Liquid-Liquid Phase Behavior of Acetonitrile and Normal Alkanes

The mutual solubilities of binary mixtures of acetonitrile (ACN) and n-octane, n-hexane, n-heptane, and n-decane are examined. Here, we report the liquid-liquid phase behavior of binary mixtures in the temperature range of T = 295-380 K. As other ACN-n-alkane mixtures, the systems possess a partial miscibility with an upper (liquid-liquid) critical solution temperature (UCST), for the case of n-octane at T-c = 364.37 K. A detailed analysis of the experimental results together with a re-evaluation of data known from the literature presumes Ising criticality. Complementarily, the influence of water on the phase behavior is explicated in detail. The aim of the new measurements of the liquid-liquid equilibria (LLE) combined with the re-evaluation and analysis of the data from the literature is to investigate if the ACN-n-octane system may be an appropriate candidate to serve as a standard system recommended for calibration, evaluation, and checking experimental procedures and methods for the determination of LLE. The results indicate challenges for using this mixture for that. The crucial handling of ACN at dry conditions together with the nontrivial determination of cloud point temperatures at elevated temperatures (T = similar to 350-380 K) may foil or complicate an easy and handy procedure for proofing LLE results. The ACN-n-hexane system is more promising for this purpose.