October 23, 1890] 



NA TURE 



629 



wholly untenable ; and it must be specially noticed that one of 

 the substances showing these irregularities — alcohol — is a non- 

 electrolyte, in which case the theory of dissociation into ions 

 cannot be brought forward as an explanation of their existence. 



It is important to observe that when we pass on to stronger 

 solutions, where the actual magnitude of the deviations becomes 

 so great that they would be revealed by the roughest experi- 

 ments—deviations of even 70°— and where, I believe, even the 



supporters of the osmotic pressure theory would not hesitate ta 

 attribute them to the disturbing influence of hydrates; these devia- 

 tions occur in precisely the same irregular manner as they do in 

 the case of weak solutions, and must evidently be attributed to the 

 same cause. The results with alcohol given in Fig. 2 illustrate 

 these irregularities in a very striking manner. It must also be 

 pointed out that, apart from the irregularity of these deviations, 

 their very direction shows that they cannot be attributed to the 



■02 •04. •OS. -OS -to -It '14- 



Molecules dissolved in 100H2O. 

 ;. I. — Deviation from regularity of the freezing-points of very weak solutions. 



dissolved particles being brought within the sphere of each 

 other's attraction, as in the case of the deviation of gases from 

 Boyle's law, for the result of this would be that their attraction 

 on the particles of the solvent would be diminished, and the 

 freezing-point of this latter would consequently be lowered to an 

 abnormally small extent, whereas precisely the reverse is the 

 case in nearly every instance at present investigated : the 

 freezing-points of strong solutions are abnormally /ozu. Various 



instances of this will be found in the P/iil. Mag., 1890, vol. i. 

 p. 500, that of sulphuric acid, which is illustrated here in Fig. 2, 

 being by no means the most prominent ; while the case of 

 alcohol, now for the first time displayed (Fig. 2^, is the only 

 exception which has, so far, been :met with, and that is an 

 exception only in the case of excessively strong solutions. 



From the instances above mentioned some answer may be 

 obtained to the third question — whether the molecular depression 



Mols. H0SO4 to 100H2O. 

 -Freezing-points of sulphuric acid and alcohol solutions. 



is independent of the nature of the dissolved substance. The 

 values obtained with these four substances, taking solutions of a 

 strength corresponding to that of their gases, are : — 



Calcium chloride 

 Calcium nitrate 

 Sulphuric acid 

 Alcohol ... 

 a variation of 30 per cent. 



2° -850 

 2° 744 

 2°-3i3 

 2°-i8o 



which must give an emphatic denial 



to the idea of absolute constancy ; and if we take instances from 

 NO. 1095, VOL. 42] 



other substances, where the data available refer to solutions of 

 somewhat greater strength, we find that the very substances on 

 which the idea of constancy was originally founded show 

 variations reaching 60 per cent. {Phil. Mag., 1890, vol. i. p. 

 492), while in other cases, which I have quoted elsewhere {loc. cit., 

 p. 493),^ the variation attains the still larger dimensions of 260 

 per cent. 



' The depression produced by H3O in 100H0SO4 is i°'o7 instead of o°'07 

 as there given. 



