University ® Department
Beckmann Differential Thermometer
Brooklin Thermometer Co.
(web) & ISI (display case)
Humboldt State College, c. 1960-70
- 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 Today it is superceded by sensitive digital thermometers using thermocouples, thermistors, etc.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:
- 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.
- 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.
- © R. Paselk
- Last modified 13 August 2010