384 REPORT—1883. 
the proportions given are 1 lb. of copper to 2 oz. of tin, or if required to 
be harder, 24 oz. or 24 oz., and so on; then as regards brass, it may be 
70 lbs. of copper and 30 lbs. of zinc, or 60 lbs. of copper and 30 lbs. of 
zine, or 60 lbs. of copper and 40 lbs. of zine for yellow metal, and so on. 
Now, not one of these alloys or others described are in atomic pro- 
portions, and that is the reason why unsatisfactory results are constantly 
occurring in ordinary brassfounding; not only are the copper alloys 
thus produced weak, soft, spongy, and porous, but it is a constant occur- 
rence that the constituents vary in different parts of the casting; this 
is the case principally in the gun metal and bronze alloys, the surplus 
tin above that forming a definite alloy in atomic proportions seems to be 
held in mechanical suspension, separates by liquation, and collects at the 
top of the casting as it cools and solidifies, causing the well-known tin 
spots, sponginess, &e. 
The only remedy the ordinary brassfounder has for this is to use as 
large a proportion of scrap-metal as he can get ; he does not know why, 
he only knows that he gets better castings by using it; but the true 
reason is that the scrap-metal has adjusted its constituents in atomic 
proportions during the several remeltings it has undergone, the surplus 
tin or zinc having been got rid of by liquation and oxidation; but if in 
the original manufacture of the alloy the metals are combined in atomic 
proportion, nothing of this kind happens, the castings are sound, and the 
alloys homogeneous and stable. 
In the manufacture of manganese bronze this principle is always kept 
in view, and all the different qualities produced have the metal they are 
composed of combined in atomic proportions. Whether by this any 
chemical combination is effected, it is difficult to say; but this much 
I can vouch for, that the alloys thus produced are finer in texture, more 
homogeneous, stronger, and of a very much more stable character than 
when not so combined ; thus, in the No. 3 quality the addition of + per 
cent. of tin, instead of making it harder and stronger, as it ought to be 
according to the ordinary accepted ideas, actually makes it softer and 
weaker and the grain coarser, and the same thing occurs if the additional 
tin is increased 4 or 1 per cent., until the tin arrives at another definite 
atomic proportion, when an alloy of a different character appears, but it 
then becomes again close-grained, sound, homogeneous, and stable. 
Asa further proof of the soundness of this theory, the No. 3 quality 
may be passed through an ordinary reverberatory furnace, and although 
in being thus treated it is exposed for a considerable time to the action 
of an oxidising flame, no appreciable diminution of the tin in its compo- 
sition has been detected. Then again, both the No. 1 and No. 2 may be 
remelted several times in the crucible, if it is done with care, without any 
alteration of its components. 
It is well known how difficult it is to melt brass and yellow metal, 
even in a crucible, when every precaution is taken, without some of the 
zinc escaping in fumes. This also, to a certain extent, occurs in melting 
the No. 1 and No. 2 manganese bronze; but the zinc apparently carries 
its atomic complement of copper with it, so that the proportions of what 
remains are not disturbed. I am led to this belief not only by examining 
the metals after remelting, but by the colour of the condensed fumes, 
which, instead of being white, as they are when produced from zinc alone, 
have a beautiful pink colour, which I can only attribute to the presence 
of copper. 
