Fugacity in Equilibrium Calculations

Assuming now that we have access to tables of fugacities or fugacity coefficients for a range of P, T conditions, we now have a means of conveniently evaluating the integral V dP at any temperature T for a fluid species such as H2O or CO2. A large and important class of mineral reactions involves only solid minerals and either water or CO2, such as 

Therefore we need only split the volume integral in our previous equations (Chap-, ter 8) into two parts—one for the solids and one for the fluid. Suppose we have a reaction 

The pressure integral for the solids is then evaluated using the constant AV approximation, and that for the fluid is evaluated using fugacities. Thus 

For the muscovite breakdown reaction given above, we can start with equation 

Since we have a, b, and c Maier-Kelley coefficients for water and other fluids as well as for solids, the temperature integral is evaluated as before. Now 

---