COMPLETE FREEZINO-POINT CURVES OP BINARY ALLOYS. 
31 
Column (3), the Atomic Percentage of the second metal, gives the number of atoms 
of the second metal in every 100 atoms of the alloy. It would be more satisfactory 
if we could calculate the number of molecules of the second metal in every 100 
molecules of the alloy, but unfortunately we can only make uncertain guesses as to 
the molecular weights. As before, by subtracting the number in column (3) from 
100 we get the atomic percentage of the 6r.st metal. Columns (2) and (3) are not 
calculated beyond the second decimal place, as this gives a degree of accuracy equal 
to that of the freezing points in column (4). 
Column (4) gives the freezing point. This temperature was read to one-hundredth 
of a degree, but in the tables we, as a rule, only give the tenths of a degree. 
Column (5), the Atomic Fall, is obtained by dividing the total depression of the 
freezing point, taken from column (4), by the atomic percentage taken from column 
(3). This column shows how far the law of proportionality between the concentration 
and the total depression of the freezing point holds good. For concentrated solutions 
the atomic fall has no simple meaning, and in such cases it is not given in the tables. 
In applying equation (1) to the case of dilute solutions, for which alone the conception 
of the atomic fall is useful, we must regard clx as identical with 1 — x. This is the 
atomic percentage divided by 100, so that the atomic fall is yoq • dd/c/x, a quantity 
which equation (l) tells us is equal to •O20“/a;X. If we use tlie more accurate 
equation (2), then the atomic fall is 
O-do 
•02 log^. 
The two expressions become 
identical when x is unity. 
Numbers in column (4), which are enclosed in brackets, are second freezing points, 
corresponding to a eutectic state. 
Each series in a table corresijonds to an entirely new alloy, and the horizontal 
spaces dividing a series into sections indicate that a portion of the alloy has been 
extracted from the crucible and the experiments continued with the residue.* It 
will be seen that the freezing point was always taken after as well as before such an 
extraction. 
The notes and remarks at the end of each table are substantially copied from the 
laboratory note-book. 
* Tal)le IIa contains examples of this. 
