In a publication of 1909 (see reference below), the Danish scientist Soren P.L. Sörenson discussed the inadequacy of measuring acidity by the total amount (normality) of acid additions to a particular solution. The added amount of acid would not necessarily be a true measure of its dissociation, depending on chemical interactions with other chemical species. Sörenson proposed that the actual degree of acidity should be rationally measured by hydrogen ion concentration and proposed the pH scale for expressing the hydrogen ion concentration as detailed in the quote below:

"I will explain here that I use the name "hydrogen ion exponent" and the designation P_H for the numerical value of the exponents of this power."

Sörenson reportedly was involved in work testing the acidity of beer and the pH symbol rooted in the French "pouvoir hydrogene" (power of hydrogen).

The pH variable is obviously a very important variable in aqueous corrosion studies and often monitored as a process variable, together with corrosion sensor signals.

References/Literature:

S.P.L. Sörenson: Biochemische Zeitschrift, 21, 1909, pp.131-200.

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