Karl Weissenberg - The 80th Birthday Celebration Essays
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Dr. Karl Weissenberg: 1922-28

 

 

PROFESSOR A. MARK

Polytechnic Institute, Brooklyn, U.S.A.

 

 

When I came to the Kaiser Wilhelm Institute fuer Faserstoffchemie in 1922 Dr. Weissenberg had just joined a group of scientists who started to investigate systematically the molecular structure of natural fibres.

 

Already in 1913 Nishikawa and Ono had obtained a faint x-ray pattern from cellulosic fibres and in 1918 Scherrer confirmed this finding, but these isolated observations wei e not followed up by a sustained research effort. R. O. Herzog, however, in 1913 assembled a team of young research associates and directed them to embark on a broad basis on the x-ray investigation of a variety of natural fibres under a variety of conditions. The first result, obtained by W. Jancke, were reproducible x-ray patterns of cellulosic fibres, particularly Ramie which indicated the presence of some crystallinic compound in these materials.

 

The next necessary step would evidently be the interpretation of these diagrams and their significance for the chemical structure of cellulose. It was started by M. Polanyi who, in 1921, concluded that the x-ray patterns, as such, offered as alternatives the existence of a long chain or of a four-membered ring, each built up of glucopyranose units. Herzog and Polanyi realized that the new type of diagram - the so-called fibre diagram - was of interest and importance not only for cellulosic fibres but for many other oriented filiform materials such as silk, wool and tendon and also for metallic wires and ceramix threads.

 

Polanyi organized and directed this broad research effort which demanded experimentalists for the preparation of the various samples for the taking of the x-ray diagrams and for mechanical, thermal and chemical measurements with the investigated products.

 

As time went on his group included R. Brill, E. Gomperz, E. Schmidand and myself. We were all more or less familiar with chemistry and physics but it was evident that substantial progress in the field would need considerable knowledge and versatility in mathematics and crystallography. This is where Karl Weissenberg completed the competence of Polanyi’s research team. Frequently Brill and I would look at one of our fibre diagrams and admire its regularity and consider it useful for a wallpaper or for other decorative purposes. Weissenberg would immediately get absorbed in its quantitative interpretation and after a few minutes of operation with the slide rule, come back with a number of figures which indicated numerically the meaning and significance of the experiment. He was our guardian angel and our instructor in mathematics and particularly in crystallography. In fact, for several months Weissenberg held a special Seminar on crystallographic principles in which he interpreted to all of us the books of Schoenfliess and Niggli and initiated for organic compounds a development similar to that which V. M. Goldschmidt had worked out at the same time for inorganic crystals. The clarification which he brought to all of us stimulated the x-ray study of many simple organic compounds with the result that the x-ray laboratory in Berlin-Dahlam started to rival successfully with the world famous Royal Institution in London, where organic molecules were systematically studied by Sir William Bragg with a team of younger scientists. Another important research activity of Weissenberg had to do with the orientation of microcrystalline metals under the influence of mechanical deformation, a research project which had been started by Polanyi and Schmid was expanded and successfully pursued by Weissenberg. But all this was only secondary to the two great achievements in the period from 1922 to 1928.

 

One of them was the idea and the complete design of an x-ray goniometer, which permits a three-dimensional resolution of the individual diffraction points and eliminates all ambiguities in the indexing of the diagrams. This Weissenberg Goniometer exists meanwhile in many different modifications, is in worldwide use and is an apparatus without which no complicated maoromolecular system would have been elucidated. In particular all modern and advanced structure proposals for proteins, nucleic acids and enzymes owe their existence entirely to the systematic use of the Weissenberg Goniometer. In chemistry and biology it is of the same importance as the ultracentrifuge or the electron microscope. Whereas the Weissenberg Goniometer represents an enormous step forward in the instrumentation of experimental x-ray analysis, Weissenberg also made a similarly important theoretical introduction in the systematic procedure to correlate the purely geometrical results emerging from a crystallographic x-ray study of organic substances with the symmetry, size and structure of the individual molecules which form the lattice. This systematization of molecular lattices in respect of the significance of the symmetry elements for the character of the lattice building units was originally conceived by A. Reis but was put on a general and all encompassing basis by Weissenberg; it makes it possible to translate the symmetry characteristics of the unit cell directly and immediately into statements which refer to the molecular structure of the investigated substance.

 

Even though these two great and independent contributions of Weissenberg represent already an unusually significant scientific achievement, they were by no means all what he did while he worked at the Kaiser Wilhelm Institute in Dahlem. Our whole group was permanently and increasingly influenced by his presence. If one brought a problem to him he was able and willing to cut it down to its bone, analyze its elements and formulate a general and systematic approach for its solution. Weissenberg combines his eminently mathematical and fundamental way of thinking with an unusually deep understanding for the complexity and for the intricate behaviour of matter. His contributions to rheology are a proof of this great gift but his work on crystal lattices already gave an indication of it.

 

Socially Karl Weissenberg was a delightful companion and an ever helpful friend, full of stories and jokes, an excellent tennis player and for all of us an unforgettable figure of our Dahlem days. I am sure I speak in the name of the entire group if I extend to him our best and most cordial congratulations on his 80th birthday and our best wishes for many more peaceful and happy years.

 

 


Contents

Preface  /  Acknowledgements  /  Biographical Notes

Weissenberg’s Influence on Crystallography

Karl Weissenberg and the Development of X-Ray Crystallography

The Isolation of, and the Initial Measurements of the Weissenberg Effect

        The Role of Similitude in Continuum Mechanics

The Effect of Molecular Weight and Concentration of Polymers in Solutions on the Normal Stress Coefficient

        Elasticity in Incompressible Liquids

The Physical Meaning of Weissenberg's Hypothesis with Regard to the Second Normal-Stress Difference

        A Study of Weissenberg's Holistic Approach to Biorheology

The Weissenberg Rheogoniometer Adapted for Biorheological Studies

        Dr. Karl Weissenberg, 1922-28

Weissenberg’s Contributions to Rheology

The Early Development of the Rheogoniometer

        Some of Weissenberg's More Important Contributions to Rheology: An Appreciation

        Publications of Karl Weissenberg and Collaborators  /  List of Contributors

Index

 

 

© Copyright John Harris