However, the head-master, Romanet, appears to have possessed more discernment than the rest of the faculty; for he frequently engaged young Pasteur in private talks in which he endeavored to arouse in him the ambition to prepare for teaching as a career.
At graduation, he was offered the position of preparation assistant or coaching tutor to the younger pupils, a post which carried the munificent salary of 300 francs per annum with board and lodging. He accepted the position gladly; and, with charming modesty, expressed the conviction that the salary was much beyond his deserts.
Small as his salary was, still he managed to save out of it something to help educate his sisters. Meanwhile he worked hard on the studies required for his B.S. degree, a prerequisite to his entering the Ecole Normale Supérieure at Paris. On this examination he was graded "mediocre" in chemistry.
Pasteur had thus far been a hard student; but he does not appear to have been an enthusiastic one till he had been for some time at the École Normale under the instruction of Balard, the discoverer of bromine, who was probably the only real teacher he ever had.
But even in this highest school for the training of professors afforded by the France of that day, the scientific equipment was so meager that only a few simple experiments were allowed for repetition by the students of chemistry. An incident in this connection will show the stuff that Pasteur was made of. Not content with being told how phosphorus is prepared, he bought some bones, calcined them, treated the calx with sulphuric acid, distilled the product with charcoal, and placed the distillate in a vial neatly labelled phosphorus. This was his first scientific joy. His comrades dubbed him "the laboratory pillar."
About this time he was shown a sample of a strange new acid of the same composition as tartaric acid, but manifesting strikingly different physical characteristics. His curiosity was intensely aroused.
Tartaric acid had been discovered in the "tartar" of wine casks by Scheele, of Sweden, in 1770. Thann, an Alsatian manufacturer of tartaric acid, discovered some of the anomalous variety in the output of his factory in 1825. He was unable to reproduce it. It was studied by Gay Lussac and Berzelius in 1826. The latter proposed for it the name of paratartaric acid; the former suggested that it be called racemic acid. Mitscherlich, of Berlin, in 1844 reported it as isomorphic with tartaric acid; and discovered that while the latter rotates a beam of polarized light to the right, racemic acid is inactive in this respect.
These were the facts brought to Pasteur's attention at the time when he was shown a specimen of the acid. Although immensely interested in the mystery presented by racemic acid, he put it aside, resolving to take it up when through with the final examination of his course of study, an ordeal for which he was just then preparing.