( 162 ) 



If tlic giupliical I'cpresenlatioii ul" Tk as fmictioii of ,/', is a curve 

 (Cont. II, p. 45), lying everywhere above tlie tangent, wliic-li is the 



case when 7-74-7-7 — 7-7- i^^ positive, then 7^, + (''2 — -^'i) -7-" ^^ 



smaller than 1\ . 



If we draw a tangent to liie curve in the point .I'l, this tangent 

 cuts the ordinate of ./'^ in a jtoint which lies lower than the curve, 

 and the distance from that jioint of intersection to the curve is a 

 measure for the quantity of heat required for mixing the condensed 

 vapour with the li((ui(l pliase considered. As ft''^. consists of two 

 terms, the latter of which is only negative, when the mixing in the 

 liquid state is atteiuled by absorjttion of heat, we are not justified 

 in expecting that this latent heat of mixing alone determines the 

 sign of fi".,. 



Physics. — "On Rc-cuitcs of mivture.'i of acetone and ethyl-ether 

 and of carbon tetrachloride and acetone at 0° 6'." By G. 0. 

 Grrkits. (Communicated by Prof. J. D. van dkk Waai.s). 



(Communicated in the meeting of June 20, 1904). 



The imperfect concordance found by Cunaeus ^) between the rela- 

 tion deduced by van uek Waals *) in his theory I)et^veen the vapour 

 tension o\er a mixture of two liipiids, the molecular concentration 

 of the vapour and that of the li(piid, induced us to take up the 

 investigation once more according to the same method as had been 

 used by Cunakus and with the same substances, acetone and ethyl-ether. 

 Afterwards also mixtures of carbon tetra(!hloride and acetone were 

 examined. 



It had viz. appeared, that improvements might be applied to the 

 method of investigation. 



By means of the determination of the refractivity of the vapour, 

 both of the simple substances and of the mixtures, the molecular 

 concentration of the \apour was determined by means of the law 

 of BioT and A rag o . 



This determination of the refractivity w^as made according to the 

 method of Lord Rayj,eigh '') also follow ed by Cunaeus "). 



^) Cunaeus, Proefschrift, Amsterdam, lO(K), biz. 47 — 51. 



-) VAN DER Waals, Arch. Néerl. 24, hlz. 44 : Gontinuilat des gasf. und fliiss. 

 Zuslandes II, biz. 137. 



=*) Rayleigh, Proc. Roy. Institution, Vol. XV, Part. 1, pag. 1 ; Proc. Roy. Soc. 

 Vol. 59, bk. 201. 



*) Cunaeus, Proefschrift, biz. 4—0. Proc. 



