Critical behavior of the density, heat capacity, and refractive index for triethylamine + water

We have measured the mass density as a function of temperature for a mixture of triethylamine + water of critical composition in the one-phase region below the lower critical solution point. We find an anomalous decrease in density near the critical point of about 10−3 of the density. The functional form predicted by renormalization group theory represents the data within error. We have reanalyzed the heat capacity measurements of Thoen, Bloemen, and Van Dael [J. Chem. Phys. 68, 735 (1978)] on this system and have shown thermodynamic consistency with the density results. We have reanalyzed the refractive index measurements of Beysens and Bourgou [Phys. Rev. A 19, 2407 (1979)] on this system and have shown that these data do not have the same critical behavior as the density. We have calculated the amplitude of the correlation length divergence from the density results and found reasonable agreement with light scattering results.