Template:Selected anniversaries/April 20: Difference between revisions

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||1871: Slavoljub Eduard Penkala born ... engineer, invented the mechanical pencil. Pic.
||1871: Slavoljub Eduard Penkala born ... engineer, invented the mechanical pencil. Pic.
||1899: Charles Friedel dies ... chemist and mineralogist. riedel developed the Friedel-Crafts alkylation and acylation reactions with James Crafts in 1877, and attempted to make synthetic diamonds. Pic.


File:Curie_and_radium_by_Castaigne.jpg|link=Radium (nonfiction)|1902: Pierre and Marie Curie refine [[Radium (nonfiction)|radium chloride]].
File:Curie_and_radium_by_Castaigne.jpg|link=Radium (nonfiction)|1902: Pierre and Marie Curie refine [[Radium (nonfiction)|radium chloride]].

Revision as of 06:27, 11 March 2019