Editing Leyden jar (section)

== Storage of the charge ==
[[file:Dissectible Leyden jar.png|thumb|upright=0.4|"Dissectible" Leyden jar, 1876]]
It was initially believed that the charge was stored in the water in early Leyden jars. In the 1700s American statesman and scientist [[Benjamin Franklin]] performed extensive investigations of both water-filled and foil Leyden jars, which led him to conclude that the charge was stored in the glass, not in the water. A popular experiment, due to Franklin, which seems to demonstrate this involves taking a jar apart after it has been charged and showing that little charge can be found on the metal plates, and therefore it must be in the [[dielectric]].  The first documented instance of this demonstration is in a 1749 letter by Franklin.<ref>Letter IV: Benjamin Franklin to Peter Collinson, April 29, 1749 (Bigelow vol II p. 237-253) [http://www.compadre.org/precollege/items/Load.cfm?ID=3430 (PDF containing extracts)]</ref>  Franklin designed a "dissectible" Leyden jar ''(right)'', which was widely used in demonstrations. The jar is constructed out of a glass cup nested between two fairly snugly fitting metal cups. When the jar is charged with a high voltage and carefully dismantled, it is discovered that all the parts may be freely handled without discharging the jar. If the pieces are re-assembled, a large [[electric spark|spark]] may still be obtained from it.

This demonstration appears to suggest that [[capacitor]]s store their charge inside their dielectric. This theory was taught throughout the 1800s. However, this phenomenon is a special effect caused by the high voltage on the Leyden jar.<ref name="Mills">{{cite journal | last = Mills | first = Allan | title = Part 6: The Leyden jar and other capacitors | journal = Bulletin of the Scientific Instrument Society | issue = 99 | pages = 20–22 | date = December 2008 | url = http://www.sis.org.uk/bulletin/99/mills.pdf | access-date = 2010-06-13 | url-status = dead | archive-url = https://web.archive.org/web/20110727024546/http://www.sis.org.uk/bulletin/99/mills.pdf | archive-date = 2011-07-27 }}</ref> In the dissectible Leyden jar, charge is transferred to the surface of the glass cup by [[corona discharge]] when the jar is disassembled; this is the source of the residual charge after the jar is reassembled. Handling the cup while disassembled does not provide enough contact to remove all the surface charge. [[Soda glass]] is [[hygroscopic]] and forms a partially conductive coating on its surface, which holds the charge.<ref name="Mills" /> Addenbrooke (1922) found that in a dissectible jar made of paraffin wax, or glass baked to remove moisture, the charge remained on the metal plates.<ref>{{cite journal | last = Addenbrooke | first = G. L. | title = A study of Franklin's Experiment on the Leyden jar with movable coatings | journal = Philosophical Magazine |series=6th Series | volume = 43 | issue = 255 | pages = 489–493 |date=March 1922 | doi = 10.1080/14786442208633901 | url = https://zenodo.org/record/1430973 }}</ref> Zeleny (1944) confirmed these results and observed the corona charge transfer.<ref>{{cite journal | last = Zeleny | first = John | title = Observations and Experiments on Condensers with Removable Coats | journal = Am. J. Phys. | volume = 12 | issue = 6 | pages = 329–339 |date=December 1944 | doi = 10.1119/1.1990632 |bibcode = 1944AmJPh..12..329Z }}</ref>

If a charged Leyden jar is discharged by shorting the inner and outer coatings and left to sit for a few minutes, the jar will recover some of its previous charge, and a second spark can be obtained from it.<ref>{{cite EB1911| wstitle = Electrostatics | volume = 9 | page = 246  |first=John Ambrose |last=Fleming}}</ref> Often this can be repeated, and a series of 4 or 5 sparks, decreasing in length, can be obtained at intervals. This effect is caused by [[dielectric absorption]].<ref>{{cite book | last = Graf | first = Rudolf F. | title = Modern dictionary of electronics, 7th Ed. | publisher = [[Newnes]] | year = 1999 | pages = 192 | url = https://books.google.com/books?id=uah1PkxWeKYC&pg=PA192 | isbn = 978-0-7506-9866-5}}</ref>