Hans Heinrich Landolt was a Swiss chemist known for discovering iodine clock reaction and founding the Landolt-Börnstein database. He also served as a professor at the University of Bonn, RWTH Aachen University and Humboldt University of Berlin.
Background
Hans Heinrich Landolt was born on December 5, 1831, in Zurich, Switzerland. His parents died when he was quite young, so he was brought up by his grandparents. They encouraged his early interest in science and allowed him to set up a small laboratory in the cellar; at thirteen Landolt was making fireworks.
Education
Landolt began his education in Zurich under Karl Löwig. He subsequently followed Löwig to Breslau, where he received his doctorate for work on arsenic ethyl. He then attended lectures by Rose and Mitscherlich in Berlin but found the laboratory facilities inadequate and soon moved to Heidelberg, where Bunsen’s laboratory had become a center for chemical studies. Here he investigated the luminosity of gases produced in a Bunsen burner and, on the strength of his work, became a privatdocent at Breslau.
Career
In 1857 Landolt became an associate professor at Bonn and in 1867 full professor. In 1869 he began to teach at Aachen, and in 1880 he moved to the Agricultural Institute in Berlin. He succeeded Rammelsberg in the Second Chemical Laboratory, Berlin, in 1891 remaining there until his retirement in 1905.
Primarily a physical chemist, Landolt centered his major work on molecular refractivity of organic compounds. In 1858 John Gladstone and Thomas Dale proposed an empirical formula which related the density and the refractive index of a substance. A second formula with a stronger theoretical basis was derived independently by H. A. Lorentz and Ludwig V. Lorenz in 1880. Berthelot, Gladstone, and Dale tried to correlate refractivity and chemical composition and suggested that molecular refractivity was an additive property. Landolt, studying fatty acids and esters, contributed to this view by arriving at values for the refraction of each element in a compound. In 1870 Gladstone showed that Landolt’s values yielded erroneous results with such unsaturated compounds as benzene and the terpenes. Further work by Landolt’s student Julius Wilhelm Bruhl showed that molecular refractivity was not strictly an additive property but was affected by constitutive factors as well. Landolt later extended his research on molecular refractivity, using rays of various wavelengths.
Landolt also investigated the velocity of the reaction between iodic and sulfuric acid. Because of his appointments at technical schools, he was also interested in the design and industrial applications of polarimeters. His main publication, written in collaboration with Richard Bornstein, is Physikalischchemische Tabellen. The book has been enlarged and reissued many times since Landolt’s death.
Landolt was a member of the Royal Prussian Academy of Sciences, the German Academy of Sciences Leopoldina, and the Saint Petersburg Academy of Sciences.
Royal Prussian Academy of Sciences
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Germany
German Academy of Sciences Leopoldina
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Germany
Saint Petersburg Academy of Sciences
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Russia
Personality
Landolt was known for his humor, friendliness, and punctuality.
Physical Characteristics:
Landolt was fit and worked as usual until the week before his death, when he had a sudden failure of heart and kidney.
Connections
In 1859, Landolt married Milla Schallenberg, the daughter of Swiss parents settled in Bonn.