ON THE ALLOYS OF COPPER AND ZINC. 49 
the various impure ores of copper, I cannot here speak. Many of them have been 
already described by Kerl* I would, however, mention the fact, that, in cases 
where arsenic is the only impurity, it has been found advantageous in practice to 
precipitate it upon iron with the copper, and to expel it subsequently when the 
latter is heated in the atmosphere of hydrogen. 
It is a well-known fact, that the combination of copper with zinc is attended 
with ebullition of considerable violence, so that portions of the melted mass are often 
thrown to a distance of several feet from the crucible. Yet it does not appear to 
have been previously noticed by chemists, that this action is much more energetic 
while the first portions of zinc are being added to the copper, and that the loss of 
zinc by volatilization is far greater at this time than at any subsequent stage of the 
operation ; indeed, when the alloy has become somewhat rich in zinc, it takes up an 
additional portion so quietly, that scarcely any action is to be observed. The fact 
is, however, well known to brass-founders, who are in the habit of first melting a 
quantity of old brass with the copper in their crucibles before adding any zinc 
as such. 
A very violent action will also occur, if, after allowing the zinc to melt and remain 
floating above the copper, as it will do if the mass is not agitated after each addition 
of zinc, the two metals are suddenly stirred together. This action is apparently 
analogous to that observed by Levol,t which occurs when layers of melted silver 
and gold are mixed.  Levol ascribes the violent ebullition which ensues when these 
metals are stirred together to the escape of oxygen which had been absorbed by the 
molten silver, and which would be expelled as soon as this metal unites with the 
gold. This hypothesis, however, does not in my opinion satisfactorily explain the 
phenomena which occur in the case of copper and zinc. Another explanation is 
afforded by the experiments of Person, who has shown that in the formation of 
certain alloys a large amount of latent heat is evolved. 
The apparent energy with which the combination of copper and zinc occurs, is 
often mentioned in treatises on chemistry, as if it indicated the existence of strong 
chemical affinity between the two metals. Yet it is easy to separate the zinc com- 
pletely from any of these alloys by heat. Indeed, Bobierre$ has devised a method 
* Op. cit, S. 219. 
+ Ann. Ch. et Phys, (3.) XXXIX. 168. 
1 Ibid, XXIV. 146. ; 
$ Thèses, p. 57; also, Compt. Rend., XXXVI. 224. 
VOL. VIII. 4 
