ON THE ALLOYS OF COPPER AND ZINC. 55 
where the alloy came in contact with the ingot-mould; it was, however, exceedingly 
thin. On pouring some of the remaining alloy into a cold iron mould, a yellow film 
of the usual thickness was obtained. 
Although the phenomena of tempering exhibited by these alloys are more readily 
perceived among those the normal color of which is white, it is highly probable that ` 
all the alloys are liable to have their physical properties influenced to a greater or 
less extent from this cause. ‘This would appear, not only from the evident analogy 
of these phenomena with those which are known to occur with alloys of copper 
and tin;* but Dussaussoy f has already shown that ordinary brass, copper 65 to 
10 per cent plus zinc 30 to 35 per cent, is rendered softer, less tenacious, and less 
dense by tempering it;—a fact which Mallet f has very properly urged in explana- 
tion of the differences between several of the specific gravities of alloys of copper 
and zinc observed by himself, and the numbers which had been previously obtained 
by other experimenters. I would here suggest that it explains equally well the very 
great variations among the specific gravities of the different alloys studied by Mallet 
himselfS It is also the most probable explanation of the alloys of abnormal color 
which he has described. I should observe in this connection, that in the alloys of 
light yellow color the yellow appears to be made much deeper when the alloy is 
strongly compressed, as when cut with a cold-chisel or hammered. I may also 
incidentally mehtion, that in the series of alloys which I have prepared, a constantly 
increased degree of hardness has been observed, in proportion to the amount of 
zine contained in the alloy, — at least as far as the brittle white alloys, which are 
so hard that an ordinary file makes little or no impression upon them; || a result 
* Vid. d'Areet in Dictionnaire de l'Industrie Manufacturiére, etc, X. 500, Art. Tam-tam (Paris, 
Bailliere, 1841) ; also, Ann. Ch. et. Phys. (2. LIV. 331. See also Dussaussoy, Ann. Oh. et. Phys., (2.) 
Y. 225. 
T Loc. cit., p. 226, et Tableau No. 5. 
1 Loc. cit., p. 264. 
§ I have found it impossible to construct a curve of any regularity from the observations of this chemist, 
although it is tolerably clear that the greatest condensation is at a point somewhere below the alloy com- 
posed of equal equivalents of copper and zine, and that between this point and pure copper the specific 
gravity gradually increases with some degree of regularity in proportion as the amount of copper increases. 
. Among the observed specific gravities of the white alloys rich in zine, there is no regularity whatsoever. 
The determinations of Mallet are, nevertheless, unquestionably the best which have ever been made; 
possibly they are the best which could be made in any case. At all events, few chemists are in the posi- 
tion to improve upon the method of preparing alloys which was employed by this distinguished observer. 
| From this category the alloys modified by tempering must of course be excepted. 
