the Mutual Solubility of Liquids. 180 



similar results were afterwards obtained with ethane and 

 isopropyl alcohol, the latter substance being used as it came 

 from Kahlbaum, as the quantity was too small to admit of 

 efficient purification. 



The temperatures up to 50° C. were usually obtained by 

 means of a water-jacket. For higher temperatures, and also 

 sometimes for the lower ones (down to 30° C), a vapour- 

 jacket was used. The electromagnet which moves the stirrer 

 is outside this jacket. The boiling-substances used were 

 carbon disulphide, alcohol, chlorobenzene, aniline, and quino- 

 line. Aniline is the only one of these liquids that we had 

 difficulty in obtaining pure. Its boiling-point rose gradually 

 during distillation, and it was not easy to know which fraction 

 to select. There was, in consequence, some uncertainty as to 

 the relation of our aniline to that used by Ramsay and Young 

 in obtaining their pressure-temperature tables. We therefore 

 always used a small Geissler thermometer (Jena glass) in the 

 vapour-jacket, and were thus able to read the temperature 

 directly. Unfortunately the discrepancy between this direct 

 reading and the temperature as obtained from the tables of 

 Ramsay and Young is sometimes considerable. In some cases 

 there is no doubt that the direct reading is the correct one, 

 as, for instance, at 100° (J., for the thermometer could be 

 tested at that temperature. In the tables which follow 

 the temperatures are those read on the thermometers. 



The pressures were read (1) on an open mercury-manometer 

 up to 4" 5 atmospheres, (2) on a closed air-gauge reading from 

 3 to 30 atmospheres, and (3) on a closed air-gauge giving 

 readings above 25 atmospheres. The second gauge was 

 graduated by means of the first at a low pressure. A com- 

 parison made between gauges 2 and 3 showed a difference of 

 about | of an atmosphere. This difference we have since 

 found is due to the gradual oxidation of the mercury in the 

 third gauge. 



The irregularities in the differences near 130° C. and 

 150° C. are due to the difference between the gauges, and 

 probably also to the already mentioned uncertainty of the 

 temperatures. It will be seen from the table and the curves 

 in the diagram, that the pressure of the three phases is every- 

 where higher than for ether at the same temperature. The 

 difference is very small at the boiling-point, but increases 

 rapidly as the temperature rises. The three-phase pressure 

 remains, however, well below the sum of the vapour-pressures 

 of water and ether. Our result near the boiling-point agrees 

 with that obtained by Beckmann *. For the pressure at 

 * Nernst, Zeitschrift phys. Chem. viii. p. 134. 



