755 



of b for H, ^). But then only Amagat's experiments were known, 

 and I calcnlated the /;-valnes at 0°, 100°, and 200° C. on the 

 supposition that a was constant = 300 . 1Q~^. The thus calculated 

 values were compared witli those which would follow from the 

 "equation of state of the molecule", published at the time bj v. d. W.; 

 and for greater pi-essnres, from 500 atm. to 1000 or 2800 atm. a: 

 good agreement was found. 



But later on I saw that not only this formula of van der Waals, 

 but every interpolation formula — both with ascending powers of 

 p and with those of v~'^ — gave equally good agi-eement. The 

 objections to van der Waat.s's formula (besides theoretical difficulties; 

 about which in the conclusion) lie chiefly in the too small values 

 of è„, yielded by it. Thus for 0° was found è^^ 463.10-6, ^yhich 

 is still possible with respect to 6,/ =917. 10 6. But for 100° C. 

 b^ was calculated = 386 {b,, likewise ==: 917), and for 200° C. even 

 è„ = 306 (^>„ = 910). 



Besides I came afterwards to the conclusion that the supposition 

 a independent of T could no longer be maintained, as for T]; the 

 value of ük had lo be considerably higher than 300.10"^. But only 

 from the recent determinations of Kamerlingh Onnes c. s. it appeared 

 very clearly that the value of a also below Tk became greater and 

 greater, and even gets into the iieighboui-hood of 700. 10 ^ for 

 — 257°, rtvfc being only = 486. lO-e. 



The very recently published direct determinatiDn of the critical 

 point by K. Onnes, Dorsman and Holst enabled me to revise my 

 calculations and to supplement them. As the above mentioned iso- 

 therm determinations of K. 0. c. s. all refer to relatively great 

 volumes, only about the limiting values bf, there is something to be 

 derived with certainty. But these values, and also those of the 

 corresponding values of a (how the separation is possible, ' will 

 appear presently) appeared to be dependent on T to such a high 

 degree that the dependence on v suggested by v. d. W, becomes 

 quite unnecessary — at least below 7\ and for the great volumes. 

 Thus e.g. at H^ the ratio of the value of a at 16° abs. to that of a 

 at T]c is already about 1,4, whereas the ratio of the corresponding 

 values of a for Fluorbenzene amounted to about 1,5 (see the table 

 in § 1). . 



Whether possibly for .small volumes the value of a will yet prove 

 to be dependent on v, is another question. But in virtue of the 

 above, I yet consider this not very probable. ") 



1) These Proc. of March 1903. 



2) And if this should prove to be the case, a prop'orlionalily with e.g. v—^/s 



