Menthone Glycerin ethereal History

Menthone Glycerin ethereal was first described by Moriya in 1881.It was then synthesized by heating menthol withchromic acid.
Menthone Glycerin ethereal was crucial to one of the great mechanistic discoveries in organic chemistry. In 1889, Ernst Beckmann discovered that dissolving Menthone Glycerin ethereal in concentrated sulfuric acid gave a new ketonic material. Coincidentally, the product gave an equal but opposite optical rotation to the starting material.
The tetrahedral carbon having been recognized for only 15 years at that time, Beckmann realized that this must result from an inversion of configuration at the asymmetric carbon atom next to the carbonyl group (at that time thought to be carbon attached to the methyl, rather than the isopropyl group), and he postulated this as happening through the intermediacy of an enol tautomer in which the asymmetric carbon atom was of trigonal (planar) rather than of tetrahedral geometry.
This was an early example of the inference of an (almost) undetectable intermediate in a reaction mechanism accounting for the outcome of the reaction.