i051 



Uemarh. 



Before proceeding (o llic disciissioii of tlio dependence on tlie tem- 

 pemtiire of y' and y, a i-einark may be made in this context, con- 

 cerning the necessary conseqnences of the above considerations with 

 regard to the conrse of the "strriKjht dlameki''\ When namely for a 

 substance we descend from the ciütical temperature to lower tem- 

 peratures, h,j — b^, so also y, will continually descend ; so that the 

 slope of the straight diameter for an arbitrary temperature (which 

 slope at eveiy temperature will depend on the type of the isotherm 

 at the considered temperature, determined there by b,, — />J, will also 

 have to decrease from the value y^- measured at Ti- down to the 

 lowest value, i. e, y = 7.2- holding for an ideal substance {Tk=:i)). 

 In other words the straight diameter cannot possibly remain strau/ht, 

 but will exhibit such a curvature, that the final direction at J'=0 

 (supposing that liquid volumes could still be realized at these low 

 temperatures) approach to about 0,5. 



It is self-evident that the Imv according to which this decrease 

 takes place 7ieed not be the same as the law that determines the 

 decrease of y' or y with the temperature, since for one and the 

 same substance yk at the critical temperature is, indeed, in direct 

 relation with the course of the straight diameter there, but this is no 

 longer the case, of course, below the critical temperature, where 

 bk : b^ and y have lost theii' original meaning. A .s^é/Mra/é? investigation 

 will have to decide later on, what the relation is of the real direction 

 of the straight diameter below 7\-, and the temperature. 



That the change of direction for ordinanj substances will ne\'er 

 be very great, however, at least not in the beginning, follows from 

 this that according to the law of variability of y to be drawn up 

 presently — with which the variation of direction of the straight 

 diameter in any case will run parallel — a decrease of y of any 

 importance will not take place until ixi lower temperature, i.e. at 

 temperatures which ai-e considerably lower than the critical. For 

 substances as Hydrogen and Helium, where the critical temperature 

 lies so near the absolute zero, a more pronounced curvature of the 

 straight diameter will of course be expected. 



15. A relation betjoeen yk and Tk. 



It was then found by me that the quantity yyt at 7\., i. e. the 

 (reduced) coefficient of direction of the straight diameter, is in a 

 very simj)le relation to Tk. namely according to the relation 



^t^^::=-2y/.-l=0,0:i8l/r^ ..... (85) 



