Humboldt State University

Robert A. Paselk Scientific Instrument Museum

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Beckmann Differential Thermometer

Central Scientific Co.

Humboldt State College, <1940?

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The Beckmann thermometer was invented by Ernest Otto Beckmann (1853-1923), also noted for the Beckmann transformation in organic chemistry, as a result of his work with oximes. His interest in the physical properties of these molecules lead him to invent a number of ingenious apparatus for measuring colligative properties based on the theoretical work of Francois Marie Raoult (1830-1901). He began publishing this work around 1888. Beckmann developed the differential thermometer bearing his name, which could accurately measure temperatures to about 0.001° C, in order to measure the very small temperature changes found in boiling point and freezing point determinations of molecular weight.

Some early descriptions of the Beckmann thermometer and its use are provided below:


The thermometer is a Cenco model No. 19410 (made in Germany). It is 57.5 cm in overall length, with a 35.5 cm long milk glass baking inside the large tube. There is a nickel cap on top made of straight tubing to which a flat, knurled-edge top with a small turned knob in the center is soldered. The thermometer is graduated from -0.1 to 6.1 °C by 1/100 °C on the main scale, and from -9 to 144 °C by single degrees on the upper "setting" scale. The upper scale has every 10 degrees numbered (obviously by hand), while the main scale is numbered every 0.2° with larger numbering at each degree.

Research: The metal cap appears to be of an early style, not shown in the listings for 1976, 1960 (J-300, pg 257), 1950 (J-150, pg 367), or 1941 (J-141, pg 380) Cenco catalogs, even though the same model number is used (19410). A similar cap style does show up in the 1927 (C-227) Cenco catalog (p 664), but it is given a different catalog number (13522)


Gascoigne, Robert Mortimer. A Chronology of the History of Science, 1450-1900. Garland Publishing, Inc. New York (1987) pg. 137

Gienapp, Ruth Ann. "Beckmann, Ernest Otto" in Dictionary of Scientific Biography, vol. 1 (Charles Coulston Gillispie, editor), Charles Scribner's Sons. New York (1970) pg. 553.

Laidler, Keith J. The World of Physical Chemistry. Oxford Univ. Press. Oxford (1993) pg. 124.


HSC 1936-53 Scientific Instruments

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HSTC (1921-34)
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HSC (1935-1953)
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HSC (1954-1973)

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Last modified 30 August 2010