LaSalle1940:
Generally, the absorption equation is attributed both to Kremser (1930) and Souders-Brown (1932). You'll find it more easily if you use Kremser's name.
A good plot of the Kremser-Souders-Brown equation is available in the 11th edition of GPSA's Engineering Data Book, Fig.19-48, page 19-31 (1999).
The theoretical basis of this equation is described in King, C. J.: "Separation Processes", Chapter 8 (McGraw-Hill, 1971). King also has a graphical plot of the equation that is set up a bit differently (using different parameters on a log-log plot) from the GPSA plot. King also provides the theoretical equation from which the plot was derived, in case you prefer iterative computer solution. However, you're still required to provide the K-value of the each of the components in the gas phase on each stage. This requires going to nomographs of the type Dick Russell has alluded to.
Also, note that the Kremser equation assumes constant L/(K.V) which is often not observed in practice for absorption of rich gases. Also, thanks to large temperature gradients, the K-values from top to bottom can vary a lot; therefore, one must use average values.
It turns out that finding good K-values is a lot more complex computation than solving the Kremser equation. That is why it is generally recommended to solve the problem more rigorously and use a general purpose process simulator. Dick Russell's PD-Plus is an excellent, inexpensive choice (
Finally, the theoretical basis of the Fenske equation is not quite appropriate for absorption calculations (constant relative volatility and equimolar flow, which apply more closely in distillation).