ON THE ALLOYS OF COPPER AND ZINC. 51 
assert that a certain amount of such.separation may not under some circumstances 
occur. The method of analysis which I have adopted is not delicate enough, nor 
will the very conditions of the case itself admit of an accurate determination of this 
point. My results are, however, as I think, sufficient to show that any tendency 
towards eliquation which may exist must be very slight, although they do not 
prove that a small amount of it may not be produced by gravity, or by some other 
force acting against the comparatively feeble affinity of the metals for each other. 
Experiments upon this subject which have been recorded by previous observers have 
evidently been exposed either to the error of insufficient mixing in the first instance, 
or to the loss of zinc by volatilization from those portions of the alloy which were 
in contact with the air, or to both of these causes. Some of them appear to have 
also been influenced by the presence of foreign metals in the alloy. 
The most contradictory statements have been made by different observers in 
regard to variations of color among the alloys of copper and zinc. In the speci- 
mens which I have myself prepared, no abrupt change, or peculiar modification, of 
the true color is to be perceived, although some very striking superficial characters 
present themselves. Starting from the red of pure copper, the color of the alloys 
is less red and more yellow in proportion as they contain more zinc, until an alloy 
containing 75 or 80 per cent of copper is reached, the color of which is almost 
pure yellow; beyond this point, as the proportion of zinc contained in them is 
increased, the alloys become less yellow, with perhaps a tinge of green, and more 
white continually, and this by the most gradual stages, until the well-known 
white alloys are reached. 'These remarks refer to the color of polished surfaces, 
as obtained by the use of a fine file. Each of the alloys enumerated in the list 
upon page 42 having been carefully compared with the chromatic scales of Digeon.* 
In several of the alloys, especially in those containing about equal parts of copper 
and zinc, a beautiful yellow or sometimes gray iridescent film forms upon the surface 
of the metal during the process of cooling. On fracturing it, moreover, the fibres of 
which the mass is formed present the same yellowish or grayish iridescence. This 
is removed at once by filing, when the true color of the alloy is made manifest, as 
has already been observed by Guettier} in regard to hard-solder. With the exception 
of Guettier, most modern observers have described this alloy, prepared by fusing 
* Cercles Chromatiques de M. E. Chevreul, reproduits au Moyen de la Chromocalcographie, par R. H. 
Digeon, Paris, 1855. Chez Digeon, Rue Galande, No. 65. 
t Loc. cit., S. 207. 
