Karl Friedrich Mohr

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Karl Friedrich Mohr

Karl Friedrich Mohr (November 4, 1806 – September 28, 1879) was a German chemist famous for his early statement of the principle of the conservation of energy. Ammonium iron(II) sulfate, (NH4)2Fe(SO4)2.6H2O, is named Mohr's salt after him.


Mohr was born in 1806 into the family of a prosperous druggist in Koblenz. The young Mohr received much of his early education at home, a great part of it in his father's laboratory. This experience may be responsible for much of the skill Mohr later showed in devising instruments and methods of chemical analysis. At the age of twenty-one he began to study chemistry under Leopold Gmelin, and, after five years in Heidelberg, Berlin and Bonn, he returned with the degree of PhD to join his father's establishment.[1]

Mohr's father died during 1840 at which time Mohr assumed control of the family business. He retired from it for a life of scientific leisure in 1857, but at the age of fifty-seven some serious financial losses caused him to become a privatdozent in Bonn. In 1867 he was appointed, by the direct influence of the government, extraordinary professor of pharmacy.[1]


Mohr burette

Mohr was the leading scientific chemist of his time in Germany, and the inventor of many improvements in analytical methodology. He invented an improved burette which had a tip at the bottom and a clamp (a 'Mohr's clip'), which made it much easier to use than its predecessors, which were more similar to a graduated cylinder. His methods of volumetric analysis were expounded in his Lehrbuch der chemisch-analytischen Titrir-methode (1855) (Instructional Book of Titration Methods in Analytical Chemistry), which won special commendation from Liebig and ran to many editions.[2] His Geschichte der Erde, eine Geologie auf neuer Grundlage (1866) (History of the Earth, a Geology on a New Basis), was also widely circulated.[3][1]

In a paper Über die Natur der Wärme (1837), Mohr gave one of the earliest general statements of the doctrine of the conservation of energy:[4]

besides the 54 known chemical elements there is in the physical world one agent only, and this is called Kraft (energy). It may appear, according to circumstances, as motion, chemical affinity, cohesion, electricity, light and magnetism; and from any one of these forms it can be transformed into any of the others. [1]

Selected writings[edit]

- Based on Mohr's work


  1. ^ a b c d Chisholm 1911.
  2. ^ Mohr, Karl Friedrich (1855). Lehrbuch der chemisch-analytischen Titrirmethode … , part 1 [Textbook of analytical chemistry titration methods …] (in German). Braunschweig, (Germany): Friederich Vieweg und Sohn.  Page 3 shows Mohr's burette.
  3. ^ Mohr, Friedrich (1866). Geschichte der Erde. Eine Geologie auf neuer Grundlage [History of the Earth, a Geology on a New Basis] (in German). Bonn, (Germany): Max Cohen & Sohn. 
  4. ^ Über die Natur der Wärme, Zeitschrift für Physik und verwandte Wissenschaften (Wien, 1937), Volume 5, pg 442. [1]

Further reading[edit]

 This article incorporates text from a publication now in the public domainChisholm, Hugh, ed. (1911). "Mohr, Karl Friedrich". Encyclopædia Britannica. 18 (11th ed.). Cambridge University Press. p. 650.