1897 - 98 .] Dr A. Galt on Heat of Combination of Metals. 139 
With regard to the metals, no difficulty was experienced in dis- 
solving the brass and the zinc ; indeed the chemical action when 
the latter was being dissolved was rather violent, and the evolution 
of fumes was so rapid that in the early experiments considerable 
trouble was experienced in the efforts to control the fumes and 
prevent their escape and consequent loss of heat. On the other 
hand the free copper dissolved more slowly, otherwise a more 
dilute nitric acid than that mentioned would have been used. As 
it was, it was found necessary to have the copper always in the 
state of fine filings, prepared by the somewhat laborious process of 
filing down from the sample by means of a very fine file. The 
brass and the zinc were also used in the form of filings, much 
coarser than those of the copper. In all cases the filings of the 
separate elements were made from the same pieces which had been 
partly used in making the alloy. 
The first experiments were made on a sample of ordinary brass, 
and I am indebted to the kindness of Mr W. R. Lang, B.Sc., and 
of Mr Carrick Anderson, M.A., B.Sc., of the Chemical Depart- 
ment of the University, for a quantitative analysis not only of this 
specimen but of others, metals and alloys, used in the course of 
this investigation. It was always necessary to know the composi- 
tion of the alloy used, so that a convenient quantity of the mixed 
metals, in the proportions in which they exist in the brass, could 
be weighed out for solution, and a fair comparison made between 
the heat of solution of this quantity of the alloy and of the same 
weight of the mixed metals. The brass was found to contain 
64 per cent, of copper, 32 per cent, of zinc, and 4 per cent, 
of lead. 
The experiments were only partially satisfactory, as a residue 
was always obtained which took a considerable time to dissolve. 
It was small in amount, and was doubtless due to the lead. How- 
ever, the experiments clearly showed that the heat of solution of 
the alloy was less than the heat of solution of the mixture. To 
eliminate the disturbing influence of the lead, a sample of brass 
was specially and most carefully made, from the best commercial 
zinc and copper, by Mr MThail, brassfounder, Cambridge Street, 
Glasgow. Its composition was about 52 per cent, copper and 48 
per cent. zinc. 
