401) 



critical endpoint the vapour branch of a ninth mixture is found in 

 the P-T-tigm-e, the water-content of vvhicli was somewhat e,reater 

 than corresponds to the critical endpoint, and the critical point 

 of which accordingly coincides with F, and no longer lies on the 

 stable vapour branch. 



The distance between this concentration and that of the critical 

 endpoint, however, is so small that the vapour branch still terminates 

 on the three-phase line in the immediate neighbourhood of the critical 

 endpoint. With still greater watei'-content the point of intersection 

 of vapour branch and three-phase line moves to lower tem])erature, 

 and then the vertical tangent will disappear from the stable part 

 of the vapour branch, and this will put an end to the retrogade 

 phenomenon ; I have, however, not continued the investigation of 

 this, as it was perfectly needless for the insight into the phenomena. 



I have realized the intersection between the liquid branch and 

 the three-phase line for the mixtures from 3 to 8 inclusive ; below 

 these points of intersection these mixtures yield the three-phase 

 pressures which are equal for all concentrations, and hence the 

 criterion of purity which I mentioned in the beginning of this 

 paragraph. I have not prolonged the liquid branches of the mixtures 

 1 and 2 so far that the above-mentioned intersection takes place, 

 as this intersection takes place outside the temperature range inves- 

 tigated by me. 



The investigations which have served for the construction of 

 figure 1, are collected in table 1. The vapour tension line of the 

 hexane, the three-phase line determined by means of a mixture with 

 about 47 mol. percent, of water, besides the observations obtained 

 with the nine above-mentioned mixtures, are found there. In the 

 table the critical data are given in bold type ; above them the 

 values of the liquid branch, below them those of the vapour branch 

 are given. 



4. I have constructed the T-.v projection of tiie critical line in 

 fig. 2 by the aid of these data; this projection appears to deviate 

 only very little from a straight line. In the same figure are also 

 given the points of intersection of the liquid branches of the sections 

 for constant concentration of the above-mentioned mixtures with the 

 three-phase line. These points of intersection indicate the states where 

 liquid rich in liexane exists by the side of a very small quantity of 

 vapour and of liquid rich in water, and so the locus of these 

 points of intersection yields a liquid branch of the three-phase region. 

 In the critical endpoint this branch passes with a horizontal tangent 



