Humboldt State University ® Department of Chemistry

Robert A. Paselk Scientific Instrument Museum

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Beckmann Differential Thermometer

Brooklin Thermometer Co. (web) & ISI (display case)
Humboldt State College, c. 1960-70

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Use/History

The Beckmann differential thermometer is used for measuring small differences in temperature, having a readability of around 0.001°C. This makes it useful for the determination of melting points, boiling points and calorimetry. Today it is superceded by sensitive digital thermometers using thermocouples, thermistors, etc. as probes. The chemistry department at HSC had at least six of these thermometers in the 1980's, an early Cenco Beckmann thermometer , two Brooklyn Beckmann thermometers, a couple of ISI Beckmann thermometers and one with a standard taper ground joint.
 
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:

Description

The thermometer illustrated is made in Germany for the Brooklyn Thermometer Company, model, it is two large to fit the display case, so a shorter, ISI thermomtter is displayed. The Brooklyn thermometer is 64 cm (25") 0000in overall length, with a 32 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. The thermometer is graduated from -0.24 to 5.55°C and -0.25-5.54°C by 1/100 °C on the main scale , and from -10 to 150 °C by two degrees on the upper "setting" scale (photo image of setting scale). The upper scale has every 20 degrees numbered, while the main scale is numbered every 0.2° with larger numbering at each degree (photo image of scale graduations).

A certificate accompanied this thermometer which may be viewed as a scan of the certificate and a scan of the envelope contaning it.

References

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.

From the Analytical/Physical Chemistry Lab - Exhibit Catalog

 HSTC icon
HSTC (1921-34)
HSC 54-73 icon
HSC (1954-1973)
HSC 35-53 icon
HSC (1935-1953)

HSC 1956-72 Instrument Collection

© R. Paselk
Last modified 13 August 2010