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CHEMISTRY: WASHBURN AND READ 
CeHe: 5.48^ Diphenyl, CeHsCeHs: 68.95°. Naphthalene, doHg: 80.09°. 
The directly measured values and the computed values of the three 
eutectic temperatures were found to be as follows: 
Benzene-naphthalene; measured: —3.48°; computed: —3.56°. 
Benzene-diphenyl ; measured : —5.8°; computed : —6.1°. 
Naphthalene-diphenyl; measured: 39.4°; computed: 39.4°. 
The close agreement between the calculated and observed values of 
the eutectic temperatures shows that these three solutions are very 
close to ideal solutions in their behavior; for this method of testing 
them is a very rigorous one. 
The above given differential equations represent the most generally 
applicable freezing-point and solubility law which we have at present. 
By means of this law we can calculate the freezing-point of a given solu- 
tion or the solubihty of a given solid in a liquid for all solutions which 
fulfil the necessary conditions. These conditions are (1) the heat of 
dilution of the solution for the range of concentration involved must 
be practically zero; and (2) the dilution of the solution must not be 
accompanied by the occurrence of a chemical reaction of any kind. 
The quantity L in the equations represents in general the molal heat of 
solution of the crystalline substance in its own saturated solution. For 
ideal solutions this heat of solution is of course identical with the heat 
of fusion. The above law should be generally employed in place of the 
more common 'dilute solution' laws, which are only special cases of it. 
In closing this paper it may be worth while to point out two examples 
of the use of the equation given above which do not seem to be famihar 
to most chemists, and especially to those chemists in whose special 
fields of work they are of chief interest. 
1. The results of the search for some general principle concerning the 
solubihty of substances in each other is usually summed up by restating 
the old principle that similia similihus solvuntur. In the light of our 
present knowledge we can, however, go somewhat further than this 
simple quahtative statement, and can formulate the following quanti- 
tative principle: 
When a crystalHne substance A is dissolved in any solvent B with 
which it forms an ideal solution, its solubility (expressed in terms of 
its mole-fraction in the saturated solution) is entirely independent of the 
nature of the solvent B, and is therefore the same in all such solvents. 
The solubility depends merely upon the temperature and upon the melt- 
ing-point and heat of fusion of the crystals A, from which data it can 
in fact be readily calculated. This important principle, which follows 
directly from the above equations does not seem to have been gener- 
