Editing 1821 in science (section)

==Chemistry==
* [[John Kidd (chemist)|John Kidd]] describes the properties of the substance which he calls ''[[naphthalene|naphthaline]]''.<ref>{{cite journal|first=John|last=Kidd|year=1821|title=Observations on Naphthaline, a peculiar substance resembling a concrete essential oil, which is apparently produced during the decomposition of coal tar, by exposure to a red heat|journal=[[Philosophical Transactions of the Royal Society]]|volume=111|pages=209–221|doi=10.1098/rstl.1821.0017|s2cid=97798085}}</ref>
* [[Pierre Jean Robiquet]], [[Joseph Bienaimé Caventou]] and [[Pierre Joseph Pelletier]] isolate [[caffeine]].