50 Mr. W. Sutherland on Weak Electrolytes and 



formulae with the mean specific heat of water between 22° 

 and 98° taken as unity : — 



c = 0-6628 + 0-7945 J p 2 -0'45^ 2 2 from p 2 =.0 to 0*5 . . (39) 



= 0-9475 + 0-5164(p 2 -0-5)-0-625(p 2 -0-5) 2 



from jt? 2 = 0'5 to 0*8 . (40) 



= l*0455-0*104(^-0*7991)-0*482( / > 2 -0-7991) 2 



from p 2 = 0'S to 1-0 . (41) 



From these we derive the following values of c— p\Ci— p 2 c 2 

 the increase of specific heat on mixing, with ^^Q'6628 and 

 r 2 = l, namely 



0*4573p 2 — 0*45jtv or nearly m 4:5Spip 2 from p 2 = to 0*5 

 0-446^ 1 ^ 2 -0'179 j p 1 2 + 0-049 from ^ 2 = 0*5 to 0'8 



0-482^72 + 0-153^ +0-005 from p 2 = 0'S to 1-0 



It will be noticed that in each case the most important 

 term is nearly 0'45pijt? 2 , a result which, by itself, would 

 make it appear that there is only one main process in the 

 reaction between alcohol and water. At the limit when p 2 

 is small we have 



(c —pxCi —p 2 C2)/p2 = 0'458pi = 0-458. 



But if in this case p 2 water is changed into p 2 hydrol of 

 specific heat c 2 , we can write the last expression 



(c -p^j —p 2 c 2 -p 2 c 2 +p 2 c 2 ')/p 2 , 



in which, by the simple mixture formula, 



c—-pici—p 2 c s ' = 0, 



so that the expression becomes 



c 2 '-c 2 = 0-458, and c 2 ' = l'458. 



But at the Faraday Society's discussion I found 0*513 to 

 be the average specific heat of solid hydrol as water of 

 crystallization. It appears then that c 2 is only hypo- 

 thetieally a specific heat of hydrol to which the simple 

 mixture formula applies, that it includes both the specific 

 heat of hydrol and the rate of change of its heat of solution 

 in alcohol with temperature. At the other limit when p 1 is 

 small and p 2 nearly 1, 



(c —'piCi —p2C 2 )/p 2 = 0*635^ + 0-005 (1 + p{), 



where the difference between 0'640 and 0*458 indicates a 

 certain difference between the reactions at the two limits, 

 but not a very pronounced one. The specific heat of dihydrol 



