and its bearing on the Nature of Solutions. 



493 



Solvent. 



Dissolved substance. 



Depres- 

 sion*. 



Variation*. 





1 





Per cent. 



Tetrahydrate of 



sulphuric j Water. 



0-08 ] 





acid. 



1 





100 



Do. 



Sulphuric acid. 



004 J 





Monobydrate of 



sulphuric Water. 



0-02 1 





acid. 







100 



Do. 



Sulphuric acid. 



0-01 J 





Sulphuric acid. 



Water. 



0-07 1 

 0-42 ) 



500 



Do. 





Sulphuric anhydride. 





Hexahydrate of 



calcium 



Water. 



0-003 1 





chloride. 









233 



Do. 





Anhyd. calc. chlor. 



0-010 1 





Tetrahydrate of 



calcium 



Water. 



0-007 ) 





nitrate. 









100 



Do. 





Anhyd. calc. nitrate. 1 



0-015 J 





As an instance of a similar character we may quote 

 Hey cock and Neville's determinations of the depression of 

 the freezing-point of sodium by various metals f . 



Molec. depression. 



o 



. . 4-5 



Metal added. 



Gold . . . 



Thallium 4-3 



Mercury 4*5 



Cadmium 3'0 



Potassium 3*6 



Lithium 1*3 



Lead ...... 4*6 



Indium 3' 5 



The variation here is 260 per cent. 



If such variations are not too great to be attributed to an 

 excess of two or three atmospheres'' pressure (and I certainly 

 think they are), they are undoubtedly too great to permit of 

 a theory being founded on the assumption that they are 

 constant. 



It may be noted also that Heycock and Neville's deter- 

 minations with indium, gold, and thallium extended to 

 solutions as dilute as the gases from these metals would be 

 (if their molecules are diatomic), and that even with these 

 " ideal " solutions the variation amounted to 60 per cent. ; 

 had lithium and cadmium been similarly investigated we 

 should, no doubt, have found as great a variation as that quoted 

 above with the stronger solutions. 



* Most of these values are but approximations. 



t Chem. Soc. Trans. 1889, p. 607. The values refer to solutions con- 

 taining as near as possible one atom of the foreign metal to 100 Na. 



