Blood : a study in general physiology / by Lawrence J. Henderson.

  • Lawrence Joseph Henderson
Date:
1928
Catalogue details

Licence: In copyright

Credit: Blood : a study in general physiology / by Lawrence J. Henderson. Source: Wellcome Collection.

    67/434 (page 41)
    Applying the law of mass action we obtain the equation (H+HHCO,-) (H2co3) This is exact if the quantities in parentheses are taken as representing the true thermodynamical concentrations or activities of the respective substances. Also, in accord¬ ance with Henry ?s law, we may write the equation (H2COs) = y,*A*c*(pC02), (2) where pC02 represents the partial pressure in milli¬ meters of mercury of carbon dioxide in equilibrium with a solution, c, the molal concentration of free carbonic acid in the solution when pC02 — 1, yi the activity coefficient of carbonic acid, and A that of water in the solution. If a be the absorption coefficient of carbon dioxide we have a C ~ 22.4 X 760 ‘ Also, if bicarbonate be present in the solution we have (HC03-) = y2 • [BHC03]. (3) Here [BHC03] as usual represents the ordinary molal concentration of bicarbonate and y2 the activity coefficient of the bicarbonate ion in the solution. Combining equations 1, 2, and 3, and rearranging terms, we finally obtain an equation which exactly ex¬ presses the hydrogen ion concentration of a buffer mix¬ ture of carbonic acid and bicarbonate. i-tt+1 _yyA-fc c • (pC02) /4\ L J y2 [BHC03] The activity coefficients yx, y2, and A are variables; their values depend upon the nature and the concentration of every substance present in the solution and for the pres¬ ent they cannot in general be accurately estimated. Valu¬ able information concerning these quantities and the equi¬ librium in question may be found in a recent paper by