Award of the Duddell Medal of the Physical Society

Abstract

THE council of the Physical Society has awarded the tenth Duddell medal to Prof. Wolfgang Gaede, director of the Physical Institute at Karlsruhe, and until recently professor of physics at the Technische Hochschule there. Prof. Gaede's name will always be associated with the design and production of high vacuum pumps. Before 1905 the production of a vacuum beyond that attainable with a filter pump or piston pump was a tedious operation, carried out almost always with a mercury pump of the Toepler or Sprengel type. The remarkable thing about Gaede's investigations is not merely that at the age of twenty-seven he designed a rotary mercury pump which was simple, easy to work, and marked a great advance, but also that since then he has produced at intervals a number of vacuum pumps, each with a definite field of utility, and some of which are based on wholly new principles developed largely by Gaede himself. Thus the rotary mercury pump of 1905 (for many years the pump chiefly used in electric lamp manufacture) and the rotary oil pump of 1907 were followed in 1913 by the rotary box pump used as a backing pump for high vacuum pumps, and by the molecular air pump, which was the first of the really high-speed pumps. In 1915 came the mercury vapour diffusion pump, the forerunner of nearly all the highspeed vacuum pumps used to-day, whether employing oil or mercury vapour. Within the last ten years, Gaede has designed a family of pumps of several stages, incorporating both the high-vacuum and the fore-vacuum pump into a single unit. A recent outstanding development was the large single-stage diffusion pump designed by Gaede for work at Leyden on solid helium. This had the remarkable speed of several hundred litres per second at a pressure of 1/1000 mm. mercury.