Pseudocritical constants

Pseudocritical rules provide a means to determine reduced properties for mixtures so that pure component corresponding states correlations may be used to estimate mixture properties. The most common pseudocritical rules are examined and shown to stem from a common base. Points of divergence as well as similarity are pointed out in tracing out the development of the rules. Reduction of all rules to simpler forms is made and criteria attached to allow one to determine when such simplifications are justifiable. All rules reduce to Kay's rule in certain limiting cases.