The Determination of Hydrogen Ions

of a cell free from liquid junction potential, consisting of a hydrogen electrode and a reference electrode, should be given by 

If the usual value for Er u of the reference electrode is employed in this equation to derive pH s, the results are found to be inconsistent with other determinations that are thermodynamically exact. A possible way out of this difficulty is to find a value for such that its use in equation (2) gives pH values which are consistent with known thermodynamic dissociation constants. For this purpose use is made of equation (29) of Chap. IX, viz., 

The conclusions reached from this w ork may be stated in terms of the potentials of the reference electrodes for example, the value of Eref, of the 0.1 N KCl calomel electrode for the purpose of determining pH s by means of equation (2) is 0.3358 volt at 25°. In view of possible variations in the salt bridge from one set of experiments to another, it is preferable to utilize these potentials to determine the pll values of a number of reproducible buffer solutions (cf. p. 410) which can form a 

TABLE LXII. STANDARDIZATION OF pH VALUES OF REFERENCE SOLUTIONS 

Whatever form of electrode vessel is employed, the fundamental principle of the operation is always the same. The hydrogen gas is adsorbed by the finely divided platinum and this permits the rapid establishment of equilibrium between molecular hydrogen on the one hand, and hydrogen ions in solution and electrons, on the other hand, thus 

---

Clark, W. M. (1928). The determination of hydrogen ions an elementary treatise... 

Ref [i] Clark WM (1928) The determination of hydrogen ions. The Williams Wilkins Comp, Baltimore, p 37... 

Clark, W. Mansfield. The Determination of Hydrogen Ions. The Williams Wilkins Company, Baltimore. 1928. 

It is assumed that the student is familiar with the meaning of this expression. If not, he is referred to W. M. Clark s book. The Determination of Hydrogen Ions, Williams and Wilkins, 1920. 

The quinhydrone electrode has been adapted for pH measurements in non-aqueous media, such as alcohols, acetone, formic acid, benzene and liquid ammonia. For the determination of hydrogen ion activities in solutions in pure acetic acid a form of quinhydrone electrode involving tetrachloroquinone (chloranil) and its hydroquinone has been used. ... 

For details concerning the preparation of buffer solutions, see Clark, The Determination of Hydrogen Ions, 1928, Chap. IX Britton, Hydrogen Ions, 1932, Chap. XI Kolthoff and Rosenblum, Acid-Base Indicators, 1937, Chap. VIII. 

For further details concerning the operation of this cell, and much else on the determination of pH, see W M. Clark s The Determination of Hydrogen Ions/ 3rd ed The Williams and Wilkins Co., Baltimore, 1928. 

Daniele, S., Bragato, C. and Baldo, MA. (2006) A steady-state voltammetric procedure for the determination of hydrogen ions and total acid concentration in mixtures of a strong and a weak monoprotic acid. Electrochimica Acta, 52, 54-61. 

In this presentation, we review results which directly confirm the validity of the proposed SDP mechanism. By using cyclic voltammetry simultaneously with the determination of hydrogen ion or sodium ion concentration in the electrolyte, we proved that H+-ejection and Na+-ejection occur upon electrochemical oxidation of the polymer. The results demonstrate, in addition, a voltage controlled ion exchange mechanism. 

In the determination of hydrogen ion concentration in a weak acid solution, use of the quadratic equation can sometimes be avoided using a method known as successive approximation. Consider the example of a 0.0150 M solution of hydrofluoric acid, (HF). The K for HF is 7.10 X 10 . To determine the hydrogen ion concentration in this solution, we construct an equilibrium table and enter the initial concentrations, the expected change in concentrations, and the equilibrium concentrations of aU species ... 

---