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Ewald Jurgens (George) von Kleist, German administrator and cleric, who discovered in 1745 the Leyden jar, a fundamental electric circuit element for storing electricity, now usually referred to as a capacitor. The device was independently discovered at about the same time by Pieter van Musschenbroek, who investigated it more thoroughly than Kleist. Ewald Jurgens (George) von Kleist (born in Prussian Pomerania, c. 1700) was the son of a Prussian district magistrate.
He studied at the University of Leyden in the 1720’s. While a student there he may have encountered the demonstrations in experimental physics of Professor Gravesande who was involved in electricity at Leyden. He apparently acquired his interest in science while at the University of Leyden. Kleist returned to Pomerania to become dean or bishop of a cathedral chapter of Camin in Pomerania (now Germany). Von Kleist was a member of Prussian administrative squirearchy (or gentry), but was said to be seeking the ignition of spirits by sparks when involved with electricity.
Germans were interested in electricity, and the interest was spreading to Berlin in the 1740’s. At this period of time men interested in science were full of excitement stirred up by G.M. Bose, then a professor of the University of Leipzig, Germany. Individuals engaged with the phenomenon of electricity were igniting combustibles by using sparks from electrical friction machines. Frederick the Great had just opened the Berlin Academy of Sciences in January 1744. The newly opened Academy was holding demonstrations and experiments in electricity. Demonstrators ignited alcohol, gun powder, and turpentine by electrical sparks, and people upon hearing about these events went to hear and see for themselves.
Since electricity from frictional sources was usually weak, electricians of the eighteenth century searched for ways to increase charge and to accumulate as much of it as possible on a substance. If charge could be accumulated the electricians could then broaden their research with the mystical phenomenon. The discovery of a device that was able to conserve quantities of charge for later use occurred in November 1745 and January 1746. Independently, two men discovered that electricity produced by an electrical friction machine could be accumulated and stored. Both men were horrified and surprised when their newly created device discharged into their bodies.
Von Kleist apparently was also stimulated by Bose, and so made his own electrical machine to play with like everyone else. He repeated the experiments of those he heard and learned about; e.g., Bose, Krueger, and Winkler. His goal was to increase the strength and reliability of the electrical flare flaunted by Bose. Von Kleist had erred, however, by thinking that the flares or sparks were proportional to the mass of the materials being electrified (greater the spark or schlag would be with the larger prime conductors of electrical machines).
So while experimenting with his electrical machine and trying to achieve his goal he apparently connected the machine’s prime conductor to a metal wire at one end, and placed the other end into a jar filled with water. He had insulated the jar after reading Charles Dufay, a French scientist, and believed the addition to the jar would increase the spark. He was amazed (shocked)! By holding the jar in one hand while charging the jar with an electrical machine he acted as ground which in turn allowed the nail in the jar to serve as a positive pole.
He made his discovery in October, and began writing letters about his discovery on 4 November 1745. He wrote to Dr. Lieberkuhn a famous physician, physicist, and member of the Berlin Academy who later reported the event to the Berlin Academy. His next letter went to Mr. Paul Swiettiki of Denmark on 28 November, and then to Professor Johann Krueger of Halle in December. Other letters were sent to Winkler of Leipzig, and a professor at the Academy of Lignitz.
Krueger published von Kleist’s experiment in Geschichte der Erde, Halle, 1746. All of the recipients of these letters were said to have replied that they were unsuccessful in replicating the experiment, or that his experiment was amazing. The letters contained an account of von Kleist’s experiment in which he inserted an iron nail through the cork placed in the neck of a hand held glass jar.
The jar probably contained alcohol, mercury, or water. Von Kleist connected the nail to his electrical machine and then electrified it. Touching the nail with the other hand, he received a severe shock. He was surprised that shocks were obtained only when he held the jar with both hands (closed circuits were unknown at that time), but when touching only the nail placed in the charged jar nothing happened.
He claimed that his arm and shoulder of the hand holding the nail were numbed by the shock, and stated that not even Professor Bose would have liked a second kiss from the jar. Touching the charged nail of the jar to another object produced a strong spark as the jar discharged the electricity that it had stored.. Von Kleist had written to five individuals, and when they received additional information from him about his experiment they failed again.
Between his first terrifying experiment and the time that he wrote the letters von Kleist had also discovered that when he removed the electrified jar from the electrical machine the spark appeared and remained long enough to provide some observable light in the room. He stated that he walked around the room many times with the light. Speculation has him adding alcohol to the jar so that the spark lighted the fuel for his light. He had produced the flare of Bose, but in a different fashion and more convincing manner.
Mr. Swietlicke shared his copy of von Kleist’s letter with fellow countryman Daniel Gralath who also failed to successfully replicate the experiment. Requesting additional information Gralath was informed that a metal wire served better than a nail, and that a barometric tube was better than a medicine phial. On 5 March 1746, Gralath succeeded in replicating the experiment. By this time, however, news from Leyden about Professor Musschenbroek’s experiment had reached scientists in several countries.
The claim for creation of the Leyden jar is uncertain. Some writers give claim to von Kleist, while some claim that van Musschenboek was the real inventor. Actually, both of them made the same discovery independently and almost simultaneously. In November 1745, Ewald von Kleist, a German clergyman and scientist, and in January 1746 Petrus van Musschenbroek, a Dutch professor, discovered the magical condenser. This condenser or capacitor as it is now called was first named after professor Musschenbroek’s hometown and university (Leiden or Leyden, Netherlands) by Abbe Nolett, a French scientist, who coined the term Leyden jar. The jar was once called the Kleistian jar, after von Kleist, but this term was not lasting.
The jar, at the time of its discovery and afterward, offered new avenues of study for scientists, and they responded accordingly. The Leyden jar was adopted by electrotherapists, and by 1752 there were almost as many publications of its use in medicine as there were for its use in others areas. Use of the Leyden jar in medicine continued to increase over the years so that in 1789 there were 70 applications in medicine ascribed in publications while only 30 publications addressed its physical aspects. Although its use for entertainment tarnished its creditability somewhat, scientists continued their investigations involving the Leyden jar. Scientists had to learn the concepts of charge, current (movement), potential difference (force moving charge), and capacitance before completely accepting it as a tool in research.
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