401 



fïence j/a will have the same value for 7a double molecule as for 

 1 single molecule. / 



The same thing is assumed with regard to the heat capacities 

 ^, and k^. There too — especially for larger molecules — no con- 

 traction of the value is supposed. 



Thus instead of (1) the following form is found: 



toz=q + n,n^ ^— ^ ^ p _^ __ At; . (1„,,.) 



The values of iv^ and iv^ are found in an entirely analogous way 

 as in ^ 2, viz. from (cf. equation (!")): 



in which further: 

 a, a, «, / a^ «' ^ , 



t'l^i" ("/)a<> (^ik Vl^/U" (f'lk» J VC^Ja" (^i)/3i 



(^i-^, V + 7-T^v~ (^i-i^/) ^^ ' 





as 



2 



so that (fj^, — (vj^^ozi^ (1^1 — ,i/)Ai. In this A^ represents the change 

 of volume (contraction), when in the mixture Vs double molecule 

 becomes 1 single molecule. 



This quantity A, can possess a considerable value. The pheno- 

 menoji of the maximum-density of neater e.g. tinds its explanation 

 in the great value of A^, so that below 4° C. the thermal expansion 

 is even exceeded by the (liminutioii of volume in consequence of 

 the progressing dissociation of the double molecules. Above 4° C. 

 the thermal expansion will predominate '). 



The same thing holds for — — Lv,, so that, taking into account 



that also 



1) This explanation, given by me for the first time in the van 't HoFF-volume 

 of the Zeitschr. f. ph. Ch. (Bd. 31, 1899, p. 1 et seq.) ) more than 20 years ago 

 (see particularly p. 12—16), is not yet found mentioned in any handbook. Except 

 for a few favourable exceptions this is also the case with many other theories, 

 rules and explanations given by me. 



26* 



