(b. Hamburg, Germany, 6 September 1858; d. Königsberg, Germany [now Kalingingrad, U.S.S.R.], 9 October 1922),
Cohn, who published under the name of Lassar-Cohn, studied chemistry at Heidelberg, Bonn, and Königsberg. He was Privatdozent (1888) and then professor of chemistry (1894–1897) at Königsberg, at Munich (1897–1898), and again at Königsberg (1902–1901). Cohn was associated with various industrial firms throughout his career; he conducted researches in organic and physiological chemistry and in chemical technology.
The most elaborate of Cohn’s investigations was the isolation of the acids in ox and human bile by means of saponification, acidification, and solvent extraction (1892–1898). By oxidizing cholic and dehydrocholic acids Cohn prepared bilianic and isobilianic acids in 1899. From the latter he obtained another oxidation product called cilianic acid. The understanding of the structures of the bile acids and their oxidation products came with the work of Heinrich Wieland in 1912.
Cohn also studied the electrolysis of organic potassium salts (1889) and prepared several halogenated derivatives of salicylic acid (1905). He developed an improved nitrometer for the determination of nitrogen by the Dumas method (1901) and invented a new saccharimeter (1922). He also published papers dealing with the utilization and disposal of chemical waste materials from industrial processes. Cohn made a careful study of the sulfite waste liquor from cellulose factories, proposing that the waste matter, instead of polluting rivers, could be made beneficialk to crops. After chemical treatment to reduce acidity, it could be pumped into canals and thence to irrigated fields.
Cohn was a successful writer of popular books on chemistry. Two books were especially widely read: Die Chemie im täglichen Leben (1896), which appeared in twelve German editions and was translated into many languages, and Einführung in die Chemie in leichtfasslicher Form (1899), which appeared in seven German editions. Both books were written for the general public, the former stressing the practical applications of chemistry, the latter the theoretical principles. His Arbeitsmethoden für organisch-chemische Laboratorien (1891) was a valuable compilation of all the methods for particular laboratory operations in organic chemistry: drying, distillation, extraction, filtration, molecular weight determination, sulfonation, halogenation, nitration, and so forth. The book was widely used in Germany and was also successful in its English translations.
I. Original Works. Cohn’s Arbeitsmethoden für organisch-chemische Laboratorien (Hamburg, 1891; 5th ed., Leipzig, 1923) appeared in two English versions: A Laboratory Manual of Organic Chemistry, translated by Alexander Smith (London, 1895) and Organic Laboratory Methods, translated by Ralph E. Oesper and edited by Roger Adams and Hans T. Clarke (Baltimore, 1928). Die Chemie im täglichen Leben (Hamburg-Leipzig, 1896; 12th ed., Leipzig, 1930) was translated by M. M. Pattison Muir as Chemistry in Daily Life (London, 1896; ed., 1917). Cohn’s Praxis der Harnanalyse (Hamburg, 1897) had nine German editions and an English translation by H. W. F. Lorenz, Praxis of Urinary Analysis (New York, 1903). The work on bile acids was compiled in Die Säuren der Rindergalle and der Menschengalle (Hamburg, 1898). Einführung in die Chemie in letchifasslicher Form (Hamburg-Leipzig, 1899; 7th ed., Leipzig, 1927) was translated by M. M. Pattison Muir as An Introduction to Modern Scientific Chemistry (London, 1901).
II. Secondary Literature. There is a brief notice on Cohn by Friedrich klemm in Neue deutsche Biographie, III (Berlin, 1956), 316–317.
Albert B. Costa