...in which we learn how polarized light helped Louis Pasteur to determine that internal three-dimensional structure of molecules was real based on "optical isomers." We then move to the 1870s, and see how van 't Hoff and Le Bel independently came up with the idea of tetrahedral carbon to explain optical isomers. Once the idea of an actual 3D structure for molecules was accepted, a variety of chemists used this idea to explain all sorts of molecular structures. Supporters of this podcast at https://www.patreon.com/thehistoryofchemistry can download a supplementary sheet with some diagrams.Support the show