T = 250 C Na+ = 50 mmol/kg Cl- = 50 mmol/kg balance on Na+ swap HS- for SO4-- HS- = 1 mmol/kg Cu+ = 10 umol/kg swap O2(g) for O2(aq) O2(g) = -50 log fugacity pH = 3 scope y slide log fugacity of O2(g) to 5 scope x slide pH to 11