314 REPORT—1890. 
are entirely in ignorance at present as to the possible complexity of liquid 
molecules. It is interesting to note that a similar complexity of mole- 
cular grouping must be admitted if we accept Raoult’s original statement 
that one molecule of any substance dissolved in 100 molecules of a solvent 
lowers the freezing point of this latter by about 0°°63; for, if this be so, 
we must assign to the molecules of the various substances entered 
in the second column of Table I. the magnitude there indicated when 
they are dissolved in the solvent named in the first column, for it requires 
that proportion of these bodies to lower the freezing point of 100 mole- 
cules of the solvent by 0°:63; and, amongst these few instances which I 
have collected from my own determinations, we find molecular aggregates 
containing as many as 200 of the fundamental molecules, and even this 
number, I may mention, probably understates the complexity to a very 
considerable extent ; for the depression in this and some of the other cases 
had to be estimated from that observed with solutions containing as 
much as 10 gram molecular proportions to 100 of the solvent, and 
the molecular depression increased rapidly with the strength of the 
solution: 1000H,O would probably be a low estimate of the complexity 
of the molecules of water when dissolved in a large excess of the hex- 
hydrate of calcium chloride, a complexity comparable with that of the 
hydrates, which my other work has indicated, and that too in the case 
of that very substance which these hydrates contain—water. 
Taste I.—Molecular Weights of Substances in various Solvents. 
Dissolved substance producin 
Solvent 0°65 depres . 
100(H,80,.H,0) 32H,0 
3 63H,SO, 
100(H,S0,.4H,0) 8H,O 
sy 15H.SO, 
100([CaN 0, ],.4H,0) 90H,O 
* 42Ca(NO,), 
100(CaCl,.6H,O) 210H,O 
” 63CaCl, 
Now as to the question of how far the theory of osmotic pressure, and 
the results on which it is based, are antagonistic to the hydrate theory : 
and let me first define clearly the position which I take in this matter. 
I do not for one moment call in question any of Raoult’s classical work, 
which is now so familiar to us, nor do I question that these results reveal 
the existence of a depression of the freezing point which is approximately 
and generally constant; and I consequently admit that we can generally 
obtain an approximately correct value for the molecular weight of the 
substance by observing the depression which it causes ; nor, again, do I 
wish to question the correctness of the mathematical relationship which 
van ’t Hoff and Arrhenius have shown to exist between osmotic pressure, 
the lowering of the freezing point, and other properties, provided we 
accept the fundamental assumptions on which these calculations are 
based—the truly gaseous nature of dissolved matter, and the dissociation 
of salts into their ions. But what I do question is that the facts of the — 
1 Other instances of high molecular weights are mentioned by Brown and Morris ¥ 
(Chem. Soc. Trans. 1888), and Gladstone and Hibbert (Pil. Mag. 1889, vol. ii. p. 38). 
* Determined from the freezing points of very weak solutions. 
