A German-made Beckmann thermometer (c.1940) in the collection of the Robert A. Paselk Scientific Instrument Museum at Humboldt State University. It is 57.5 centimeters in overall length, and 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.
A Beckmann thermometer, also known as a Beckmann differential thermometer, is a mercury-in-glass thermometer used in calorimetry which offers an accuracy of up to ±0.001K but which has a range of only 5K. This is achieved through its having a large bulb and fine bore. It was devised by the German organic chemist Ernst Otto Beckmann (1853–1923), who is also remembered for his discovery (1886) of the Beckmann rearrangement of ketoximes (see oximes) into amides under acid catalysis.