# Question to Figure 11.15
SOLUTION 1; -temp 25
EQUILIBRIUM_PHASES 1
 Calcite; O2(g) -0.68; CO2(g) -1.075 0
REACTION
 C7H8 1; 0.0128
SAVE solution 2
END
USE solution 2
EQUILIBRIUM_PHASES 1
 Calcite; Siderite 0 0; Goethite
REACTION
 C7H8 1; 3650e-7 in 10
USER_GRAPH
 -head x pCO2/10 Ca Fe*100 pH
 -axis_titles Distance/m mol/L pH
 -axis_scale y-axis 1e-3 9e-3 5e-4
 -start
 10 graph_x 150 * exp(0.2 * step_no /(8.5 * 0.38)) - 50
 20 graph_y 10^SI("CO2(g)") / 10, tot("Ca"), tot("Fe") * 100
 30 graph_sy -la("H+")
 -end
END