an equation describing the oxygen saturation curve of hemoglobin:

where
R is the fractional saturation of hemoglobin with oxygen,
K1,
K2,
K3, and
K4 are the stepwise intrinsic association constants for the four oxygen-binding sites, and
pO2 is the partial pressure of oxygen. For a generalized form of this equation see
Bjerrum formation function. [Defined by Gilbert Smithson Adair (1896 — 1979), British biophysicist, in 1925.]