52 Mr. W. Sutherland on Weak Electrolytes and 



reactions of alcohol upon water. I find with the data of 

 Winkelmann that the following empirical relation takes the 

 place of the simpler one of Dupre and Page : 



H = 95(c— pic 1 -p 2 c 2 ) -5(p-pipi~P2p2) - • (43) 



For the first four fatty acids the data for c and H were 

 obtained by Ltideking (Wied. Ann. xxvii. p. 12, 1886), 

 c between 50° C. and 20°. Ignoring some marked pecu- 

 liarities at certain values of p Y , we can summarise the 

 experimental results for c in the following statement : — 



Acid. C —P\ C \—P2 C 2 from £>,= to p i = 



Formic 0-0569 ■ " 0-836 0-836 



00297 719 719 



-003^ 2 0-630 389 



-007 p x p 2 0-338 0-242 



-{0-07 +0-8(0-242-^)}^^ 0-242 0-0 



Acetic -0-0074 0869 0-869 



0-0S Pl p, 0-769 0625 



0-12p.pl 0-526 0-250 



{0-124-6-7(0-25-^ 1 )J^ 1 ^ 2 0-250 0-0 



Propionic 0-16 0"891 0'891 



0-25 p lP2 804 0-406 



{0-25 +0-2(0-406 -Py^p.v, 0406 



Butyric -| 035 -0-4(0-907-^)1-^^ 0-907 0379 



{0-15+0-2(0-379-^ 1 )}^ 1 ^ 2 0-379 0-0 



Formic acid stands apart from the others by having 

 c— PiCi~ P<2 C 2 negative except for the two highest values of 

 ■p x where it assumes a large positive value. In all other 

 cases e—p\Ci — p 2 c 2 is positive except at the highest value of 

 p x for acetic acid. The distinction between formic and the 

 other acids recalls the fact that A is smaller for formic acid 

 than the others. The limit of (c - p 1 c 1 —p 2 c 2 )/p 1 p 2 for small 

 values of p 2 is not obtainable from these experiments. When 

 jt? 2 = l it seems to be about —0*26 for formic, 0*3 for acetic, 0'3 

 for propionic, and 0*2 for butyric acid. These limits indicate 

 similar reactions for the three latter acids upon an excess of 

 water. The facts all point to more than one action, but the 

 conditions are so complicated that it is not possible at present 

 to demonstrate two main processes, that of change of trihydrol 

 into dihydrol and that of change of dihydrol into hydrol. 

 The chief complication is the heats of solution of the varying 

 amounts of hydrol, di- and trihydrol in the different acids. 



The values of H run characteristic courses with the four 

 acids. With formic acid H. is positive except for a small 

 region of pi near 0*1 and attains a maximum value of 2 14 



