The total equilibrium concentration of a component in all forms or on the stationary phase divided by the total equilibrium concentration of the component in the mobile phase; also called the distribution coefficient or the partition coefficient in partition chromatography. In partition chromatography, K_c is used when the concentration in the stationary phase is expressed per unit volume of the phase (V_R = V_M + K_cV_S). In a solid stationary phase, K_g is used and is expressed per mass (weight) of the dry solid phase. In adsorption chromatography with a well-characterized adsorbent of known surface area, the concentration in the stationary phase is expressed per unit surface area.