Coexistence curve of the ionic binary mixture tetra-n-butylammonium picrate in 1-dodecanol

The coexistence curve of the ionic binary mixture tetra-n-butylammonium picrate in the low dielectric solvent 1-dodecanol is measured in the reduced temperature range 4.2×10−5<(Tc −T)/Tc<4.2×10−3, with Tc the critical temperature. The asymptotic critical exponent β is found to be close to the 3-D Ising value with one negative correction-to-scaling term. However, when the data are corrected for a small drift of Tc, no cross-over behavior is observed in the studied temperature range. The mean diameter can be fitted by a simple linear law showing no anomaly within the accuracy of our measurements.