Non-linear continuous cooling experiments were performed on both orthopyroxenes to test the ability of the Mueller rate equation (Mueller, 1967, 1969) to correctly predict the evolution of ordering. The crystals were cooled from 850°C to 250°C at an average rate of 13°C/day. The frozen site occupancies could be fully reproduced by the calculated ordering paths when the Mueller equation was run with the temperature dependencies of KD given above and Arrhenius parameters for kdis, taken from Kroll et al. (1997) and slightly adjusted within their error limits.
Site refinements were also performed under the assumption that an error of ±1% total Fe had occurred in the microanalysis. This resulted in In (KD) lines which almost coincide for En49Fs51, but are clearly different for En81Fs19. Consequently, the error of calculated cooling rates is negligible for En49Fs51, but becomes significant for En81Fs19.