Regression analysis of nonlinear Arrhenius plots: an empirical model and a computer program.

The rates of most physical, chemical and biological processes vary with temperature and numerous instances have been reported in which Arrhenius plots of the experimental data appear to consist of two straight line segments joined by a relatively sharp break. An empirical model, based on a general hyperbola, is shown to be applicable to such systems; a nonlinear regression program is described which facilitates fitting of this function to experimental data which show either broad or sharp transitions. The program yields best estimates and standard errors of the temperature and ordinate value at the transition, and the two activation energies.