Karl Ferdinand Herzfeld (February 24, 1892 – June 3, 1978) was an Austrian-American physicist. Education Herzfeld was born in Vienna during the reign of the Habsburgs over the Austro-Hungarian Empire. "He came from a prominent, recently assimilated Jewish family." His father was a physician and ordinarius professor of obstetrics and gynecology at the University of Vienna. His mother, Camilla née Herzog, was the daughter of a newspaper publisher and sister of the organic chemist R. O. Herzog. In 1902, when Herzfeld was 10 years old, he was enrolled in the private Gymnasium Schottengymnasium, which was run by the Benedictine Order of the Roman Catholic Church and had its name derived from the fact that the founders came from Scotland. He attended this school until 1910, when he began attending the University of Vienna to study physics and chemistry. In 1912, he took courses at the University of Zurich and the Eidgenössische Technische Hochschule Zürich (ETH). It was in Zurich he met Otto Stern, who was at the ETH; Herzfeld later credited conversations with Stern for his deeper understanding of thermodynamics. In 1913, he went to study at the University of Göttingen, after which Herzfeld returned to Vienna, and was granted his doctorate in 1914, under Friedrich Hasenöhrl, who had become Director of the Institute for Theoretical Physics, upon the suicide of Ludwig Boltzmann in 1906. Herzfeld's doctoral thesis applied statistical mechanics to a gas of free electrons as a model for a theory of metals. By the time he received his doctorate, he already had published six scientific papers. In one of them, he attempted to derive a model of the hydrogen atom. This paper was published in 1912, shortly before Niels Bohr submitted his first paper on the Bohr model of the hydrogen atom. Upon receipt of his doctorate, Herzfeld volunteered for service in the Austro-Hungarian Army. World War I broke out shortly thereafter and he served until 1918, rising to the rank of first lieutenant. Herzfeld's thesis advisor Hasenöhrl was called to serve during World War I and was killed at the front. During his tenure in the military, Herzfeld published six papers on statistical mechanics applied to problems in physics and chemistry, especially to the structure of matter – gases, liquids, and solids. After the War, Herzfeld returned to the University of Vienna, however, the University was in such dire financial straits that he moved to Munich