Question

What is the upper critical solution temperature for a partially miscrible liquid - liquid binary system?

Answer 1

The word upper indicates that the UCST is an upper bound to a temperature range of partial miscibility, or miscibility for certain compositions only. For example, hexane-nitrobenzene mixtures have a UCST of 19 °C, so that these two substances are miscible in all proportions above 19 °C but not at lower temperatures.

Answer 2

The solution is miscible