( ITG ) 



So this is the soiight-for expression tor tiie clumge in ^i^, caused 

 bv the addition of ./■ gr.niol. salt. 



l—.v 

 3. Now on 1 saltniol. there are gr.mol. K,0 (normally 



.V 



fl—.'v\ 1—.V 

 reckoned), among which tliere are evidently ^/.A 1 ^i? = ii 



single mol. In consequence of the fact, that the slate of dissociatiou 

 of the watermolecules is changed by the solved substance, this nundjer 

 according to (3) will amount to 



1 — .r 1 — .i; 1 — ,v X 



/? = 1^0 + X /?« (!-.?«) '■ -, , 



.?• X .V 1 — .V 



that is to say an increase of 



1 — .?• .V 



,?• 1 — .V 



And now it is clear that, as was already observed above, the 



1-.V 



one factor of this product, viz. , approaches to go, while the other 



,v 



factor, viz. /?„ (^ - i^o) ' ^; > ajiproaches to 0. The pi-oduct howexer is 



1 — .1' 



evidently finite, viz.: 



^ = i..(i-,j.,); (4) 



Now if (^ is the heat, absoi-bed when 1 gr.mol. (18 Gr.) H^O 

 changes from the state of double molecules to that of single molecules, 

 then the heat, absorbed in consequence of the state of association 

 being changed by J mol. of the solved substance, is: 



W=i3Al-,S,)iQ. (5) 



And this heat it is, which we have to take into account for 

 associa ting sol \'en t s . 



For H*0 at 18° (? = 0,21 '), ^^o that the factor ,?„ (1 — i?„) becomes 

 = 0,17. Further Q (as 1 calculated some time ago ')) = ± 1920 

 gramcalories, so for water (at 18^) xvill i)e: 



W — 320 ; (5a) 



If the solved substance is no e/ectroli/te, then i = l, so for much 

 diluted solutions about 325 gr.cal are absorbed with ereri/ concen- 

 tration, if 1 gr.mol. is solved in the water, oidy in consequence of 

 the change in the degree of association of the water; for salts, acids 



1) Zeitsdir. fiir Pliys. Cli., 31, p. i (1899); Lclirbncli der math. Cliomie, p. 30 

 (1901K 



2) Z. f. Ph. Ch., 31, p. 5 (1899); Lehi-b. der math. Chem., p. 37 (1901). 



