He is known for inventing the Beckmann thermometer. Enter Ernst Otto Beckmann (1853-1923) was born in Solingen, the German town famed for its knives. The son of a dye-maker, he grew up with chemistry in his blood. He studied with the great analyst Fresenius at Wiesbaden and then with Hermann Kolbe in Leipzig. While working on oximes derived from ketones he discovered a curious reaction – in the presence of Lewis acids, they could rearrange to amides: a useful method of turning cyclic ketones into ring-expanded lactams. This reaction came to bear his name, the Beckmann rearrangement.
Yet the chemistry
was so complex, Beckmann was led to suspect that he might be isolating polymers. Raoult’s work on vapour pressures seemed to provide a means of determining the molecular weights. To do this, Beckmann developed an ingenious differential thermometer of exquisite precision. This is an unusually precise mercury-in-glass thermometer that was designed to measure temperatures over a very small range, especially near the melting and freezing points of substances. The thermometer typically covers a small range of 5 °C, but it is possible to estimate temperature changes with an accuracy of 0.001 degrees. This example has a long cylindrical bulb at the bottom, an S- shaped tube with auxiliary bulb at the top, and a porcelain plate carrying a scale that ranges from -0.4 to +1.1 degrees Centigrade and that is graduated to 0.002 degrees. The back of the plate is marked “Centigrade” and “Thermometer n. Beckmann.” The whole is enclosed in a cylindrical glass tube with brass cap.The ability to measure such tiny temperature differences made it possible to investigate systems unthinkable previously.
