Mutual Soluh'diti/, of Liguids, 647 



liigbor than the vapour-pressuros of the neiohbonring mixtures, 

 that above tbe critical point for the two liquids there should 

 be a maximum vapour-pressure ; this conclusion has not yet 

 been put to the test. 



c. Butane, 



Tartly with a view to the investigation of mixtures and 

 ])artly for the sake of studying the properties of this substance 

 itself, a quantity of butane was prepared by electrolysis of 

 sodium propionate. Before we were quite satisfied with the 

 purity of the substance and when we had only made a few 

 preliminary experiments, the whole stock was by an accident 

 lost during the night. We hope to resume the investigation 

 of this substance at an early date. 



d, Pentane and Methyl-alcohol. 



The pentane used was obtained from Kahlbaum and it was 

 considered unnecessary for the purposes of this investigation 

 to attempt further purification. 



Two layers were formed with an upper critical point at 

 19°*4 C. This temperature was found to rise under the in- 

 fluence of additional pressure (Table lY.), in other words the 



Table lY. — Pentane and Methyl-alcohol. 

 Critical points of liquids. 



Temp. 



Press. 



Temp. 



Press. 



19-4 







20-25 



40 



19-75 



155 



21-8 



91 



; 20 



(27) 



220 



100 



two-liquid curve separates from the main curve as was ex- 

 plained above (fig. 5). The question remains, whether the 

 liquid-curve is closed on the side of the small volumes or not. 

 If so, the then completely closed curve must contract on 

 heating and at last disappear ; in that case we have to expect 

 a maximum in the critical temperature and therefore a critical 

 curve in the p-t diagram, which is convex towards the ^-axis. 

 The figures obtained do not support this hypothesis, but the 

 observations are not sufficiently accurate to judge of the exact 

 relationship. Measurements of vapour-pressures or composi- 

 tions have not been made yet. 



