The pH scale, invented by Soren Peter Lauritz Sorensen, "has become so much a part of scientific literature and its influence so important a factor in considering biological problems that one wonders how theories of acidity and alkalinity were ever formulated without a knowledge of Sorensen's fundamental conceptions," A. J. Curtin Cosbie commented in Nature. Potential of hydrogen, or pH, is a simplified measure of the acidity of any given mixture. Though of immense value to scientist and layman alike, the pH scale is only one of Soren Sorensen's many achievements in a career devoted to the application of classical physico-chemical methods to the new realms of biochemistry and specifically to fermentations problems. His research on enzymes and proteins in particular--for which the invention of the pH scale was merely a methodological improvement--were invaluable, laying the groundwork for precise and thorough studies of these nitrogenous compounds.

Sorensen was...