( 100 ) 



attention to, and it was not necessarv to use a more accurate in- 

 strument. Tiiis slight influence, which had been expected beforehand 

 from the theory and in connection with the experiments before- 

 mentioned, made it necessary to make the observations near the 

 temperature of complete mixture. Here the difficulty presented itself, 

 that the heat which would be developed by compression, might be 

 the cause that the temperature, which had first been below the 

 temperatuie of complete mixture, would rise above it. In this case 

 mixture would not be the direct consequence of tlie pressure. There- 

 fore it was of great importance to make an arrangement by means 

 of which it would be possible to keep the temperature round the 

 glass-tube constant for a considerable time: for in this way it would 

 be possible to remove the disturbing influence mentioned before. The 

 attempts to get a suitable thermostat, led to the following arrange- 

 ment agreeing iu many respects with the one described by "W.Watson 

 (Phil. Mag. Vol. 44 July 1897): a glass cylinder, 30 cM. high and 

 with a diameter of 5,5 cM., is closed on both ends with caoutchouc 

 stoppers. These stoppers are pierced in the middle, so that a glass 

 cylinder of the same height as the former and with a diameter of 

 2^ cM., can be placed concentrically with the other. 



The annular cylindric vessel obtained iu this way, is placed so 

 as to have its axis vertical. Two holes made in the higher stopper, 

 give an opportunity of adjusting two glass tubes. One of these is 

 closed with a tip and serves to bring the liquid into the vessel. 

 The other is (the glass tubes being in close contact) connected by 

 means of a rubber tube with another glass tube placed vertically, 

 which leads tlirongh a cooling-apparatus, and is bent horizontally 

 just above it. It leads further to a T shaped piece to which are 

 fastened 1°. an open manometer 2". another T shaped piece. One 

 arm of the latter T shaped piece has a rubber tube with a squeezer. 

 This squeezer is so constructed that by means of a screw the ad- 

 mission of air can be nicely regulated or entirely stopped. The 

 other arm leads to two large closed bottles, having together about 

 40 L. contents, and from there to a rubber tube (with a squeezer), 

 which brings about the connection with a waterairpump. In this 

 way the vessel is connected with a lai'ge space, in which the 

 pressure can be lowered. The regulating of this pressure, read 

 bv means of the open manometer, can be easily done by the two 

 squeezers mentioned. Then a small quantity of mercury is first 

 brought into the vessel, enough to cover the bottom, and to 

 preserve the caoutchouc in this way, and on it a quantity of aethyl- 

 alcohol, which can be made to boil under various pressures. The 



