Louis Pasteur

5x puncte

categorie: Fizica

nota: 9.87

nivel: Liceu

Death is more familiar to me than I care to think... three of my daughters.. .my father.." I have been thinking all day of the marks of affection I have had from him. For thirty years I had been in his constant care, I owe everything to him. When I was young he kept me from bad company and instilled into me the habit of working and the most loyal and best filled life. He was far above his position[...]
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Death is more familiar to me than I care to think... three of my daughters.. .my father.." I have been thinking all day of the marks of affection I have had from him. For thirty years I had been in his constant care, I owe everything to him. When I was young he kept me from bad company and instilled into me the habit of working and the most loyal and best filled life. He was far above his position (tanner) both in mind and in character. The touching part of his affection for me is that it was never mixed with ambition...and yet, I am sure that some of the success in my scientific career must have filled him with joy and pride..."(Vallery-Radot, 119)

Science...it is my life..it has brought me a deepness of pleasure that I have always known yet never realized. I remember when I was working on the tartrates, tartaric acid and racemic acid or paratartrate. Tartaric acid was known to rotate light to the right, whereas paratartrate, odly enough, did not affect light in the least. "The fortunate idea came to me to orient my crystals with reference to a plane perpendicular to the observer, and then I noticed that the confused mass of crystals of paratartrate could be divided into two groups according to the orientation of their facets of symmetry.

In one group, the facet of symmetry nearer my body was inclined to my right with reference to the plane of orientation which I just mentioned, whereas the facet of asymmetry was inclined to my left in the other. The paratartrate appeared as a mixture of two kinds of crystals, some asymmetric to the right, some asymmetric to the left.

A new and obvious idea soon occured to me. These crystals asymmetric to the right, which I could separate manually from the others, exhibited an absolute identity of shape with those of the classical right tartrate. Pursuing my preconceived idea, in the logic of its deductions, I separated these right crystals from the crystallized paratartrate; I made the lead salt and isolated the acid; this acid appeared absolutely identical with the tartaric acid of grape, identical also in its action on polarized light.

My happiness was even greater the day when, separating now from the paratartare the crystals with asymmetry at their left, and making their acid, I obtained a tartaric absolutely similar to the tartaric acid of grape, but with an opposite asymmetry, and also with an opposite action on light. Its shape was identical to that of the mirror image of the right tartaric acid and, other things being equal, it rotated light to the left as much in absolute amount as the other acid !
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