“You remember what I used to say to you and to M. Dumas, that almost certainly the first operation which tartar goes through in certain factories causes it to lose all or nearly all its racemic acid. Well, in the two Viennese factories, it is only two years since they began to operate on crude tartar, and it is only two years since they first saw the supposed sulphate of potash, the supposed sulphate of magnesia. For, at M. Seybel’s, they had taken for sulphate of magnesia the little crystals of racemic acid. “Shortly, this is as far as I have come--I spare you many details:-- 1. “The Naples tartar contains racemic acid. 2. “The Austrian tartar (neighbourhood of Vienna) contains racemic acid. 3. “The tartars of Hungary, Croatia, Carniola contain racemic acid. 4. “The tartar of Naples contains notably more than the latter, for it presents racemic acid even after one refining process, whilst that from Austria and Hungary only presents it when in the crude state. “I believe it now to be extremely probable that I shall find some racemic acid in French tartars, but in very small quantities; and if it is not detected it is because all the circumstances of the manufacture of tartaric acid are unknown or unappreciated, or because some little precaution is neglected that would preserve it or make it visible. “You see, dear Marie, how useful was my journey.” “_Vienna, September 30, 1852._ I am not going to Trieste; I shall start for Prague this evening.” “_Prague, October 1, 1852._ Here is a startling piece of news. I arrive in Prague; I settle down in the Hôtel d’Angleterre, have lunch, and call on M. Rochleder, Professor of chemistry, so that he may introduce me to the manufacturer. I go to the chemist of the factory, Dr. Rassmann, for whom I had a letter from M. Redtenbacher, his former master. That letter contained all the questions that I usually make to the manufacturers of tartaric acid. “Dr. Rassmann hardly took time to read the letter; he saw what it dealt with, and said to me: ‘I have long obtained racemic acid. The Paris Pharmaceutical Society offered a prize for whoever manufactured it. It is a product of manufacture; I obtain it with the assistance of tartaric acid.’ I took the chemist’s hand affectionately, and made him repeat what he had said. Then I added: ‘You have made one of the greatest discoveries that it is possible to make in chemistry. Perhaps you do not realise as I do the full importance of it. But allow me to tell you that, with my ideas, I look upon that discovery as impossible. I do not ask for your secret; I shall await the publication of it with the greatest impatience. So that is really true? You take a kilogramme of pure tartaric acid, and with that you make racemic acid?’ “‘Yes,’ he said; ‘but it is still’ ... and as he had some difficulty in expressing himself, I said: ‘It is still surrounded with great difficulties?’ “‘Yes, monsieur.’