STUDY OF THE PHYSICAL CHEMISTRY OF ANAESTHESIA 169 
In order to keep a constant temperature (in the case of the experiments carried 
out at body temperature) the upper portion of each tube, from about the middle of 
the wide part to the level of the stopper at the top, was encased in a hot-water jacket 
of the form shown in detail in Fig. 2, and omitted for clearness from Fig. 1. 
It was found convenient to use for the outer glass tubing of this jacket the 
largest size of a common variety of paraffin-lamp chimney, which measured 8 cm. in 
diameter above, bulged out as shown to 9 cm., and then narrowed below to 6 cm. 
The wider top and bulge were found very useful in facilitating the introduction 
and vigorous movements of the bar electro-magnet used as a stirrer in connexion with 
the iron stud (seen in Figs. 1 and 2, at the top of the mercury), which was dropped 
into each tube, and, during an experiment, agitated up and down so as to thoroughly 
mix the fluid under experiment, and so bring it into equilibrium more rapidly with the 
vapour in the space above it. 
The hot-water jacket was made watertight below by means of an india-rubber 
cork, as shown (Fig. 2) ; the rubber cork was also bored in each case for two narrow 
glass tubes, for the purpose of carrying water to and from the jacket. The two tubes 
carrying the water in stopped about 2 cm. above the upper surface of the rubber cork 
in each tube, so as to prevent blocking by mercury accidentally run over from the top 
when the inner tubes were being cleared out at the termination of a measurement. 
The outer ends of these two tubes were attached by means of narrow rubber tubings 
and a glass Y-tube to a bath of hot water, placed at a higher level, and a screw-down 
clip on each rubber tube regulated the flow until a thermometer placed in the 
corresponding hot-water jacket showed the desired temperature. A constant level of 
water was kept up automatically in the warm supply bath, and its temperature was 
regulated so as to lie 2-3 0 above that of the jackets. The two outflow tubes passed 
up, as shown, inside the jacket to the level of the ground in glass stopper, and their 
outside ends were connected by means of rubber tubing to the waste pipe. 
In Fig. 1 the upper portion of the left-hand tube is shown in section, and that 
of the right-hand one in outline. The ground in stoppers shown were found, when 
sealed with mercury, to be much more effectual against minute leakages, which 
entirely vitiate the results, than any form of tap, and they are also much more con- 
venient for introducing the solutions to be experimented upon, and for cleaning out 
the apparatus. Further, since they do not require to be operated between the com- 
mencement and termination of each determination of vapour pressure, they are 
better adapted to their particular purpose than a tap. In the course of our experi- 
ments, we also found it necessary to be able to dilute a solution with more of its 
solvent without allowing it to come in contact with any appreciable volume of air, 
and for this purpose found the stopper arrangement most convenient. 
The side tube shown at the lower end of each main tube was designed to trap 
air which was found to slowly leak in through the rubber pressure tubing, when a 
x 
