The operating line (magenta) represents the mass balance:
Rearranging the mass balance to solve for
is the mole ratio of impurity in the inlet liquid stream (ppm);
is the mole ratio of impurity (ppm) in the gas stream that corresponds to
, which is the mole ratio of impurity in the liquid stream (ppm);
is the mole ratio of impurity in the outlet gas stream (ppm);
is the liquid molar flow rate (Mmol/h); and
is the gas molar flow rate (MMol/h).
The equilibrium line (orange) is calculated using Henry's law:
is Henry's constant (atm/mole fraction) and
is pressure (atm).
Henry's constant is calculated from
, its value at standard temperature
is the activation energy (J/mol),
is the gas constant (J/(mol K)) and
has units of atm/mole fraction.
 P. C. Wankat, Separation Process Engineering: Includes Mass Transfer Analysis
, 3rd ed., Upper Saddle River, NJ: Prentice Hall, 2012.