The buffer mechanism for the calcion concentration and the determination of calcion buffer values.

Abstract

The calcion concentration of aqueous systems is regulated by calcion buffers. They are electrolytes which resist the change in calcion concentration upon addition or removal of calcium salts. The calcion concentration is stabilized in the presence of mixtures of weak acids and their salts which react to form insoluble normal calcium salts and soluble intermediate calcium salts. The calcion concentration may be expressed in terms of calcion buffers by applying the law of mass action to the general form of the above buffering equations. Where [H A] and [B A] are the concentrations of the calcion buffering acid and salt respectively; Y1 and Y2 their activity coefficients at the calculated ionic strength; n is the ratio of the valence of calcium to that of the acid and K is an equilibrium constant. Expressed in logarithmic units, This expression enables the derivation of the calcion buffer value, P, the unit of which is the number of grain equivalents of calcium salt or acid necessary to change the calcion concentration one unit of pCa and is given by, The calcion buffer value expressed by equivalent equations shows that at any given hydrion concentration the calcion buffer value is directly proportional to the total concentration of buffer acid or salt. The calcion buffer value is independent of the nature of the weak acid provided it forms an insoluble normal calcium salt. The calcion buffer value of the carbonates of normal blood is sum of the separate calcion buffer values. The maximum calcion buffer value is attained when there are 0.586 parts of buffer salt and 0.414 parts of free buffer acid.