90. - ON THE ALLOYS OF COPPER AND ZINC, 
for their quantitative analysis, by heating the sample of alloy in a porcelain tube, 
through which a current of hydrogen is made to flow. 
In preparing the alloys, it may readily happen, if the mass be not very frequently 
stirred, that a small portion of the copper, or of an alloy rich in copper, may become 
chilled and solidify at the bottom of the crucible, while a quantity of easily fusible 
alloy, rich in zinc, has formed and remains liquid above it. Accidents of this 
nature happened to myself very frequently during the earlier part of the research. : 
They occasioned no inconsiderable loss of time, since it was in every instance 
necessary to prepare a new sample of the alloy on account of the enormous waste 
of zinc which would occur if one attempted to remelt the chilled culot; and were 
especially vexatious, from seeming to indicate the existence of definite alloys having 
little or no affinity for each other. Similar accidents sometimes occur in brass- 
founderies, but are evidently less liable to take place here, where the amount of 
melted metal is large and the heat well regulated, than in the small crucibles and 
furnaces of the chemical laboratory. It is worthy of remark, that many brass- 
founders refer them to some peculiarity of the particular sample of copper used. 
If any trouble of this kind is experienced, a portion of common salt is usually 
thrown into the crucible, it being regarded as a remedy. It is very probable that 
the presence of some foreign metal may prevent or retard combination; on the 
other hand, copper which still contains a portion of sulphur is thought to combine 
with zinc with peculiar facility. In my own experiments these occurrences appeared 
to depend entirely upon irregular heating of the furnace, or upon insufficient stirring. 
D. Forbes* has analyzed such specimens which were produced accidentally in the 
ordinary process of brass-making. They consisted of a white alloy containing 
46.51 per cent of copper, and of a yellow alloy containing 56.91 per cent of copper. 
From my own experience, I am satisfied that layers containing almost any proportion 
of the two metals may form. | 
It is doubtless this tendency of the metals to remain unmixed in, separate layers, 
when not subjected to agitation, which has led several chemists to believe that the 
alloys of copper and zinc are apt to separate by eliquation into two portions re- 
spectively rich in copper and in zinc; from which they have inferred, as I have 
previously remarked, the existence of definite compounds. Although in my own 
experiments I have been unable to detect any eliquation, I would by no means 
* Report of 24th (Liverpool) Meeting of the British Association for Advancement of Science, 1854, p. 67. 
See also Liebig and Kopp's Jahresbericht. 
