Pictet, Raoul-Pierre

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(b. Geneva, Switzerland, 4 April 1846; d. Paris. France, 27 July 1929), low-temperature physics.

low temperature physics.

Pictet, son of Auguste Pictet-de Bock, a military officer in various foreign services, was descended from a prominent Geneva family. After studying physics and chemistry in Geneva and Paris (1868-1870), he returned to his native city and devoted himself to experimentation in the physics of low temperatures, with an eye to the fast-growing and lucrative refrigeration industry. A compression refrigeration system that he developed, with sulfur dioxide as its cooling medium, functioned at a much lower pressure than competing systems; contact with water, however, often turned the refrigerant into corrosive sulfurous acid. This system, protected by a number of patents, was marketed with some success.

It was Pictet’s researches that led to a scientific achievement which at once made him internationally famous. In December 1877, when Louis Paul Cailletet was about to report his liquefaction of oxygen to the Paris Academy of Sciences, Pictet cabled from Geneva that he had achieved the same feat. Cailletet and Pictet had worked independently and by different methods. While Cailletet’s method had been to compress, cool, and expand the gas to be liquefied, Pictet had employed the “cascade” process, in which the refrigeration cycles of three dilfcrent cooling media with successively lower critical temperatures were arranged in series, so that the gas liquefied first would act as a coolant in the liquefaction of the next. Pictet used sulfur dioxide in the first cycle, carbon dioxide in the second, and oxygen in the last. Although Cailletet could establish a priority of a few weeks. Pictet has been allowed to share the credit for the first liquefaction of an atmospheric gas. His claim also to have liquefied hydrogen was later shown to be based on error (Carl Linde, Aus meinein Lebentoutrou meiner Arbeit [Munich, n.d. (1916?)]. 68-72; Kurt Mendelssohn, The Quest for Absolute Zero [London, 1966], 41-42).

In 1879 Pictet was given a chair of“industrial physics” at the University of Geneva, which he held for seven years. In 1886 he left academic life to establish an industrial research laboratory in Berlin and to market his inventions. The chief feature of his refrigeraion system now became a patented refrigerant, Liquide Pictet (sulfur dioxide plus carbon dioxide), which involved him in controversy because he had claimed it to be exempt from the second law of thermodynamics. Although, asbefore, his machines were prone to disintegrate because of corrosion unless carefully shielded from moisture, he enjoyed some commercial success.During the later part of his life, spent in Paris, he continued to publish scientific papers; but his death in Paris, but his death in 1929 went virtually unnoticed.


I. Original Works. Pictet described his 1877 expeiment in Memoire sur la liquefaction de l’oxygene et la liquefaction et solidification de l’hydragene (Geneva, 1878). An extensive bibliography of his works is in Poggendorff, III, 1040; IV, 1163; V, 975; and VI, 2014.

II. Secondary Literature. Biographical data are found in an obituary by C. E.- Guye, in Comptes rendus des seances de la Société de physique et d’lilsiolre nature the de Geneve,, 47 (1930), 18-20; and in Dictionnaire historique et biographique de la Suisse, V (Neuchâtel, 1930). For discussions of his work see, besides Linde and Mendelssohn (cited in text), Ferdinand Rosenberger, Geschichte der Physik, III (Brunswick, 1887-1890), 416, 652-653; and W. R. Woolrich, The Men Who Created Cold (New York, 1967), 171-173.

Otto Mayr