Heinrich Geissler was a German glassblower and physicist. He was a mechanic at the University of Bonn.
Background
Heinrich Geissler was born on May 26, 1814, in Igelshieb, Germany. His father, Johann Georg Jacob Geissler, was a maker of glass beads and a burgomaster. His mother, Johanne Rosine Eichhorn, was the daughter of a glassmaker. He was descended from other craftsmen active in the Thüringer Wald and in Böhmen, and two of his brothers worked as mechanicians, one in Berlin and the other in Amsterdam.
Education
Geissler learned glassblowing in the duchy of Saxe-Meiningen. He was awarded an honorary doctorate by the University of Bonn in 1868.
Career
Johann began working while very young. He is said to have worked in the Netherlands for some eight years. In 1841 he founded his workshop in Bonn. Geissler finally settled as a mechanic at the University of Bonn in 1852 and established a workshop for producing chemical and physical instruments. He provided many instruments for the mechanician W. H. Theodor Meyer and the physicist Julius Plücker, as well as for the mineralogist H. P. J. Vogelsang and the physiologist Eduard Pflüger. Later he was associated with Franz Müller, who succeeded him as an owner of the workshop.
Talented both in making instruments and in comprehending their physical bases, Geissler learned much from his association with the scientists at the university. He became an indispensable participant in the experimental work that was being conducted there.
The first account of Geissler’s activity dates from 1852, when, with Julius Plücker, at Bonn, he constructed his famous structed thermometers. They differed from the thermometers then in use by their thin glass, by the application of capillarity, and by their high precision. For calibrating he used his new glass balance that had a sensitivity of 0.1 mg. of mercury. In 1863 Geissler constructed a maximum thermometer based on Casella’s minimum thermometers. Also in 1852 Geissler, at the invitation of a Bonn industrialist, constructed an instrument for measuring the alcoholic strength of wine. This “vaporimeter” measured the pressure of vapors of alcohol and air against mercury. Plücker improved the apparatus by eliminating the air and was thus stimulated to investigate vapors scientifically. Geissler also used the instrument to measure the strength of liquid ammonia.
There is a second invention connected with Geissler’s tubes. The difficulty in obtaining a vacuum with the piston pumps then in use caused Geissler to construct a mercury air pump about 1855. Demonstrated to a wider public in 1858, it was an improvement on the idea of using Torricelli’s vacuum for evacuation, which the theosopher Emanuel Swedenborg had described in 1722 and many others after him had tried to use. Geissler’s pump, entirely of glass and thick rubber, was operated by manually moving a second tube up and down and therefore was slow, though effective.
Through the use of this pump and his aptitude for glassblowing, Geissler was able to make rather small glass tubes with electrodes melted into the ends and filled with rarefied gases. By using these tubes Plücker was able to study discharges in very rarefied gases. The new and most interesting phenomenon, the stripes in the discharge light, previously observed in the “electrical egg” by Rühmkorff and Jean Quet, could now, by means of “Geissler’s tubes,” be studied in detail. These tubes provided a much better vacuum and, in contrast with the “electrical egg,” were not dependent on a pump. At the thirty-ninth meeting of the Deutsche Naturforscher und Ärzte, held at Giessen in 1864, Geissler demonstrated his mercury pump. “Geissler’s tubes” were shown there in experiments by J. C. Poggendorff to demonstrate induced currents. On the whole, the technology of “Geissler’s tubes” helped to introduce a new branch of physics which led directly to the discovery of the cathode rays.
In addition, the thermometer tubes enabled Geissler to construct in 1852 an instrument for measuring the expansion of freezing water and ice. In 1858 Geissler suggested to Justus von Liebig that the chemical nature of gases could be identified by means of the discharge in “Geissler’s tubes.” This was further implemented by Vogelsang and Geissler in 1868, when they described a vacuum tube in which liquids occluded in minerals could be identified chemically by means of the then-new technique of spectral analysis. About 1860, in the inner of these tubes, Geissler converted white phosphorus into the red form “by electricity,” as he put it. In 1873 he demonstrated the phenomenon before Anton von Schrötter at the world exhibition in Vienna.