Notes on this calculation

Silverster and Pitzer have the following numbers for equilibrium at 25C
      Delta_G0 = -9.0416 kJ gmol-1
      m_sat    = 6.146
      meanAC_moll = 1.008
This table is meant to run through that calculation. at 298.15. 
Thus Delta_G(298.15) should be 0.0. It's -0.00487 kJ/gmol -> very close =).