496 Mr. Pickering on the Theory of Osmotic Pressure 



and that, too, through the agency of the water, which is as- 

 sumed to have no action at all. 



Influence of the Nature of the Solvent. 



It is found that the nature of the solvent, instead of being 

 without influence on the results, as it should be according to 

 the osmotic-pressure theory, is one of the main factors in 

 determining them. 



Thus, for instance, sulphuric and hydrochloric acids give 

 the normal high values when dissolved in water, but solutions 

 of the same strength in acetic acid show the abnormal half- 

 values : formic and benzoic acids, methyl, ethyl, butyl, and 

 amyl alcohols, as well as phenol, all give normal depressions 

 with acetic acid, but abnormal ones with benzene. Many 

 other instances of a similar character may be selected from 

 Eaoult's data, but none of them show the influence of the 

 nature of the solvent in such a forcible manner as the fol- 

 lowing : — 



Molec. Depress. 



1-072 



0-02 



0-08 



0-003 



0-007 



0-55 



H 2 dissolved in 100 H 2 S0 4 . . . . 



100 (H 2 S0 4 H 2 0) . . 



100 (H 2 S0 4 4H 2 0). . 

 „ „ 100 (CaCl 2 6H 2 0) . . 



100(Ca(NO 3 ) 2 4H 2 O). 

 „ „ 100(CH 3 COOH) . . 



The variation of this constant (?) calculated on the smallest 

 value amounts to 35,600 per cent. Again, 



H 2 S0 4 dissolved in 100 H 2 2-15 



100 (H 2 S0 4 H 2 0) . . . 0-01 



J) J5 



100(H 2 SO 4 4H 2 O) . . 0-04 



100 (CH3COOH) . . 0-31 



Extreme variation 21,400 per cent. Similarly, 



CaCl 3 dissolved in 100 H 2 2'773 



100 (CaCl 2 6H 2 0) . . . 0-010 



Variation 27,600 per cent.; and 



Ca(N0 3 ) 2 dissolved in 100 H 2 .... 2-50 



100Ca(NO 3 ) 2 4H 2 O. 0-015 

 Variation 16,600 per cent. 



