30 ON THE ALLOYS OF COPPER AND ZINC. 
regular system, as well as upon the fact, which will appear in the sequel, that 
none of the crystals have been found to contain any larger quantity of either of 
their component metals than was contained in the remainder of the molten liquid 
from which they had separated, I have based my conclusion that the alloys of 
copper and zinc are isomorphous mixtures * of the two metals. 
On this hypothesis it is of course presumed that both copper and zine are capable 
of crystallizing in the regular system. Copper, as is well known, always occurs in 
forms of the monometric system. But in regard to zinc this has not been so satisfac- 
torily proved. Not only, however, does analogy indicate that zinc should be mono- 
metric, — for, so far as is known, all the metals of the Three Series of Cooke t 
allied to it crystallize in forms of this system, — but Nicklés f has actually observed 
an instance in which it occurred in the form of pentagonal dodecahedrons. 
I am well aware that this is an isolated example; that the angles of the crystals 
were not measured. It is not to be supposed, however, that a chemist so well versed ` 
in crystallography as M. Nicklés could have been mistaken regarding the form of 
his specimen. We know, moreover, from the analyses of Favre,§ that the zinc was 
almost absolutely pure. Gustav Rose|| has urged against this observation, that the 
form of the crystals is an improbable one, since no other instance is known of a metal 
crystallized in pentagonal dodecahedrons. I cannot myself perceive the force of this 
argument; few facts are more thoroughly established, than that the crystalline form 
of bodies may be largely modified by the influence of the circumstances under which 
they are formed, — witness, for example, the crystals of common salt obtained from 
solutions containing organic matter,€8| — while almost all the crystals of metals with 
which we are acquainted have been prepared by a single process, — igneous fusion. 
Rose has also maintained that the crystals of Nicklés are similar to the rounded 
or irregularly crystallized masses formed in an atmosphere of zinc vapor which he 
* It must not be supposed that this view supports in the least the idea of the older chemists, that alloys 
were mere “mixtures” of their component metals. For the experiments of Karsten (loc. cit., S. 398, 400) 
have already shown that the comportment of the alloys of copper and zine towards acids, and the solutions 
of various metallic salts, is that of chemical compounds, being entirely unlike that of a simple mechanical 
mixture of the two metals, or of a mixture of several alloys. 
— t Memoirs of American Academy, (New Series) V. table to p. 256. 
i Ann. Ch. et. Phys, (3.) XXII. 37. ; 
$ Ibid., X. 170. 
| J. pr. Chem. (N. F.) LV. 292. 
Y Vid. Robin et Verdeil, Traité de Chimie Anatomique, (Paris, 1853,) II. 198, et Atlas, pl. 1. 
