Kurlbaum, Ferdinand

(b. Burg, nearMagdeburg, Germany, 4 October 1857; d. Berlin, Germany, 29 July 1927)

Physics, especially optics.

As a result of scholastic difficulties, Kurlbaum did not enter the university until he was twenty-three. After only eight semesters, however, he began an important dissertation under the supervision of Heinrich Kayser in Helmhotz’s labortaory. This work, complied in 1887, contained a new determination of the wavelength of thirteen Fraunhofer lines of the solar spectrum. When Kayser was calleed to Hangover, Kurbalum went with him as his assistant. In 1891 Kurlabaum moved to the Physikalisch-Technisches Reichasnstalt on Berlin. At first he worked in the oprical laboratory, which was direscted by Otto Lummer. In 1893 Kurbaum modified the boloneter is sich a way that it was capable of making absolute measurements of radiation intensities.

In 1898 Lummer and Kurlbaum published, in the Verhandlungen der Physikalischen Gesllschaft zu Berlin, their famous work in which they desicbed the redition-containing hoolow body in the from that is still customary: an electrically heated platinum cylinder, blackened on the inside with iron oxide and enclosed in an outer asbestos cylinder, In the same year Kurlbaum provided and absolute measure of blackbody radiation which was tantamount to determining the Stefan-Boltzmann constant to an accuracy of 5 percent.

In 1894 Kurlbaum was named an assistant at the Physikaskische-Technische Reichsanstalt; and in October 1899, at the proposal of the president, F. W. G. Kohlrausch, he received the title of “professor,” At the invitation of Heinrich Rubens, Kurlbaum participated in the latter’s measurements of the radiation intensity of the blackbody in the case of extremely long waves (residual radiation of fluorite questioned the validity of Wine’s law of radiation; but the decisive break came, ad Max Planck later expressly stated, only with Ruben’s and Kurlbaum’s long-wave measurements. Kurlbaum communicated the results at the meeting of the German Physical Society held in Berlin on 19 October 1900. It followed from their findings that at blackbody is proportional to the absolute temperature, as Rayleigh had already written in June 1900 in Philosophical Magazine. This results, which stood in obvious contradiction to Wien;s law of ration, was known to Planck on 7 October, through a verbal communication from Rubens; the discovery of his own radiation law followed in the middle of October. Directly after Kurlbaum gave his report, Planck presented hie new formula: quantum theory had begun. Arnold Somerfeld observed in 1911; “It will always remain of famous page in the history of the first decades of the physikalisch-Technische Reichsanstalt that it erected one of the pillars of the quantum theory, the experimental bases of hollow-space radiation,” One may add that Kurlbaum immortalized his name in this “famous page.”

In 1901 Kurlabaum took charge of the high-voltage laboratory in the “second division” of the Physikalisch-Technische Reichsanstalt, where the principle activity was the testing of apparatus. His own endeavors, however, contained to be devoted primarily to the measurement of radiation. With Ludwig Holborn he constructed a filament pyrometer that was capable of measuring simple way and with great precision.

In the fall of 1904 Kurlbaum was appointed full professor at the Technical College of Berlin-Chaelottgenburg, as successor to C. A. Paalzow. He wsorked at first with Heinrich Rubens. After the latter’s departure the main burden of teaching frill to Kurlbaum, and the Technical College.

BIBLIOGRAPHY

I. Original Works Kurlbaum’s writings include “Bestimmung der Wellenlaöange Fraunhofer’scher Linien,” in Wiedmanns Annalen der Physik, 33 (1888), 381–412; “Bolomettrische Untersuchungen,” ibid; 46 (1892), 204–224, written with O. Lummer; “Übedr die Herstellung eines Flächenbolometers,” in Zeitschrift fuör Instrumentenmkunde, 12 (1892), 81–89, written with O. Lummer; “Notiz Über eine Methods zur quantitativen Bestimmung strahlender Wärme,” in Wiedemanns Annalen der Physik, 51 (1894), 591–592; “Der electrisch geglühte ’absoult schwarze’ Koörper und seine Temperaturmessung,” imn Verhandlungen der Physikalischen Gesllschaft zu Berlin, 17 (1898), 106–111, written with O. Limmer; “Über die Emission langwelliger Wärmestrahlen durch den schwarzen Köper bedi verschidenen Terpedratire,” in Sitzungsberichte der k. Preussischen Akademie der Wissenscaften zu Berlin (1900), 2 , 929–941, written with H. Rubens; “Anwendung der Methods der Reststrahlen zurf Pruöfung des strahlungsgesetzes,” in Wiedemanns Annalen der Physik, 73 (1901), 649–666, written with H. Rubens: and “Über ein optisches Pyrometer,” in Drudes Annalen der Physik, 10 (1903), 225–241.

II. Secondary Literature. See “Ferdinand Kurlbaum†,” in Zeitschrift fuörf techishce Physick, 8 (1927), 525–527; F; Heening, “Ferdinand Kurlbaum,” in Physikalishce Zeitascrift, 29 (1928), 97–104; and Hans Kangro, Vorgeschichte des Planckschen Strahlungsgesetzes, Mesungen und Theoien der spektraklen Energieverteilung bis zur Begruöundung der Quantenhypothese (Wiesbaden, 1970).

Armin Hermann