( 8i ) 



The equilibrium between the two phases is obtained by stirring 

 with the aid of' an electro-magnetic stirring-apparatus, as has lately 

 been described by van Eldik ') (see § 6). In this manner a perfect 

 equilibrium must be obtained within the wide reservoir. The cocks 

 Ai and B\ are wide open during the stirring. Care should be taken 

 that the composition of the pubstance in the space B should be the 

 same as that of the rest of the vapour-phase in if', and therefore, 

 after sufficient stirring (or while carefully continuing the stirring) 

 as much of tlie vapour as is contained in the space B must be 

 slowly blown off by slightly opening the cock B^, after which the 

 cocks Z?2 and Bi are successively shut. In tapping from the liquid- 

 phase the same is done with respect to the cocks ^i and A^. 



The spaces ^J and B are 0,0778 and 3,25 c.c.m., while the volume 

 of R is about 150 c.c.m. So we may assume that the change of the 

 composition of the liquid and of the vapour during the tapping may 

 be left out of consideration, if the tapping be done with the neces- 

 sary care in the way described above, and that the compositions of 

 liquid- and vapour-phases, found by analysis, indicate the composi- 

 tions of coexisting phases at the temperature and under the pressure 

 at which the tapping is done. I intend to connect with the present 

 apparatus the compound hydraulic pump for moving coexisting phases 

 (described in the Proceedings of the Meeting of May 27th 1897 p. 

 21) by means of which the permanent equilibrium between the phases 

 may be still better secured. 



In order to keep the temperature constant, the apparatus is placed 

 in a water bath (see § 5). 



The pressure of the coexisting phases is measured before and after 

 the tapping by means of the manometer connected with p (see § 4). 

 The average of both measurements is taken as the pressure to which 

 the coexisting phases belong. 



When one measurement has been performed we may make a second 

 determination by tapping once more, and so on, as long as the 

 quantity of the liquid phase in the reservoir is sufficient. At each 

 successive determination we find a new value for the pressure to 

 which the new pair of coexisting phases belongs. 



In this way a series of a certain number of successive determina- 

 tions was generally made at the same temperature. 



§ 3. Description of the apparatus (fig. 2 — 4). 



The reservoir B consists of a drawn brass tube (long 55 cM. 

 internally) closed at both ends by a plug screwed and soldered in 



V. Eldik, Prooeediiigs of the Meeting of May 2'J '97 p. 2U. 



