( 274 ) 



Also mixture ]II has been investigated by iis in a tube without a 

 widened part, and this accounts, no doubt, for the bad agreement 

 of the vahies found bv us for this mixture and for the preceding 

 ones. For it was, indeed, possible to ascertain that there was some 

 liquid in the tube, which was for the rest entirely fdled with 

 the gas-mixture, but whether it split up into two layers could not 

 be ascertained. We thought, however, that we might state that 

 there was a region for which the volume did greatly decrease 

 and the pressure remained nearly constant, which would, therefore, 

 point to the existence of more than two phases, but these pressures 

 do not harmonize very well with the A's for other mixtures. 



Our mixture IV, ./; = 0,0022, is the only one that we could watch 

 in a widened tube for a short time. This enabled us to use not too 

 slight a quantity of nitrobenzene, a little more than 5 mg., in spite 

 of the small x, and thus to demonstrate the unmixing very clearly, 

 whereas this had been impossible for the former mixture with 

 -iz 3 m.g. 



In view of the weakness of our tubes, we wanted first to examine 

 the three-phase line and then if i>ossible determine the end-conden- 

 sation pressures, so as not to be obliged to expose the tubes at once 

 to those higher pressures. When, however, also this tube burst before 

 w^e had been able to follow the whole three-phase line, and it appeared 

 from the observations that we were still very far from the point 1, 

 which, accordingly, will not be much displaced with the temperature, 

 we resolved to abandoji the research of the double retrograde con- 

 densation also for the system carbonic acid and nitrobenzene, hoping 

 to resume it afterwards with more favourable components. 



It seemed, however, of importance to us to determine the con- 

 centration of the lower critical endpoint ; we expected that this would 

 lie at much larger x. 



Our next fdling, however, now again in a straight tube with 

 ,7? z= 0,476 showed that the region of non-miscibility will lie entirel}' 

 in the left half of the j>figures, and so did some following mixtures, 

 the tubes of which gave way at the first observations. 



So ^ve ha\e not succeeded in fixing the utmost limit of the region 

 of non-miscibility, the place of the point 3 at the temperature of 

 the upper critical end-point. 



We could conclude from the mixture .v = 0,121 that we were 

 still on the righthand side of the lower end-point, and also on the 

 righthand of all the plaitpoints at higher temperatures, because every 

 time after the vapour phase had disappeared at the end of the A-region 

 we saw the phase 2 disappear on compression. Though the required 



