Thermochemical data from P-T brackets

Thus if the corrections from P and T to 1 atm. and 25°C could be carried out without error, and if the free energies of all but one of the reacting phases were perfectly known, then the free 

Naturally the reduction to standard conditions cannot be made without error, although if heat capacities are known there is no reason why this source of error should not be negligible. Similarly, the free energies of all the other phases in the reaction cannot be assumed to be perfectly known. Nevertheless this procedure has proved very useful so far in tracking down major inconsistencies in the thermochemical data of groups of minerals. The major limitation of this method as a source of data for individual 

Nevertheless, I believe that this property of experimental temperature brackets of providing very tight windows for free energies of reaction will play a major role in reducing the uncertainties in thermochemical data. This will be discussed further in the next section. 

The problem of how best to report the uncertainty of a free energy deduced from P-T brackets is a difficult one. My present inclination would be to follow the procedure of Bird and Anderson (1973) though using the Monte Carlo technique to make the procedure simpler, and to correct for the covariance of phases in the reaction before doing this calculation. 

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