S.P.L. Sørensen

Søren Peter Lauritz Sørensen (Havrebjerg, January 9, 1868-Copenhagen, February 12, 1939) was a Danish chemist whose greatest contribution was to introduce the hydrogen potential (pH) scale.

After earning his PhD from the University of Copenhagen, he was head of the chemistry department at the prestigious Carlsberg Laboratory in Copenhagen. While working at the Carlsberg Laboratory, he studied the effect of ion concentration on proteins, and why the H+ ion was particularly important. In 1909 he introduced the pH scale as a simple way of expressing pH, defining it as the negative logarithm of the hydrogen ion concentration. In the article in which he introduced the scale (using pH notation), he described two new methods for measuring pH. acidity: electrodes and the comparison of the colors of samples by means of a preselected set of indicators. He was in charge of obtaining the formula to be able to handle whole numbers in pH.

It is also known by the formol titration or Sørensen method.

Sørensen focused his scientific work in the field of biochemistry by directing the chemical laboratories of the Carlsberg brewery. His research focused on the incidence of acidity in the functioning of fermentation enzymes. In the publication called Enzyme Studies II The Measurement and Meaning of Hydrogen Ion Concentration in Enzymatic Processes in 1909. Sørensen states that it was inappropriate to calculate the degree of acidity or alkalinity by the amount of acid or alkalinity added to a solution. The amount of acid added was not necessarily a true measure of its dissociation, it depends on its chemical interaction with other chemicals. Sørensen's interest in determining the degree of acidity or alkalinity of a solution arose from the knowledge that this measurement influenced enzymatic processes, such as the rate at which enzymatic cleavage occurred. If this value was designated according to the amount of acid or base added, the dissociation constant of these substances was unknown, so the values obtained could not be reliable since these substances in solution do not dissociate in the same way, this theory had already been been proposed by Arrhenius speaking of electrolytic dissolution. Therefore, the concentration of Hydrogen ions depends not only on the amount of acid but also on the acid involved in the process.

He also proposed that the concept pH understands the nature of matter as discontinuous, when referring to the hydrogen ion in aqueous solutions. The general idea of discontinuity states that "any macroscopic portion of matter is made up of an enormous amount of particles animated by constant motion." Molecular displacements are linked to the energy of the molecules. Kinetic energy is directly related to the displacement of molecules; Potential energy, on the other hand, involves interactions between molecules that depend on the average distance between them. The macroscopic properties of matter are manifestations of the average behavior of all the particles of the considered system.