A fascinating letter with significant scientific content, providing material for an article in the French newspaper La Revue.
Pasteur begins by providing Drion with a curriculum vitae up to the end of 1854:
- Louis Pasteur was born in Dole (Jura) on the 27th of December1822
- Commenced studies at the University on the 27th of December 1840 and served as teaching assistant at the Royal High School of Besançon
- Attended the prestigious school for higher education in Paris École Normale Supérieure from 1843-1846
- Became an Associate Professor of Physical Science in September 1846
- On the 1st of October 1846, appointed Tutor in Chemistry at the Ecole Normale Supérieure
- Earned an PhD in Physical Science on 23rd August 1847
- Appointed Professor of Physics at the High School of Dijon on 16th September 1848
- Made responsible for the chemistry courses at the Faculty of Sciences of Strasbourg on the 29th of December 1848.
- Appointed Professor of Chemistry on the 9th of November 1852
- Appointed Dean of the Faculty of Science of Lille on the 9th of December 1854.
- Appointed Knight of the Legion of Honour on the 12th of August 1853.
Next, Drion is given a summary of Pasteur’s method of working:
Discoveries in molecular chemistry led to the most favourable academic reports. What distinguishes the work from the results is the scientist’s method. He debated the difficult problems of the molecular constitution of natural organic products by taking the chemical studies of the resources of physics and crystallography into consideration.
Pasteur then summarizes his work on asymmetry and optical activity, which was his principal area of research in the period 1847-57:
All objects are grouped into two large categories depending on their shape. The objects in the first category have a shape that is stackable. The objects in the second category are not stackable. They do not fit each other, just like a glove for the right hand is not suitable for the left hand. However, Mr Pasteur has recognised that the shape of all the natural substances, meaning those which have been developed under the influence of plant life, are asymmetrical like a hand or a spiral staircase. According to scientific research, asymmetry certainly occurs. The elementary atoms form groups within the individual molecule, but this asymmetry of organic individuals is not a necessary condition of the existence of the molecule. You can make it disappear or turn it into the opposite of what it is, almost as if the steps of a spiral staircase were replaced by a straight staircase or one in the opposite direction. One of the most important discoveries in Mr Pasteur’s research is the discovery of the remarkable relations that exist between the phenomenon of the rotatory polarisation and the asymmetric constitution of the organic molecules.
“In Pasteur’s early work as a chemist, beginning at the École Normale Supérieure, and continuing at Strasbourg and Lille, he examined the chemical, optical and crystallographic properties of a group of compounds known as tartrates. He resolved a problem concerning the nature of tartaric acid (1848). A solution of this compound derived from living things (specifically, wine lees) rotated the plane of polarization of light passing through it. The mystery was that tartaric acid derived by chemical synthesis had no such effect, even though its chemical reactions were identical and its elemental composition was the same. Pasteur was able to show not only that optical activity related to the shape of the crystals, but also that an asymmetric internal arrangement of the molecules of the compound was responsible for twisting the light. The (2R,3R)- and (2S,3S)- tartrates were isometric, non-superposable mirror images of each other. This was the first time anyone had demonstrated molecular chirality, and also the first explanation of isomerism” (Wikipedia). “Pasteur rose to the status of a national hero during his lifetime. However, perhaps surprisingly, Geison, a historian who has made a detailed study of Pasteur’s life and work, is able to state: ‘His contributions to basic science were extensive and very significant, but less revolutionary than his reputation suggests. Pasteur’s most profound and most original contributions to science [i.e. these are the ones in the field of molecular chirality and crystallography] are also the least famous, and they came at the very outset of his career.’ Bernal, a crystallographer, concurs ‘ . . . his first and in some ways his greatest scientific discovery’” (Flack, p. 371).
Charles Alexandre Drion (1827-63) was educated at the Ecole Normale Supérieure, graduating in 1847. From 1854 to 1859 he was Professeur de Physique at the Lycée de Versailles. He earned his doctorate in 1859 with a thesis entitled ‘Recherches sur la dilatabilité des liquides volatils.’ The following year he was appointed Chargé de Cours at the University of Besançon, rising to professor in 1862.
Flack, ‘Louis Pasteur’s discovery of molecular chirality and spontaneous resolution in 1848, together with a complete review of his crystallographic and chemical work,’ Acta Crystallographica A65 (2009), 371-89.
One leaf (209 x 268 mm) vertical folded, just over 2½ pages of writting. Very well preserved. Full transcription and English translation of the letter is included.