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Paul Karl Moritz Knipping

In the year 2012, crystallographers will celebrate the centenary of the first successful experiment of diffraction of X-rays (Röntgenstrahlen) by crystals. Max von Laue had been awarded the Nobel prize in 1914 for his genius idea to prove both the wave nature of X-rays and the periodic arrangement of atoms in crystals. This experiment was carried out in the physics laboratory of the University Munich and has had a tremendous influence on many disciplines of science in the last 100 years. Crystal structures ranging from NaCl (Bragg and Bragg, 1913) to biological macromolecules have been determined. Whereas Max von Laue (then private lecturer at Munich university) as a theoretician proposed the experiments he had to rely on two PhD-students to do the work in reality. He convinced Paul Knipping and Walter Friedrich (a PhD-student with the professor of theoretical physics, Sommerfeld) to carry out the experiments which had to be performed in addition to their actual thesis work. They used an X-ray tube and tried several crystals which were at hand. The photographic plates which should register the scattered light were initially arranged parallel to the beam. For weeks no success was achieved. The legend says that Knipping who was sitting in the same room writing his thesis, annoyed by some noise, changed the arrangement and placed the plates behind the crystal. Thus, finally, interference reflections were detected from copper sulphate (CuSO2 5H2O) in transmission mode (now the Laue geometry). The great idea of Laue has been rewarded many times and will definitely be honoured again next year. Walter Friedrich (died 1968) was a famous professor in Berlin, member of the Akademie der Wissenschaften (Academy of Sciences) in Berlin (East) and even some streets have been named after him. Little is, however, known about Paul Knipping. As Knipping was a professor at Technische Hochschule Darmstadt and in a sense my pre-predecessor, I present here those details which I found in the archives of our University (1). Paul Karl Moritz Knipping was born on 21 May 1883 at Neuwied, a small town in the Rhine-valley close to Koblenz. His father Paul was a medical doctor (Sanitätsrat), his mother was Emilie Hatzfeld. Knipping married Dr. Phil. Thea Krüger in 1918. She was the daughter of the General Georg Krüger and was a medical doctor, exceptional for a woman in those days. He died on 26 August 1935 in Darmstadt in a road accident riding his motorcycle. His wife and a son survived him (2). Paul Knipping started his University studies at Heidelberg in 1904. After 1 year he changed to Munich to continue and finally concluded with a PhD thesis (Dr. Phil.) with the title ‘Über den Einfluss der Vorgeschichte auf verschiedene Eigenschaften des Bleies’ (Bayrische Staatsbibliothek München). Translation: ‘About the influence of the pretreatment on various properties of lead’ (3). During the period 1913–1922, he occupied several positions as scientific assistant. Some sources speak about a position at the Kaiser-Wilhelm-Institut für Physikalische Chemie in Berlin, others about the Universities in Berlin and Heidelberg. His experimental work concerned ionization of molecules by electron bombardment, but it is said that many drawbacks and opposite winds (widrige Schicksale und bittere Enttäuschungen) marked that period.