{ 744) 



«„ = l/«,,a,, . '->, = U/'u + ^.) .... (3) 



represents pretty -well the special pi'operties of mixtures. In cases 

 where Ave have no oljservations of mixtures of two substances, 

 the fornnihxe given above will probably enable us to predict the 

 properties of the mixtures of those two substances by means of the 

 a's and b's — i.e. the critical elements — of the components; this 

 circumstance might be of some use in the choice of substances 

 whenever one wishes to observe detinite iihenomena in mixtures. 

 From formulae (1) and (3) we derive the formulae: 



T,k Toic Til 



= (1 — .r) -| ; 



V'p.ik V'pok V'plk 



T,:h Tok Txk 



= (1— .P) H . 



Pxh POk 'P\k 



(4) 



which express how the critical elements Tj-k and />jjt of the mixture 

 taken as homogeneous depend on the composition ; from these formulae 

 also follows, as we know, a linear variation of the critical volume 

 Vxk- That the second of the formulae (4) agrees well with the obser- 

 vations has been shown by van dek Waals '). As to the course of 

 Vxk, tlie curve denoting the variation of tiiat quantity with x not 

 only deviates considerably froui a straight line ") (Verschafkelt 

 and Keesom derive even ïvrnn liieir experimeuts a inaxiuium for 

 Vj-k) but also the quadratic formula caimot be lirought to harmonize 

 with the observations "). 



Not too much importance should be attached to this deviation of a 

 quantity so closely connected with J)*); of higher import it seemed 

 to me to investigate in how far the formulae (4) accurately represent 

 the critical temperatures and pressures, as in connection with the 

 law of corresponding states, of which the approximate validity may 

 be considered to be established, these quantities entirely determine 

 the conduct of a mixture. But also here, of course, we should not 

 strain our expectations too high. 



2. First I have computed from formulae (4) the values of the 

 quantities : 



I) Proceedings Nov. 1897. 



-} Comp. Kamerlingh Onnes and Reinc;.\num. Comm. no. 59/^, Proc. Sept. 2y, 190U; 

 Brinkman, Tliesis for the doctorate, Amsterdam 1904, p. 73. 

 ■*) Ibidem; comp. also Verschaffelt, Comm, Suppl. N". 5. 

 *) For the possible causes of' that deviation comp. Brinkman, loc, cit., p. 75. 



