On the Limit of the Liquid State. 



over 300 atmospheres is required, these wide manometers are very apt 

 to burst, so that for high pressures a narrower tube must be used. 



The first work undertaken was to ascertain without doubt the 

 critical point of pure anhydrous ethyl alcohol, and this was done as 

 follows : — The alcohol sold as absolute by the makers was fractionated, 

 and the middle third taken. This was placed in a retort with freshly 

 burnt lime, and an inverted condenser adapted to it. After it had 

 been boiling for some time, the end of the condenser was fitted with a 

 drying tube of calcium chloride, to prevent moisture from entering. 

 The cohobation was continued for a week, and the alcohol then dis- 

 tilled off. The first fifth was rejected, as was also the last. The 

 receiver was a small flat-bottomed flask, which is shown fitted up for 

 use (after it was filled with alcohol) in the front of the drawing. It 

 was arranged as a wash-bottle, having the tube for the entrance of air 

 connected with a small vitriol tower, and an india-rubber ball, fitted 

 with valves, to apply pressure. The exit tube was adapted to the 

 experimental tube by a piece of india-rubber tubing, through which 

 was forced a piece of capillary tubing. When the apparatus was 

 to be used in experiment the arrangements were made as follows : — 

 The cap with the pressure-screw was first fitted on next the experi- 

 mental tube, with its point sealed up, and the whole filled up to the 

 top of the manometer branches with mercury. The manometers were 

 now placed in position and screwed tight. The apparatus was then 

 tilted so as to raise the point of the experimental tube, keeping it, 

 however, above the level of the lower ends of the manometers, and 

 the point then broken off. If the point were below the level of the 

 manometers some gas might escape. The wash-bottle arrangement is 

 then fitted to the experimental tube and the ball compressed. Alcohol 

 is driven over and escapes by the capillary tube, and this is continued 

 till the inside of the tube has been well washed and all impurities 

 removed. The capillary tube is then withdrawn, when the small 

 puncture in the india-rubber at once closes itself. The screw of the 

 pressure apparatus is then retreated, and when sufficient alcohol is 

 made to enter the apparatus, the joint is undone and the whole wash- 

 bottle arrangement placed under a bell-jar over oil of vitriol for use 

 another time, the india-rubber tube being clipped. The screw is then 

 further retreated to leave a small air-space over the alcohol, which is 

 then boiled and the point sealed, and the tube placed in the air- 

 bath. A mercury regulator, such as I have described elsewhere, was 

 sometimes used when the temperature was required to be constant for 

 long. 



The following tables contain some of the series of observations on 

 alcohol, and are given to show the numbers obtained when the work is 

 done with every care. The alcohol used was different in each case, so 

 that slight variations in the averages may be due to differences in the 



