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a great advance, apparently unrealizable, remained yet to be 

 accomplished. Could not racemic acid be produced by the, aid 

 of tartaric acid ? 



Pasteur himself, as he told the optimist Eassmann, did not 

 believe such a transformation possible. But, by dint of in- 

 genious patience, of trials, of efforts of all sorts, he fancied he 

 was nearing the goal. He wrote to his father : " I am think- 

 ing of one thing only, of the hope of a brilliant discovery which 

 seems not very far. But the result I foresee is so extraordinary 

 that I dare not believe it." He told Biot and Senarmont of 

 this hope. Both seemed to doubt. " I advise you," wrote 

 Senarmont, "not to speak until you can say: 'I obtain 

 racemic acid artificially with some tartaric acid, of which I 

 have myself verified the purity ; the artificial acid, like the 

 natural, divides itself into equal equivalents of left and right 

 tartaric acids, and those acids have the forms, the optical pro- 

 perties, all the chemical properties of those obtained from the 

 natural acid.' Do not believe that I want to worry you; the 

 scruples I have for you I should have for myself ; it is well to 

 be doubly sure when dealing with such a fact." But with 

 Biot, Senarmont was less reserved ; he believed the thing done. 

 He said so to Biot, who, prudent and cautious, still desirous of 

 warning Pasteur, wrote to him on May 27, 1853, speaking of 

 Senarmont : " The affection with which your work, your per- 

 severance and your moral character have inspired him makes 

 him desire impossible prodigies for you. My friendship for 

 you is less hastily hopeful and harder to convince. However, 

 enjoy his friendship fully, and be as unreserved with him as 

 you are with me. You can do so in full security ; I do not 

 know a stronger character than his. I have said and repeated 

 to him how happy I am to see the affection he bears you. 

 For there will be at least one man who will love you and under- 

 stand you when I am gone. Farewell ; enough sermons for 

 to-day ; a man must be as I am, in his eightieth year, to write 

 such long homilies. Fortunately you are accustomed to mine, 

 and do not mind them." 



At last, on the first of June, here is the letter announcing 

 the great fact : " My dear father, I have just sent out the 

 following telegram : Monsieur Biot, College de France, Paris. 

 I transform tartaric acid into racemic acid; please inform MM. 

 Dumas and Senarmont. Here is at last that racemic acid 

 (which I went to seek at Vienna) artificially obtained through 



