608 



(lie so-called quasi change, which would be caused by the diminution 

 of the old factor 4 (o about 2 in consequence of the partial over- 

 lapping of the "distance spheres". We namely assume that the volume 

 available for the calculation of the pressure is immediately found by 

 subtracting the volume of the molecules ?n from the total volume i', 

 always assuming that the kinetic energy of the moving molecules 

 and molecule groups, with the permanent gradual interchange of 

 the energy during the collisions, is continuously absorbed by the 

 surrounding medium (see 1 p. 809, and IV, p. 464 at the bottom), 

 and is finally after subtraction of the internal molecular pressure 

 observed as "external pressure". 



It will be asked what part the so-called association or quasi-asso- 

 ciation plays in these considerations. 



Before answering this question I will first state clearly my opinion 

 about the difference between association and quasi-association, which 

 I hold in connection with the following considerations. We may 

 brietly express this diiference in the foUowijig way. 



Real association is quite individual and has a permanent character ; 

 it quite depends on the chemical nature of the molecules (whether 

 there are e.g. still free valencies or minor \alencies present etc.). 

 Water, alcohol, acetic acid are associating substances — ether, 

 benzene, chloi'obenzene etc. are ?io??-associated substances. 



Qwrï^i-association on the other hand in consequence of the action 

 of the molecular forces, when two molecides get into each other's 

 neighbourhood, and which gives rise to the formation of temporary 

 "molecule aggregations", is entirely the same for all snhstaiices in 

 corresponding states, and of transient, albeit stationary nature. 



This last form of association, which has been particularly studied 

 by VAN DER Waals, is competent to explain why with the ordinary 

 kinetic view (which, when all the active factors are taken into con- 

 sideration, must also lead to the truth) not /)^ ■= 4m is found but to. 

 The theory which — evading the separate consideration of the moving 



under the notice of many, may appear again from an article by A. Wohl in the 

 Z. f. ph. Gil. 87, p. 1 — 39. This aullior thinks he can set everything right by an 

 equation of state of the wholly unjustifiable form 



RT a ^ c 



V — v{v — b) V 

 in which a, b, and c are constants. That it is also possible to arrive among others 

 at llie accurate values of the critical data by putting b variable with v in the 

 ordinary equation of stale, does not seem to have occurred to him. Also von Jüptner's 

 many articles convey an impression of his not being at all in touch with the new 

 investigations in this department. 



