OF THE ALLOYS OF COPFER AND ZINC. 
531 
In order to remove the oil, which the latter always contain, they were washed in 
carbon bisulphide, ether, and absolute alcohol, and were then dried at 90° C. 
It was hoped that a considerable range of alloys would be covered by these 
materials, as their colours varied greatly from reddish-yellow to pale yellow ; hut 
analysis showed that none contained less than 67 or more than 87 per cent, of copper, 
and it was finally concluded that they were mixtures of various alloys. 
Throughout this investigation it was found absolutely necessary to use the metals 
in a state of very fine division in order that the time occupied by their dissolution 
might be kept within reasonable limits. 
Those alloys which contained between 20 and 40 per cent, of copper were easily 
shattered by a few heavy blows in a steel mortar, and the rough powder obtained was 
then o-round in an agate mortar. 
The remaining alloys were not sufficiently brittle to be thus treated, and the tedious 
process of reducing them to j^owder with a very fine file was employed. 
These filings were then sifted through the finest linen, and only the small fraction 
which passed was used. 
This powder was then thoroughly stirred with a magnet to remove any fragments 
of iron which might have come from the file. 
In almost every case the latter precaution was found to be unnecessary. 
It has been objected that the fragments of a crushed alloy, having been strained, 
possess more energy than before crushing, and that this may affect the heat of disso¬ 
lution. (‘Report on the Chemical Compounds contained in Alloys,’ Brit. Assoc., 
1900.) 
In various experiments the author has employed a particidar alloy, sometimes in 
the form of rolled sheet and sometimes as filings, or, if sufficiently brittle, then either 
as a finely crushed powder or as filings, and in no instance has any difference of the 
nature sugo-ested above become evident. 
Choice of Solvent. 
Those solvents which most readily suggest themselves are chlorine-water, bromine- 
water, and nitric acid. 
The first and second are not only disagreeable to work with but are also Ineftective, 
unless the metal to be dissolved is in a state of extremely fine division. This neces¬ 
sarily limits their application to the small group of very brittle alloys. A number of 
experiments were performed with chlorine-water as solvent. 
Turning now to nitric acid. Dr. Gladstone"^' has quite recently shown that the 
chemical action of a mere mixture of copper and zinc upon it is difterent from that of 
the alloy containing the metals in the same proportion. 
* ‘Phil. Mag.,’ vol. 50, p. 231. 
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