( 170 ) 



represenlatioii I liopc to coniiHunieale after some time and now I wnni 

 to point out onlv the fact, tiiat the point p, which iy liound to a 

 certain concentration can be readied at only one very definite vohime, 

 which holds true for q also. 



By means of the v, .c, ^diagram it can also be made clear, that no line 

 can be drawn of a deiinite limitation between the region for solid B -f- 

 vapoiir and the region of unsaturated vapours. In the region for 

 solid 7i -f" '^'''^Pöiir we have namely a system consisting of two com- 

 ponents in two phases, therefore a bivariant system wherein there 

 are numberless ways in which willi rise of temperature tiio pressure 

 can l)e changed. Consequently it depends altogether on the volume 

 what course w^e follo^v at increase of temperature. 



In order to test the discussed phenomena by an example I chose 

 for the substances A and B ctJicr and (intlmichiiwii. The critical 

 temperature of ether is 190'', hence it is rather low, noi- is the 

 critical }>ressure high, namely d= 36 atmospheres. It is obvious that 

 these two circumstances make tiie experiment much easier. Anthra- 

 cliinon was chosen because this substance is very little soluble in 

 ether, its melting point lies 283'' al)0ve the critical temperature of 

 ether and it is still very stable at its melting [toint. 



The experiments were carried out in thick-walled tubes of 5 cm. 

 length tilled with weighed quantifies of ether and anthrachinon. The 

 ether was free from alcohol and wafei-; the anthi'achinon was crystallized 

 from icevinegar. The ful>es filled with ether and anthrachinon Avcrc 

 closed by melting while in a bath of — 80" (solid Ci).^ -(- alcohol) 

 and then hanged up in an air-bath with little mica windows. This 

 air-bath had been supi)lied with an appai-alus, driven by a motor, 

 for keeping the tubes constanfi\' swinging. The temperature of the 

 baili could be kept constant within 1°. 



In order to determine the solubility curve the temperature was 

 observed at which all the anthi-achinon had been dissolved. In order 

 to determine the critical curve at very slow decrease or increase of 

 temperature this was noted do^vll when formation of nebula occurred, 

 resp. the liquid j)liase disappeared. The average of the two temj)e- 

 ratures was noted down in the graphical representation. If possil)le 

 the volume of the liquid was chosen in such a way, that on reaching 

 the critical temperature the tube was nearly filled with liquid. Only 

 saturation- and critical temperatures for mixtures of deiinite concen- 

 tration being determined by these experiments, only a /, ./'-diagram 

 can of course be constructed from them, which is given in fig. 5. 



From a comparison with fig. 4 it is easy to see that the direction 

 of the two pieces of the critical line and that of the line for the 



