Mohr, Carl Friedrich

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(b. Koblenz, then France [now Germany], 4 November 1806; d. Bonn, Germany, 28 September 1879)

analytical chemistry, physical chemistry, agricultural chemistry, geology.

Mohr’s father, Karl, was an apothecary and city councillor. After completing secondary school, Mohr attended the University of Bonn, where he studied botany, chemistry, and mineralogy. After gaining practical experience with his father, he attended the chemistry lectures of Leopold Gmelin at Heidelberg and those of Heinrich Rose in analytical chemistry at Berlin. He then obtained his degree in pharmacy and took over his father’s business. Besides attending to the business, he was interested in various areas of science. In 1833 he married Jacobine Derichs; they had three sons and two daughters.

In 1837 Mohr published an essay, “Ansichten über die Natur der Wärme,”in which he wrote:“Apart from the known chemical elements, there exists in nature only one agent, and that is force; it can show itself in appropriate relationships as motion, chemical affinity, cohesion, electricity, light, heat or magnetism. And out of each of these kinds of phenomena all the others can be produced” (Zeitschrift für Physik, Mathematik und verwandte Wissenschaften, 5 [1837], 419). On the basis of this statement, he later claimed priority regarding the law of the conservation of energy. In 1847 Mohr wrote a commentary on the Prussian pharmacopoeia and Lehrbuch der pharmazeutischen Technik. In this period he also carried out titrimetric experiments, the results of which are in Lehrbuch der chemisch-analytischen Titriermethode (1855). In the meantime Mohr had established a vinegar factory with his son-in-law and purchased an estate at Metternich, to which he moved after selling his apothecary’s shop. He now concerned himself with fermentation and the cultivation of grapes, and wrote popular books on these subjects. He also experimented with artificial fertilizers, following the ideas of his close friend Liebig. In 1863 his factory failed, and Mohr found himself and his family in financial difficulties. Through Liebig’s help he qualified as a Privatdozent at the University of Berlin, at the age of fifty-nine. A short time later he moved to Bonn and was Dozent at the university there. He soon turned to new areas of research and studied geology, on which science he developed original but wholly incorrect opinions.

Mohr’s attention next turned to thermodynamics. He recalled his statement on force and had it reprinted in a book. His commentary on it is chracteristic: “This passage was written by me thirty-three years ago and contains, as I now see, the main features of the mechanical theory of heat.” Mohr published several works in this field; but because he lacked the necessary mathematical knowledge, his works were failures.

Mohr had a passionate, critical, and combative nature and was therefore unpopular with his colleagues. He was active in many areas, yet much of his activity was marked by dilettantism. He was a skillful author and wrote many books.

Mohr’s most lasting contribution was in titration. His Lehrbuch … Titriermethode was the first successful compendium in this new field of analytical chemistry; It went through eight new editions between 1856 and 1913 and was translated into several languages. Mohr invented many new titration procedures and examined and often improved most of the older ones. Many methods and designs of apparatus bear his name: the Mohr test for iron and chloride determination, the Mohr pinchcock burette, the Mohr balance for the determination of specific gravity, and Mohr’s salt (ferrous ammonium sulfate) are evidence of his skill in the laboratory. The cooling device generally called the Liebig reflux and the useful cork borer were also invented by Mohr.


I. Original Works. Mohr’s writings include Commentar zur preussischen Pharmacopöe, 2 vols. (Brunswick, 1847; 2nd ed., 1853); Lehrbuch der pharmazeutischen Technik (Brunswick, 1847; 2nd ed., 1853), also trans, into English as Practical Pharmacy (London, 1848) and as Practice of Pharmacy (Philadelphia, 1849); Taschenbuch der chemischen Receptirkunst (Hamburg, 1854); Lehrbuch der chemisch-analytischen Titriermethode (Brunswick, 1855; 6th and 7th eds., with A. Classen, 1880 and 1896; 8th ed., with H. Beckurts, 1912), trans, into French as Traité d’ana lyse chimique par la méthode des liqueurs titrées (Paris, 1888); Der Weinstock and der Wein (Koblenz, 1864); Geschichte der Erde (Bonn, 1866); Mechanische Theorie der chemischen Affinität und die neuere Chemie (Brunswick, 1868); and Allgemeine Theorie der Bewegung und der Kraft als Grundlage der Physik und Chemie (Brunswick, 1874). Many of his articles appeared in Poggendorff’s Annalen der Physik and Justus Liebigs Annalen der Chemie.

II. Secondary Literature. See E. E. Aynsley and W. A. Campbell, “Karl Friedrich Mohr’s Contributions to Chemical Apparatus,” in School Science Review (1959), 312; R. Hasenclever, “Erinnerungen an Friedrich Mohr,” in Berichte der Deutschen chemischen Gesellschaft, 33 (1900), 3827; G. Kahlbaum, Justus von Liebig und Friedrich Mohr in ihren Briefen (Leipzig, 1904); Ralph E. Oesper, “Karl Friedrich Mohr,” in Journal of Chemical Education, 4 (1927), 1357; J. R. Partington, History of Chemistry, IV (London, 1964), 317–318; J. M. Scott, “Karl Friedrich Mohr, Father of Volumetric Analysis,” in Chymia, 3 (1950), 191; and F. Szabadváry, History of Analytical Chemistry (Oxford-New York, 1966), pp. 241–250, also available in German, Geschichte der analytischen Chemie (Brunswick, 1966), pp. 245–257.

F. SzabadvÁry