62 
MESSRS. C. T. HEYCOCK AND P. H. NEVILLE ON 
freezing point jufst reached, and that solid is beginning to form, as it must, from 
both conjugates at once* The separation of this solid will cause one conjugate 
lir|uid to grow at the expense of the other, but the composition of each will remain 
the same until one conjugate has ceased to exist.. Then, and then only, will the 
temperature begin to fall. Hence for alloys containing a good deal less than 
65 atoms of lead, a large amount of solid matter will form at the freezing point, 
at a very constant temperature. But, as we found to be the case, the period of 
constant temperature observed at the freezing point of each alloy becomes shorter as 
the amount of lead approaches to 65 atoms. 
The gradual change of curvature at both ends of the horizontal line may be due to 
imperfect equilibrium caused by inefficient stirring, too rapid cooling, and other 
causes. Or it may conceivably be due to the gradual aggregation of the lead atoms 
into larger masses preparatory to the separation of the alloy into conjugate liquids. 
The latter part of the curve from 65 to almost 100 atoms of lead may be called 
the curve of solubility of copper in lead, and it ought therefore to give us by 
Le Ch atelier’s equation (2) the latent heat of solution of copper in lead. Unfortu¬ 
nately this part of our curve is very steep, and therefore very difficult to determine 
by our method. 
As we have already mentioned, very small amounts of copper produce the Eaoult 
effect in lead, lowering the freezing point of this metal by the normal amount 
corresponding to a monatomic molecule of copper [loc. cit.). On the flat at the 
lower part of the figure a eutectic point at 60 atoms will be seen. 
The fict that alloys of lead and copper liquate has long been known, and the 
general character of the freezing-point curve of such a system could have been 
predicted from the work of Alexejeff and Konovaloff, but, so far as we are 
aware, this is the first case that has been traced experimentally. 
The bismuth-copper curve has not been carried beyond 9 atoms of bismuth, but, 
from an inspection of the solid alloy, we think that it will turn out to be like the 
lead-copper curve. 
The Copper-Tin Curve. (Fig. 10.) 
The lower line gives the whole curve; the upper line gives, on a large scale, the 
more remarkable portion, from 14 to 27 atomic per cents, of tin. 
The problem of the copper-tin alloys, one of the most interesting in metallurgy, 
still I’emains obscure, in spite of the amount of work that has been done on these 
alloys by Riche, Behrens, Roberts-Ahsten, and many other writers. We fear 
that the results here given, though they complicate this problem, do not solve it.t 
* Pointed out by Ostwald. 
t After a good deal of our work bad been carried out, we found in an article on alloys by M. H. 
Le Ciiateliek, which he was kind enough to send to us (loc. cit., p. 27), a complete Heezing-point curve 
for copper-tin. This curve agrees with ours in having an angle at SnOu^, but it is on too small a scale 
for a comparison of other details. 
