Sørensen, Søren Peter Lauritz

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(b. Havrebjerg, Slagelse, Denmark, 9 January 1868; d. Copenhagen, Denmark, 12 February (1939)


The son of a farmer, Sørensen was educated at the high school at Sorø and entered the University of Copenhagen at the age of eighteen. He planned to study medicine; but under the influence of S. M. Jorgensen, an important investigator of inorganic complex compounds, he chose chemistry for his career, While at the university Sørensen received two gold medals, the first for a paper on the concept of the chemical radical and the second for a study of strontium compounds. While working for the doctorate he assisted in a geological survey of Denmark, acted as assistant in chemistry at the laboratory of the Danish Polytechnic Institute, and served as a consultant at the royal naval dockyard. His doctoral dissertation (1899) concerned the chemistry of cobaltic oxides. Thus most of his training was in inorganic chemistry.

All this was changed when, in 1901. Sørensen succeeded Johann Kjeldahl as director of the chemical department of the Carlsberg Laboratory in Copenhagen, where he remained for the rest of his life. Kjeldahl had worked on biochemical problems, and Sørensen continued this line of inquiry. His investigations can be divided into four classes: synthesis of amino acids, analytical studies, work on hydrogen ion concentration, and studies on proteins. The first, beginning in 1902, was concerned with synthesis of such amino acids as ornithine, proline, and arginine. The following year the demonstrated that the Kjeldahl method for determination of amino nitrogen was of much greater generality than its discoverer had claimed.After working out the Formal titration method for analysis of proteins, he turned to a study of the effects of such buffers as borates, citrates, phosphates, and glycine on the behavior of proteins, with especial attention to enzymes.

This work led Sørensen to study the at quinhydrone electrodes and the effect of ion concentration in the analysis of proteins. His most notable suggestion came from this work. In 1909 he investigated the EMF method for determining hydrogen ion concentration and introduced concept of pH as an easy and convenient for expressing this value. He was particularly interested in the effects of changes in pH on precipitation of proteins. After 1910 Sørensen made many studies on the application of thermodynamics to proteins and the quantitative characterization of these substances in terms of laws and constants. In much of this work he was assisted by his wife, Margrethe Høyrup Sørensen. They studied lipoproteins and the complexes of carbon monoxide with hemoglobin and in 1917 succeeded crystallizing egg albumin for the first time.

Sørensen always encouraged visiting scientists at the Carlsberg Laboratory to work on medical problems. He also was active in chemical technology, contributing to the Danish spirits, yeast, and explosive industries. He received many honors from both scientific and technological societies. Sørensen retired in 1938 after a period of poor health and died the following year.


I. Original Works. There is a complete bibliography in Kolloidzeitschrift, 88 (1939), 136–139. The pH concept is presented in “Enzymstudien. II . Über die Messung und die Bedeutung der Wasserstoffionkonzentration bei enzymatischen prozessen,” in Biochemische Zeitschrift, 21 (1909), 131–200. The isolation of crystalline egg albumin is described in “On the Composition and Properties of Egg-Albumin Separated in Crystalline Form by Means of Ammonium Sulphate,” in Comptes rendus du Laboratoire de Carlsberg, 12 (1917), 164–212.

II. Secondary Literature. Biographical sources are the Sørensen memorial lecture by E. K. Rideal, in Journal of the Chemical Society (1940), 554–561: K. Linderstrøm-Lang, “S. P. L. Sørensen,” in Kolloidzeitschrift, 88 (1939), 129–136; and Edwin J. Cohn, “Søren Peter Lauritz Sørensen,” in Journal of the American Society,61 (1939), 2573-2574.

Henry M. Leicester