorbed in dissociating a gramme of 

 (H 2 0) 3 into (H 2 0) 2 , and h is' the heat evolved when p x 

 of (H 2 0) 2 is mixed with p 2 of (H 2 0) 3 , and t denotes tempe- 

 rature. It is shown that 



D + rfA/^ 2 =-78-3290(0-425-p 2 ) 2 . . . (15) 



For a solution then 



c'=p d {pi / c l +p 2 'c 2 +{D + d/i/dp 2 ')dp 2 '/dt}-]-p^. . (16) 



Remembering that p 1 +p 2 = l=p 1 ' +p 2 , we get 



p z c +p±c± - c' =p 3 { (d — c 2 ) {p 2 r —p 2 ) - (D + dhldp 2 ')dp 2 '/dt 



+ (D + dh/dp 2 )dp 2 /dt\ (17) 



To fix the probable relative importance of the terms on the 

 right, let us consider the case of a solution of NaCl at 18° 



