Note 553 — Chapter XV · OXIDATION AND REDUCTION. II. OXIDATION BY OXYGEN, PERMANGANATES, ETC.; OXIDATION OF ORGANIC COMPOUNDS

These constants are calculated from data given in Wilsmore's tables (loc. cit.) on the solution tension of hydrogen. Hydrogen, at 18° under one atmosphere pressure, produces a potential of εH2, H+ = +0.277 (see p. 261, in regard to the sign) against a solution containing hydrogen-ion in a concentration [H+] = 1 (see the table at the end of this chapter). Now, there must be some concentration of hydrogen-ion, which we will call [C], with which hydrogen at 18° and 760 mm. pressure is directly in equilibrium, with the potential 0. For any concentration of hydrogen-ion [H+], other than [C], a potential is produced according to εH2, H+ = 0.0575 log([H+] / [C]). If we insert into this equation the values [H+] = 1 and the potential ε = +0.277, and if we solve the equation for [C], we find [C] = 1.52E−5. That is the concentration of H+, with which hydrogen of one atmosphere pressure at 18° is directly in equilibrium. Since under these conditions of temperature and pressure [H2] = 1 / 23.9 mole, we have for the condition of equilibrium [H+]2 / [H2] = K : (1.52E−5)2 : (1 / 23.9) = 5.55E−9 = K.