Landolt, Hans Heinrich

(b. Zurich, Switzerland, 5 December 1831; d. Berlin, Germany, 15 March 1910)

chemistry.

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, 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. A year later, in 1857, Landolt became 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. He was elected to the Berlin Academy in 1882.

Primarily a physical chemist, Landolt centered his major work on molecular refractivity of organic compounds (specific refraction × molecular weight). 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 shoed that Landolt’s values yielded erroneous results with such unsaturated compounds as benzene and the terpenes. Further work by Landolt’s student Julius Wilhelm Buühl 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 spolarimeters. His main publication, written in collaboration with Richard Börnstein, is Physikalisch-chemische Tabellen (1883). The book has been enlarged and reissued many times since Landolt’s death.

BIBLIOGRAPHY

I. Original Works. Landolt wrote over forty articles, including “Ueber die Zeitdauer der Reaction zwischen Jodsàure und schwefliger Sàure,” in Sitzungsberichte der Preussischen Akademie der Wissenschaften zu Berlin (1885), pt. 1, 249–284; (1886), pt. 1, 193–219; pt. 2, 1007–1015; (1887), pt. 1, 21–37; and “Ueber den Einfluss der atomistischen Zusammensetzung C, H, and O-haltiger flüssiger Verbindingen auf die Fortpflanzung des Lichts,” in Annalen der Physik und Chemie, 122 (1864), 545–563; 123 (1864), 595–628. With Richard Börnstein he wrote Physikalischchemische Tabellen (Berlin, 1883).

II. Secondary Literature. Works on Landolt include the following, listed chronologically: J. H. van’t Hoff, “Gedächtniss Rede auf Hans Heinrich Landolt,” in Abhandlungen der K. Preussischen Akademie der Wissenschaften zu Berlin, phys.-math. Kl. (1910), 67, English adaptation in Journal of the Chemical Society of London; 99 (1911), 1653; Richard Pribam, “Nekrolog auf H. Landolt,” in Berichte der Deutschen chemischen Gesellchaft, 44 (1911), 3337; and A. Idhe, Development of Modern Chemistry (New York, 1964), pp. 265, 393.

Ruth Gienapp Rinaerd