( 58 ) 



the influence of the association of the solvent is only appreciable in 

 the term with c*. If water were a normal liquid, we should have 

 had Vm <^ instead of V'es <^ = 0,015 c. (4 c' would then be = VaX Vss.o ^)- 

 Let US now consider what the last expression would have become 

 for JtjgO, when not v^ had occurred in the denominator, but the 

 molecular volume of the solution v. 



When c Gr, mol. are dissolved in 1000 Gr. H,0, then the 

 total volume will be (at 18°) 1001,4 -|- 190 c ccM. [For 1 Gr. 

 mol. = 342,2 Gr. of melted sugar occupies a volume of 190 ccM. 

 at 18° (density = 1,8)]. 



Altogether there are now 34 -f- c Gr. mol., hence the molecular 

 volume of the solution will be: 



_ 1001,4 + 190 c _ 1001,4 1 4- 0,19 c 

 ^' "~ 34 4- c ~ "~3 4~ 1 + 0,03 c * 

 For i\ we found however above : 



_ 1001,4 

 ""' ~ 34 ' 

 so that the value of n^g" with v in the denominator instead of v, 

 w^ould have become : 



1 + 0,03 c . 

 jr,,o = 23,87 c (1-0,015 c) X , T '^^ ^^°^" 



i. e. 



1 + 0,015 c . 



jro = 23,87 c ^ '^ Atm. 

 '' 1 + 0,19 c 



For (weight)normal solutions (c = 1) we should therefore have 

 found instead of ji,,° = 23,87 (1 — 0,015) _ 23,51 Atm., :r,,° 



1,015 

 = 23,87 X -^-j^ = 20,36 Atm. 



Now Morse and Frazer found 24,52 Atm., which is considerably 

 nearer the theoretical value 23,51 Atm. (with v^ in the denominator) 

 than near the inaccurate expression with v in the denominator ^). 



So it is out of the question that the molecules of the dissolved 

 substance should exert a certain pressure comparable with the gas- 

 pressure, for then the volume of the solution as such, viz. v, would 

 have to be taken into account, and not the in that solution perfectly 

 fictitious molecular volume of the solvent v^. 



5. But there is more. We shall viz. derive the expression for 

 the pressure which u)ould be exerted by the dissolved molecules, 



1) With 0,5-normal the two values would have been 11,85 and 10,98 Aim., 

 whereas 12,08 Aim. has been found experimentally. 



