9781422277652

Models of crystals prepared by Pasteur in his work on the relationship between crystalline form, chemical composition, and the direction of rotatory polarization.

the plane of polarized light at all. Pasteur wanted to find out more about this substance. No one knew why it differed from tartaric acid in failing to polarize the light passed through it. This is typical of the kind of problem that Pasteur studied during the next few years. Another problem Pasteur was interested in was dimorphism . Some substances produce different kinds of crystals if different methods of preparation are used. For example, sulfur melted in a crucible produces crystals that are quite unlike those obtained from solutions of sulfur in carbon disulphide. Such substances are called “dimorphic,” and Pasteur studied the reasons why the different forms occur. During the revolutionary year of 1848, Pasteur found himself in Paris. He joined the National Guard, and in an outburst of enthusiasm, gave all his savings to the cause of the Republic. Meanwhile he continued his work as a teacher and on his research in chemistry. His absorption in the problem of tartaric acid soon bore fruit. He discovered that racemic acid was made up of two kinds of crystals, which differed in only one

13