A MODIFIED EBULLIOMETRIC METHOD FOR HIGH-BOILING SUBSTANCES - VAPOR-PRESSURES OF 2-CHLOROBENZONITRILE AND 4-CHLOROBENZONITRILE AT TEMPERATURES FROM 380-K TO 490-K

A modified ebulliometer and an apparatus based on comparative ebulliom etry have been assembled for vapour-pressure measurements on high-boil ing substances with melting temperatures as high as about 400K. The va pour pressures of 2-chlorobenzonitrile and 4-chlorobenzonitrile in the approximate temperature range: 380 K through 490 K, have been determi ned with estimated accuracy better than 0.04 K in the temperature and 0.1 per cent of the measured pressure value. The results thus obtained were correlated by the Antoine and Cragoe-Marks equations. Experiment ally determined freezing temperatures of the two chlorobenzonitrile is omers and the calculated relative volatility of their binary mixture a s a function of temperature are also reported.