383 
bring about a sufficient vacuum'). When the whole apparatus had 
been exhausted, the balb with water was broken by cooling with 
carbonic acid alcohol, that with ether by heating, and the contents 
of both were condensed in C and D by means of liquid air. The 
air dissolved in the liquid in the bulbs could then be removed by 
the cocoa-nut carbon. Then the mercury which had been boiled in 
vacuo was conveyed from G in small drops through the constriction 
H into the Cailletet tube, which was then screwed into the pressure 
cylindre in the known way after having been separated from the 
filling apparatus at F. 
In some experiments the stem of the bulb filled with water was 
put into the opening of the plug of cock A, and broken after the 
evacuation of the apparatus by rotation of A. This method of working 
proved very convenient for the realisation of concentrations of definite 
amount. Then there was no necessity for the bulb to be filled so 
far with water as is necessary for bursting in consequence of solidi- 
fication and the weighing of a definite quantity of substance was 
rendered a great deal easier thereby. 
At last the Cailletet tube was surrounded with a jacket, in which 
nitrobenzene was electrically heated till it boiled under varying 
pressures *). 
4. Discussion of the results. 
In the cited paper the shape of the plaitpoint curve in its 7z-, 
and its P,7-projection was examined by Prof. van per Waats. It 
then appeared that after some modification fig. 43 of the series of 
contributions mentioned can account for the phenomena which appear 
1) Cf. eg. These Proc. XIII p. 831 and fig. I on p. 830. 
2) To obtain constant temperatures I made use-of a steam-jacket, which is 
different from the one generally used. A wide tube is provided with a smaller one 
on either side which are closed with rubber stoppers prepared for high tempera- 
tures. On the constriction at the bottom rests an inner tube, which ends about 
10 cm from the upper constriction. The stopper on the bottom side has one 
perforation for the Cailletel tube, which is entirely inside the inner tube, two for 
the supply of the electric current, and an aperture through which a tube is put 
for sucking up and letting out the boiling-liquid. The heating is effected by means 
of a nickeline wire adjusted in the inner tube and wound spirally. The boiling 
liquid rises in the inner tube, condenses in the upper part of the outer tube, and 
flows down in it. In the inner tube two branch apertures have been made close 
to the bottom to keep the liquid at the same level inside and outside the inner 
tube. A glass tube through the stopper at the upper end brings about the con- 
nection with water jet pump, manometer, pressure regulator etc. If we proceed 
in this way there is no difficulty whatever in keeping the temperature constant for 
any length of time. 
