Automated apparatus for the rapid determination of liquid-liquid and solid-liquid phase transitions

Abstract

An automated app. developed for the detn. of liq.-liq. and solid-liq. equil. temps. with a resoln. of 1 mK and a traceable accuracy of 0.01 K is described. The amt. of light transmitted through six sample cells placed in a computer controlled thermostat is recorded at heating or cooling rates from 0.075 to 15 K h-1. The construction does not require expensive optic equipment like lasers, glass fiber optics or photomultipliers, but is based on light emitting diodes (LED) as light sources and light dependent resistors (LDR) or photodiodes as detectors. As shown by the discussed examples, the instrument has a wide range of possible applications from the investigation of simple one-component and binary systems to the study of the complicated phase behavior of surfactant solns.