Hans Heinrich Landolt

Hans Heinrich Landolt (5 December 1831 – 15 March 1910) was a Swiss chemist who discovered iodine clock reaction. He is also one of the founders of Landolt–Börnstein database. He tested law of mass conservation which was given by Lavoisier.

Biography Landolt was born in Zurich and at the age of nineteen entered the university there to study chemistry and physics. He attended the lectures of Carl Jacob Löwig and published his first work on stibmethyl in Schriften der Naturforschenden Gesellschaft (Writings of the Natural Science Society). He was then appointed assistant to Lowig and followed him in 1853 to Breslau. The same year he obtained the degree of Doctor of Philosophy with a thesis "Ueber die Arsenäthyle" (On ethyl compounds of arsenic) which was a notable contribution to the law of chemical valence. After the defense, he went to Berlin to attend lectures of Eilhard Mitscherlich, Rose, Johannes Muller and Dubois. Facilities for experimental research in chemistry were practically non-existent in Berlin at the time, and therefore Landolt left for Heidelberg for a newly founded institute of Robert Bunsen. After devoting himself for a short time to the electrolytic production of calcium and lithium, Landolt started an investigation of the gases produced in the Bunsen burner, which had been constructed in the winter of 1854–55. From 1891 till his retirement in 1905, he served as director of the second chemical institute of the Berlin University. There he worked on three major problems: (i) relation between the melting point and molecular weight, (ii) effect of crystallinity on the optical rotation and (iii) change in weight during chemical reactions. The negative result for the last experiments was regarded as an accurate experimental confirmation of the conservation laws of mass and energy.

Landolt was known for his humor, friendliness, punctuality and cigar. He was fit and worked as usual until the week before his death, when he had a sudden failure of heart and kidney. He was buried, in accordance with his desire, at Bonn where he spent most memorable years of his life.