1904.] Properties of Solutions of Chloroform iii Water, etc. 395 



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° 

 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 convenient 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 commencement and termination of each determination of 

 vapour pressure, they are better adapted to their particular purpose 

 than a tap. In the course of our experiments, 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 vacuum was established by lowering 

 the mercury receiver, and for a long time was a source of annoyance. 

 We subsequently learned that the device had been first introduced by 

 Lord Rayleigh. At the end of an experiment, any air which has 

 collected is discharged by raising the mercury-holder, opening the 

 screw- clip shown, and allowing enough mercury also to pass through 

 to form a seal in the rubber tubing above the clip. 



The mercury-holder was suspended by means of a ring and loop of 

 wire attached around the bulb from a vertical rod, swivel, and hook, 

 possessing a slow screw movement in a block attached to a horizontal 

 rod fixed in a clamp, which could be moved up and down on a heavy 

 retort stand. For large movements, the clamp was slid up or down 

 the retort standard, and for fine movements the screw was raised or 

 lowered in its block. 



In using the apparatus, the two vertical tubes are first placed at the 

 same level, the mercury-holder is filled with mercury, and, with the 

 two glass stoppers out, the whole apparatus is filled with mercury, 

 the two stoppers are next inserted, enough mercury being left above 

 them to form a seal, and the mercury-holder is then lowered until the 

 two vertical tubes become evacuated. The receiver is then raised 



