106 ROYAL SOCIETY OF CANADA 
When the following solutions were made, the change in temperature 
A 7 Was observed: — 
NIET 
32 grams Methyl Alcohol in 100 grams water ............ .... ..... + 8:50° 
46 ‘ Ethyl fF £ A nie Ce ES + 8'30° 
60. n-Propyli se DE CERCLE LUE . + 4:00° 
58) *S" Acetone’ (<5 £8 SF + ONE LT SCORE + 7:60° 
92 ‘“ Glycerine ‘ 4 Fe Oe ePIC ED Acc + 470 
100 c.c. Toluene in LOU cic Benzenomeeeerrtiis.. re coe mere — 037° 
Equal volumes of Acetic Ether and Benzene ........................ — 0°55° 
x . olen e ciated Se ae eee =, (HET 
‘ Aceto Acetic Ether and Benzene..... ............ — 1:00° 
4 Loluene :::- 00m — 1:00° 
os Quinoline andiBenzenes ass.) oso Ce ee eee — 010° 
The first five are mixtures of an associated liquid with an asso- 
ciated solvent and the heat change is a large one. In the remainder 
the liquids are both non-associated and the heat change is small. It 
is also of opposite sign. These results seem to point to the con- 
clusion that the main source of the thermal effect in the solution of 
such substances is due to the dissociation of molecular aggregates 
and this was confirmed by a few more roughly qualitative experiments 
in which the mixing was done in a test tube using 5 c.c. of each 
liquid at the same temperature. 
Methyl Alcohol and Ethyl Alcohol................ ...... A T= + 065 
+ Wer Usk LOPVIPALCOMO arte 2. AE - 0°37 
Ethyl Alconol ‘“ ns SO OSS a eRe farcical + 0°8° 
Benzene and Ethyl Alcohol................ 48 bOI) AAR — 57° 
Toluene ‘‘ HE An as dessus Mer à — 5'2° 
m-Xylene and DANONE bSc od ao te oO REECE Eee — 4°5° 
Benzene and n-propyl Alcohol....:.......,............. — 30° 
Acetic ether and Ethyl AICGROI .. ose Le ees aes — 72 
There is, therefore, a very small heat effect on mixing the alcohols 
with each other — à result quite in accord with the idea of association. 
For being so similar in nature and in degree of molecular complexity 
any influence which the methyl alcohol might be expected to have 
in breaking down the aggregates of ethyl alcohol would apply equally 
to its own aggregates. A very remarkable fact, however, is that, 
whereas all mixtures of water and the various alcohols with each 
other give out heat, in every other case that has been examined the 
heat change is negative. The above values show also that the amount 
of heat absorbed during the solution of an associated liquid in an 
unassociated solvent is by no means inconsiderable, while, when both 
liquids are unassociated it is insignificant. A few experiments per- 
formed very recently do not show the same agreement, however, with 
this theory of the cause of the phenomenon. When acetone is dis- 
solved in acetic ether there is very little heat change, yet acetone is 
