Reversing the X-A and B-X arrows amounts to multiplying the
forest’s term by (kA-X kX-B )/(kX-A kB-X Þ) In view of the Onsager relations, this value does not depend on X, but only on A and B; in fact, it is the equilibrium constant KA-...-B . If several X or Y or Z occur, the reasoning is the same. Consequently, every term in the numerator of AB is in that proportion to the corresponding term in the numerator of BA, and the fixed proportion for all s translates directly to the time domain: