Svedberg, Theodor (1884-1971)

  Swedish chemist who won the Nobel Prize for Chemistry in 1926 for his studies in the chemistry of colloids and for his invention of the ultracentrifuge, an invaluable aid in those and subsequent studies.

  The Svedberg (b. Aug. 30, 1884, Fler䮧, near G䶬e, Sweden--d. Feb. 25, 1971, ֲebro) after receiving his doctorate from the University of Uppsala in 1907, Svedberg joined the faculty there. When he retired in 1949 he was named director of the new Gustaf Werners Institute for Nuclear Chemistry, a post he held until 1967.

  Svedberg's early research was on colloids, in which particles too small to be resolved by ordinary light microscopes are dispersed throughout water or some other substance. The particles in colloid solutions are so small that the jostling of the surrounding water molecules keeps them from settling out in accord with gravity. To better study the particles, Svedberg used centrifugal force to mimic the effects of gravity on them.

  Svedberg prepared a number of new organosols from more than 30 metals. Through an ultramicroscope, he studied the particles in these sols and confirmed Albert Einstein's theories about Brownian movement.
Svedberg discovered that thorium-X crystallizes with lead and barium salts (but not with others), anticipating English chemist Frederick Soddy's demonstration of the existence of isotopes.
Svedberg also investigated, about 1923, the chemistry involved in the formation of latent images in photographic emulsions.
Working on synthetic polymers, Svedberg introduced electron microscopy to study natural and regenerated cellulose, X-ray diffraction techniques to investigate cellulose fibres, and electron diffraction to analyse colloidal micelles and crystallites.

   In 1924 he constructed the first ultracentrifuge, a machine that allowed the rapid separation of particles by mass. This can reveal the presence of contaminants in a sample of a new protein, or distinguish between various long-chain polymers. His first ultracentrifuge, completed in 1924, was capable of generating a centrifugal force up to 5,000 times the force of gravity. Later versions generated hundreds of thousands of times the force of gravity. Svedberg found that the size and weight of the particles determined their rate of settling out, or sedimentation, and he used this fact to measure their size. With an ultracentrifuge, Svedberg went on to determine precisely the molecular weights of highly complex proteins such as hemoglobin. In later years he made studies in nuclear chemistry, contributed to the improvement of the cyclotron, and helped his student Arne Tiselius in the development of the use of electrophoresis to separate and analyze proteins.

   In the years immediately after the Second World War, several countries that were pushing to develop more powerful particle accelerators created an exclusive club. A recent symposium in Uppsala looked back to the first Swedish post-war accelerators.

  The first cyclotron in Sweden was a small 80 cm device built in 1938 at the Nobel Institute in Stockholm and capable of accelerating deuterons to 7 MeV. After the Second World War, an ambitious new machine at Uppsala took energies into a new domain.

  In the early 1940s, Helge Tyr鮬 former professor of high-energy physics, a student of 1926 Nobel Chemistry Laureate Theodor Svedberg, had constructed a neutron generator for the production of radionuclides. In Svedberg's discussions with the main customer of these radionuclides, gynaecology professor John Naeslund, plans emerged for a more powerful accelerator - a cyclotron - to increase the quantities of radioactive substances.

  Naeslund's wife knew G?org textile magnate Gustaf Werner, who was the richest person in Sweden at that time and known for his generosity. The firm Werner & Carlstr?ffered to finance a cyclotron, and one of its research objectives was to see how synthetic fibres were affected by neutron irradiation.