418 



liquids the value of — increases imioh at the lower temperatures, 



while to the other side many liquids of group .4, which e. g. between 



25° and 80° (/. show rather normal values ot ^ , will have abnor- 



mally low values for it at the higher temperatures. As fai- as the 

 not numerous determinations of the specific gravities mal-ce a con- 

 clusion possible in this respect, to this group B can be brought also 

 the molten salts of ihoi ii\ki\\'\-\\\e{x\h\ Sodmniclilorlile {0,Q), l\it'jssmm- 

 chloride (0,G4) ; etc. Furthermore the hitherto observed dependence 

 of X and t for.: Sodiumsitlfate, Sodinmmo/i/hdate, Sodiumtungstate, 

 Sodium pkospliate ; Polassiiunhroiidde, Foias-siuni iodide, Potassium- 

 phosphate, -inoli/hdatc, -tungstate ; Lithiumsulphate, Lithiummetaborate, 

 Litldummethasilicate ; etc. etc., — seems to prove, that also with 



these sails the values of .-- will appear to be remarkablv small. 



ot 



§ 2. The j)revailahle opinion is, that the liquids of the group B 

 most ditfer from those of grouj) A in this respect that they would 

 be associated, while the licpiids of group A would be normal ones. 

 Regarding those liquids, which show an almost linear dependence 

 of X and t (type 2j, the "association-coefficient" x is then calculated 



3_ 



( 2,2 1 2 

 from the expression : .i* = — - — f ; while in the cases, where such 



a linear dependence can not be supposed, several other formulae are 

 proposed ^). After what has been said, however, it can hardly be quite 

 sure, that such a calculation of the degree of association can be 

 thought of as a step in the good direction. For among the substances 

 of group A the greater number are of a kind, whose ƒt-^curves 

 belong to types 1 or 3; type 3 can be thought moreover again to 

 be in so far in agreement with the postulations of the theory, that 

 here at least exists the possibility that the curve will approach 

 to the ^axis asymptotically in the vicinity of the critical temperature. 

 If now however the supposition were right, that a decrease of 



1) After VAN DKR Waals (Z. f. phys. 13. 716. (1894)) e. g., a relation of the 



ÖX / T \^ 



form: — == ^ I 1 — — -- 1 _ in which B at the critical temperature should 



have the value: Ve- but in praxi appears to be: about 1,23, — would reproduce 

 in many cases the dependence of ^ and / I o a ratlior snffi icnt degree. 



