A plot of 1/P - 1/3 versus T/h
predicts a straight line, the intercept and slope of which permit
determination of Po and the molar volume (if the lifetime is
known). Shown below is such a plot
(termed a Perrin-Weber plot) for protoporphyrin IX associated with
apohorseradish peroxidase - the viscosity of the solvent is varied by addition
of sucrose.