Cloud-point measurements for the mixture tertiary butyl alcohol, secondary butyl alcohol, and water

Abstract

Cloud point measurements are presented for the ternary mixture of tertiary butyl alcohol (tBA), secondary butyl alcohol (sBA), and water. At a zero tBA concentration the system displays a large immiscibility gap, but with an increasing proportion of tBA, the gap pinches off at a critical double point to a closed loop and a lower gap, then the loop shrinks and disappears at a hypercritical point, leaving only the lower gap. This behavior is shown to be semiquantitatively similar to the behavior of sBA/water with increasing pressure. If a pseudobinary assumption is made, the shape of the cloud-point curves can be shown to be qualitatively similar to coexistence curves in binary mixtures, with an exponent of β ≃ 1/3. Near the critical double point this exponents appears to double.