General equations and schematic approach to calculations

The experimental data consists of measured thorium concentrations at different given H2SO4 concentrations in equilibrium with Th(S04)2 9H20(cr). The total measured aqueous thorium concentration is the sum of all the major aqueous thorium species (D.4) and the total experimental sulphate concentration is the sum of all the aqueous sulphate species (D.5). 

The AfG°/RT values of all the aqueous species in this system are known (Table D-6). The AjG° IRT value of Th(S04)2 9H20(cr) is the unknown which we need to optimise. The NONLINT-SIT program starts out with an estimated AfG° IRT (Th(S04)2 9H20, cr) value and calculates the total AfG, IRT of the solution phase (D.6) and the concentrations and activities of all of the species defined in the problem (Table D-6). Multiple iterations with different Af.G°/RT (Th(S04)2 9H20, cr) 

D The Gibbs energy minimisation and optimisation program, NONLINT-SIT 

The actual quantity minimised by NONLINT-SIT for this example is the penalty function  

W = molecular weight of water (18.016 g-mol ), Yi = activity coefficient of species i, 

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