54 ON THE ALLOYS OF COPPER AND ZINC. 
frequently observed, upon the under surface of the sheet obtained by pouring off 
the liquid alloy, a thin layer of a soft, tenacious, malleable alloy, of a yellow color. 
The formation of this singular sheet was at first attributed to eliquation; but as it 
was difficult to conceive that an alloy apparently richer in copper should remain at 
the surface of the melted mass in the crucible, — which must have been the case 
in order that it should form the bottom of the ingot, — it was thought possible 
that volatilization of the zinc might have increased the proportion of copper at the 
surface of the melted alloy. In order to decide this question, a new series of alloys 
was prepared, extending from the one obtained by melting together 40 parts of- 
copper plus 60 parts of zinc, to the mixture of 56 parts of copper and 44 parts 
of zinc;— each alloy being made from a mixture containing one per cent more 
copper than that used in preparing the preceding. After thorough stirring, the 
alloys were cast into ingots of about five pounds’ weight. In the first four of ` 
these alloys — from 40 to 44 per cent of copper — the yellow film was very clearly 
defined on the three sides of the ingot which had come in contact with the metal 
of the mould, while on the upper surface of the ingot, which had cooled in contact 
with the air, no trace of it could be detected. This yellow film is usually of extreme 
tenuity, hardly exceeding one sixteenth of an inch in thickness in any of the instances 
which I have observed. It is, however, so very clearly defined in the white alloys 
containing 40 to 45 per cent of copper, being readily bent, cut, or filed, while the 
remainder of the alloy is exceedingly hard and brittle, that no question as to its 
identity can possibly be entertained. In the alloys containing more than 50 per 
cent of copper, which are naturally of a yellow color, it is not so easy to detect a ` 
similar film. In the series of ingots just mentioned, it could nevertheless be traced 
as far up as the alloy prepared from 54 parts of copper plus 46 parts of zinc. 
An experiment made in order to ascertain whether this soft modification of the 
alloys could be obtained at will, afforded no positive result. An alloy of 42 parts 
of copper plus 58 parts of zinc being prepared, a portion of it was poured by 
small drops into a large mass of cold water. The surfaces of many of the granules 
thus obtained were covered with a yellow film, and this was especially true of the 
smallest pieces; but the film was exceedingly thin, and the interior of the granules 
consisted entirely of brittle white alloy. Other portions were thrown out upon 
cold iron plates, so as to form very thin sheets. A thin yellow film occurred, it - 
is true, upon the inferior surfaces of these sheets, but above it the alloy was white 
and brittle. Another portion of the melted alloy was cast in an iron ingot-mould 
which had previously been heated “black-hot.” The yellow film was still formed 
