Dissociation constant

In chemistry, biochemistry, and pharmacology, a dissociation constant (${\displaystyle K_{d}}$) is a specific type of equilibrium constant that measures the propensity of a larger object to separate (dissociate) reversibly into smaller components, as when a complex falls apart into its component molecules, or when a salt splits up into its component ions. The dissociation constant is the inverse of the association constant. In the special case of salts, the dissociation constant can also be called an ionization constant.

For a general reaction:

in which a complex ${\displaystyle {\ce {A}}_{x}{\ce {B}}_{y}}$ breaks down into x A subunits and y B subunits, the dissociation constant is defined

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