PHYSICAL CHAEACTEES OF MIXTUEES AND SOLUTIONS. 
343 
To raise 5 grms. of the mixture from 17°295 C. to 71°T5 requires 278-86 units. 
,, 4-5 grms. water through same interval . . . 242'35 
„ 0-5 grm. alcohol „ „ ... 1G-27 
Total for constituents separately .... 258"62 258-62 „ 
Difference between mixture and constituents .... 20‘24 ,, 
In the formation of 5 grms. of a 30 per cent, mixture are evolved, at a temperature of 
17*337 C., 47-98 units. 
52-3 C., 22-16 „ 
70-9 C., 10-34 „ 
To raise 5 grms. of this mixture from 
17-337 to 52-30 requires 179-36 units, 
17-337 to 70-90 „ 274*79 „ 
° ° 
To raise 3-5 grms. water from 17*337 to 53-30 requires 
„ l - 5 grm. alcohol ,, ,, 
Total units required to raise constituents 
To raise 3*5 grms. water from 17*337 to 70*90 requires 
,, T5 grm. alcohol ,, ,, 
Total units required to raise constituents 
47*98— 22 -16 =25 *82 = difference in units of heat evolved. 
179-36 — 153*99 = 25*37 = ,, „ required. 
47*98 — 10-34 = 37-64= „ ., evolved. 
274-79 — 236-02 = 38-77= „ „ required. 
The differences between theory and experiment are, therefore, in the above cases at 
least, extremely small and quite within the limits of almost unavoidable experimental 
error. 
The number of units of heat evolved during the mixing of ethylic alcohol and water 
becomes therefore less the higher the temperature at which the mixing takes place. 
Assuming, then, that the above given formula (No. 1) is correct, it is easy to calculate a 
temperature at which the mixing of alcohol and water would not he accompanied by 
evolution of heat. U' becomes zero when V = : . S(i' — t)~{x . — t)-\-y . S"(f — t)}. 
Let U be the units of heat evolved in the formation of 5 grms. of mixture at the 
temperature t , then the temperature T, at which no heat is evolved on mixing, will be 
T= r 
t>S — (a’S' + y S") ‘ * 
On making this calculation for the various mixtures examined, this temperature was 
found to he 88°-2, 87°-6, 83°-5, 88°-3, 86°, 84°-9, 78°-4, 92°, and 129°-6 C. for mixtures of 
122-37 units. 
31-62 „ 
153-99 
187-47 
48-55 
236-02 
