Siedentopf, Henry Friedrich Wilhelm

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(b. Bremen, Germany, 22 September 1872; d. Jena, Germany, 8 May 1940)


Siedentopf was a distinguished practitioner of scientific microscopy and a pioneer in ultramicorscopy and microphotography. After graduating from the Gymnasium in Bremen, he studied at Leipzig and Göttingen and became assistant to the mineralogist and crystallographer Theodor Liebisch. In 1896 Siedentopf received the doctorate at Göttingen under Woldemar Voigt for the dissertation “Über die Capillaritätsconstanten geschmolzener Metalle.” He became assistant to Franz Richarz at reifswald in 1898 but the following year accepted an offer from Ernst Abbe to join the Zeiss optical works in Jena. Siedentopf first worked in Abbe’s laboratory, and from 1907 to 1938 he was director of the company’s microscopy division. In 1918 he was named both titular and ordinary professor at the University of the Jena, where he lectured on scientific microscopy. With Hermann Ambronn and August Köhler he gave courses at Jena every summer.

Siedentopf’s most important achievement was the development of the “slit ultramicroscope,” which he perfected in 1902–1903 in collaboration with Richard Zsigmondy. They constructed the instrument in order to make visible the gold particulars in ruby glass, which Zsigmondy had unsuccessfully attempted to do alone. The device was based on the principle that under intense illumination with an electric arc lamp, the ultramicroscopic particles can be made to act as origins of small diffraction cones, which are visible in the objective. In the instrument ht e smallest particles were no longer illuminated from below, as in the ordinary microscope, but from the side; and the light they that refracted appeared in the ultramicroscope’s of view. Zsigmondy later developed this instrument into the immersion microscope, and Siedentopf created the cardioid ultramicroscope. From 1907 and 1923 he constructed skin and capillary microscopes, and in 1922 he developed the photomicroscope with “phoku” eyepiece and attached miniature camera. The latter device was a milestone in the development of microphotography.


Original Works. Siedentopf wrote about 50 scientific papers and obtained a number of patents for optical and microscopical devices, See Poggendorff, IV, 1394: V, 1162; VI, 2442; VIIa, 4, 405. His works include “über die Sichtbarmachung und GrÖssenbestimmung ultramikroskopischer Teilchen mit besonderer Anwendung von Goldrubinglösern,” in Annalen der Physik 4th ser., 10 (1903), 1–39, written with R. Zsigmondy: BisphÖrische Spiegelkondensatoren für Ultramikroskopie,” ibid., 39 (1912), 1177–1186: Ubungenzur wissen chaftlichen Microskopie (Leipzig, 1913); “Ultramikronen,” in Kolloid Zeitschrift, supp. to 36 (1925), “Zsigmondy-Festschrift,” 1–14; “Uber die optische Abbidung von Nicht-Selbstleuchtern,” in Zeitschrift für Physik50 (1928), 297–309: and “Microskopische Beobachtungen an Strichgittern mit periodischen Teilungsfehlern,” ibid., 107 (1937), 251–257: 108 (1938), 279–287: 109 (1938), 260–272: and (with similar title) 112 (1939), 704–726.

II.Secondary Literature. Obituary nbotices are in Deutsche optische Wochenschrift61 (1940), 110: and Kolloid-Zeitschrift, 91 (1940), B218: a biography is being prepared by F. Stier for Neue deutsche Biographie, See also the following, listed chronologically: F. Hauser, “Die Entwicklung mikroskopischer Apparate bei der Firma Zeiss in dem ersten Jahrhundert ihres Beste hens,” in Jenaer Jahrbuch (1952), no 4. supp., “Carl Zeiss 150. Geburtstag,” 25: and H. Gause, “Das Spaltultramikroskop nach Siedentopf und Zsigmondy—eine historische und optische Betrachtung,” ibid., no 6, 327–333.

Hans-GÜnther Korber