COMPLETE FREEZING-POINT CURVES OF BINARY ALLOYS. 
57 
as an average from the lead and bismuth, an atomic fall of 11'6° at a concentration 
of 1*2 atoms. A mean of the two numbers for tin which come within these limits 
gives 11'5° at 1‘5 atoms. These numbers used with equation (2) give a value of X 
very slightly greater than the above. Hence we may say that the results of our 
experiments on the solution of lead, bismuth, and tin in copper lead to the value 
50 calories for the latent heat of fusion of copper. We should expect this to be more 
probably too high than too low. 
The atomic fall due to gold dissolved in copper is 5'7° for a mean concentration of 
2'26 atoms, using the last three values of the gold-copper table. This corresponds 
to a value for infinite dilution of 5*8°, which is very nearly half the above value given 
by lead, bismuth, and tin. Silver in copper produces a fall of about 8‘2°, that is, 
rather more than two-thirds of the normal fall, 11’7. 
The half value given by gold may mean that when in dilute solution in copper the 
gold molecule consists of two atoms, but it will be well to wait for further data 
before speculating as to the cause of these abnormally small depressions of the 
freezing point. 
I’he data for the atomic fall, when silver is the solvent, are more numerous, but 
not on that account easiei’ to interpret. As before, the values given by lead and 
bismuth are the largest; the most probable value being near 10*3°. This value 
leads to a latent heat of 27 calories for silver, a value considerably greater than 
Person’s value of 21. Here, also, as in the case of the copper, we must hope tliat 
further data will help us to decide whether these atomic falls really contain the key 
to the molecular condition of the metals in solution. 
The Silver-Copper Curve. (Fig. 6.) 
This, looked at as a whole, in the light of the theory of Section 1, does not n,t 
first offer a singularity or an indication of the existence of a compound ; but, examined 
more closely, there are two points worth mention. 
The first is that the depressions of the freezing point, even for very dilute solutions, 
are abnormally small, and the atomic falls decrease slowly in value with increasing 
concentration. The small depression makes it probable that the molecule of either 
metal, when in dilute solution in the other, is complex, consisting of more than one 
atom. The decrease in the atomic falls is by no means rapid, as may be seen from the 
slight curvature, but so far as it exists, it is an argument against the existence in the 
liquid alloy of molecules of a compound. 
The other feature lies in the exact coincidence of the eutectic alloy, Levol’s alloy, 
with the formula Ag^jCug. This struck us in our first series of experiments, but, as 
during a long series there is always some loss of metal, we thought it well to carry 
out new experiments, starting with an alloy of a composition nearly corresponding to 
that of the eutectic point. Table Ic. gives this series, and the results are plotted in 
MDCCCXCVII.-A. I 
