Coexistence Curve of the Triethylamine-Water System

Abstract

The coexistence curve of the system triethylamine‐water has been determined near its lower critical point. The observed critical temperature T_c is 18.33°C. There is evidence of a small horizontal portion of the coexistence curve, which extends from 0.559 to 0.657 volume fraction water, or from 0.907 to 0.936 mole fraction water, though the evidence is not absolutely certain. On the other hand, our results exclude the possibility of an anomalous phase transition in the concentration interval from 0.35 to 0.90 mole fraction water where, according to a report by J. E. Mayer, such an anomalous transition may occur. Outside the small horizontal portion the coexistence curve shows the same cubic behavior [(T–T_c)^⅓, or better (T–T_c+0.007)^⅓, proportional to the difference of the volume fractions of the phases in equilibrium] as do coexistence curves of systems with upper critical points, but is much flatter, the proportionality factor having a smaller absolute value.