Louis Pasteur (1822-1895) / by E.J. McWeeney.

  • McWeeney, Edmond J. (Edmond Joseph), 1864-1925.
Date:
[1912]
Catalogue details

Licence: In copyright

Credit: Louis Pasteur (1822-1895) / by E.J. McWeeney. Source: Wellcome Collection.

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    work took him from four in the morning till nine at night; but what was the labour compared with the joy of possessing sixty grammes of pure phosphorus of his own manufacture! Endowed by God with such a spirit as this, it was not surprising that Pasteur should be selected by his superiors for promotion. He passed his Licence examination, and then the higher one called the Agrdgalion with special distinction in physics and chemistry. This was in 1846. A few months later the Minister of Public Instruction wanted to make him Professor of Physics at a Lycee at Tournon, but his teacher, the eminent Balard (discoverer of bromine), represented that it would be rank folly to bury so promising a talent in the provinces, and suc¬ ceeded in having the appointment cancelled. Pasteur, left to his laboratory work, at once proceeded to prepare for his final degree of Doctor of Science by undertaking some investigations on the application of crystallography and physics to chemical problems. He prepared a thesis on “ The Phenomena relative to the Rotatory Polarization of Liquids,” and duly obtained his Doctorate in 1847. His attention became concentrated on the optical properties of certain crystalline substances by virtue of which some of them rotate the plane of polariza¬ tion to the right, whilst others do so to the left. In 1844 a distinguished German-chemist, Mitscherlich, had dis¬ covered that the two varieties of tartaric acid possessed different optical properties. (Here I may explain that this is the acid obtained from the crusty deposits called “ tartar ” in old wine barrels.) The common variety (ordinary tartaric acid) rotates the plane of polarized light to the right, whilst the rarer sort (para-tartaric or racemic acid) possesses no rotatory power. Pasteur, who had been studying crystallography and had acquired skill in the use of the goniometer, was much interested in Mitscherlich’s discovery. He prepared a fine set of crystals of tartaric acid and its compounds. He could 184