Critical point measurements of four pyridines

The critical temperatures and pressures of 2-, 3-, 4-ethylpyridines, and 2-methyl-5-ethylpyridine have been measured. The critical properties of 3- and 4-ethylpyridines are very close while those of 2-ethylpyridine noticeably differ from them, which correlates with the normal boiling points of these compounds. The experimental critical constants of the pyridines investigated have also been compared with those calculated using the group (bond) contribution methods of Wilson and Jasperson, Marrero and Gani, Hukkerikar and co-workers, Marrero-Marejón and Pordillo-Fontdevila. The acentric factors of the pyridines have been calculated.