( 240 ) 



^ 1, the temperatui-e is dillereiit in (lie different portions of the 

 gaseous mixture. Tlie portion (see fig. 3 § J) at tlie temperature of 

 in\estigation 7' is separated from tiiat at ordinary (or liigher) tem- 

 |)eratnre T" by a series of layers (in the capillary) of which the 

 temperatures range from the highest T" to the lowest T. One of 

 these temperatures we shall call T'. 



This circumstance involves 

 several restrictions and conditions 

 in Ihe aj)plicalion of the method. 

 In ordei' to make measurements 

 possible for all compositions .c the 

 temperature T" must be taken or 

 raised so high above T, that on 

 (he y^/'-diagram (fig. 4) (he vapour 

 bi-anch of the binodal curve of 7'" 

 does not intersect the liquid binodal 

 curve T. Then we need not fear that 

 condensation begins at 7'" while 

 condensation takes place during 

 the transfer of the mixture from 

 ^'B- ^- the com])ression tube (or |)erhaps 



(he vohiinenonieter) (o (he piezometer. At T" we (hen always have 

 a gaseous mixture of (he original composition. Wheji the above- 

 mentioned curves intersect, as is represented in fig. 4 for the case of 

 7", we can make measurements only for the compositions represented 

 l)y |K)iji(s outside the region included apju-oximately be(weeiu/and 6^ 

 Even if, without condensation taking place in the compression 

 apparatus (or perhaps volumenometer) the gaseous mixture caji be 

 transferred to the piezometer, the part of the capillary where the 

 temperature falls from T" to T still offers another difficulty of the 

 same 1-cind. Here we necessarily tind temperatures T' at which the 

 va[)Our branch of the binodal curve of T" intersects the liquid branch 

 of T' . If drops are formed at J", the composition ,vii,t of the liquid 

 belonging to the observed coexistence pressure can no longer ha 

 indicated. By flowing down and by distillation (the effect of capilla- 

 rity exceeds that of gravitation) the drops gradually pass over into 

 the liquid phase at T, if care is taken by means of the cock h (see 

 PI. I fig. J) and by adjustment of the pressure in /; (see PI. I fig. 1)) 

 that gas streams only into and not out of the piezometer, until finally 

 when we stir with open cock /,■ it a|)pears (hat equilibrium is 

 reached and the capillary contains \apour only. 



Iji order to further the disullation and the disappearance of the 



