24.6 REPORT—1899, 
Heat of Combination of Metals in the Formation of Alloys.—Report of 
the Committee, consisting of Lord KeEtyin (Chairman), Professor 
G. I’. FirzGeratp, Dr. J. H. GLapstone, Professor O. J. LopGE, 
and Dr. ALEXANDER Gat (Secretary). 
At last year’s meeting at ‘Bristol Dr. Galt submitted to Section A an 
account! of some experiments which he had made on the heat of com- 
bination of zinc and copper. The Association then granted 20/. for the 
continuance of the experiments. The work was accordingly continued by 
Dr. Galt, and the Committee have received from him the following 
account of his experiments made since the Bristol Meeting :— 
Altogether twenty-two different alloys of zinc and copper, whose com- 
position varied from 5 to 90 per cent. of copper, were made for this 
investigation from practically pure metals, and their analyses determined 
by Messrs. Johnson, Matthey, and Co., London. The first set of five, num- 
bered A, B, C, D, E, was sent on March 16, 1898 ; the second set, of 
seven, numbered 1-7, on December 1, 1898, and the third and final set 
of ten, numbered L—V, on March 8, 1899. With these alloys and with 
the corresponding mixtures of the metals, all in fine filings, the experi- 
ments were carried out. The procedure adopted was exactly similar to 
that described in detail in last year’s paper, and each experiment was | 
repeated from three to six times, until consistent results for the heat of 
solution in each case were obtained, and the mean of these was taken. 
The heat of solution of zinc alone and of copper alone was also ascertained 
in a similar manner. The total weight of the whole apparatus (excluding 
acid and metallic filings) was 42 grammes, and its water equivalent 
was found to be 5:7 grammes. The specific heat of the nitric acid used, 
density 1°360 at 15° C., was determined, and the mean of several values 
was ‘658. 
A tabular statement of results is appended. The absolute amount of 
heat evolved in dissolving 1 gramme of metal is calculated from the 
following formula :— 
H=?#{(v.g.s.) +c}, where 
¢ = increase of temperature in Centigrade degrees of the acid used 
per gramme of metal dissolved, 
» = volume of the acid in cubic centimetres, 
g = density of the acid, 
s = specific heat of the acid, 
*c = water equivalent of the apparatus. 
The specific heat of the metal used is negligible, and is not taken into 
account. 
The heat units evolved by the solution of 1 gramme of each alloy 
and of the corresponding mixture are shown on fig. 1, values for mix- 
tures being denoted by a small circle, those for alloys by a small cross. 
On the same figure are shown the results for 1 gramme of zinc alone, and 
also for | gramme of copper alone, and on joining these two points by a 
1 Brit. Assoc, Rep. 1898, pp. 787, 788. 
