142 
Proceedings of Boyal Society of Edinburgh. [sess. 
Heat of Solution of *5 gramme (’26 gramme Copper + '24 gramme 
Zinc) of the Mixed Metals and of *5 gramme of the Alloy. 
Mixture. 
Alloy. 
Temperature of the Acid before and 
Temperature of the Acid before and 
after Solution. 
alter Solution. 
Before. 
After. 
Difference. 
Before. 
After. 
Difference. 
C.° 
C.° 
C.° 
C.° 
C.° 
C.° 
9-05 
17-85 
8-80 
9-60 
17-70 
8-10 
9-30 
18-08 
8-78 
9-65 
17-77 
8-12 
9*35 
18T5 
8-80 
10-20 
18-30 
8-10 
9*22 
18-01 
8-79 
9-97 
18-05 
8-08 
Mean Difference, . 
8-792 
Mean Difference, . 
8-10 
The increase of temperature of the solution of the mixed metals 
( per gramme of metal) was therefore greater than the increase of 
temperature of the solution of the brass by 2(8'792 - S’lO), that is, 
L384° C. ; and the heat of combination of any quantity of copper 
and zinc in the proportions stated (52 per cent, copper, 48 per cent, 
zinc), expressed as a fraction of the heat developed by the solution 
of the same quantity of the mixed metals in like proportions in 
nitric acid, is 
1-384 1 
2 x8-792 ”12-7 ’ 
The absolute amount of heat evolved by the combination of *52 
gramme of copper with *48 gramme of zinc was approximately ascer- 
tained as follows : — 
Let H represent, in (gramme-water) heat units Centigrade, the 
heat of solution of 1 gramme of metal, 
in cubic centimetres, the quantity of acid used, 
the density of the acid at 15° C. 
the specific heat of the acid, 
in grammes, the weight of metal dissolved, 
the water equivalent of the glass and cork of 
the apparatus. 
in degrees C., the mean difference of tempera- 
ture before and after solution. 
„ P 
