Letter from Richard Willstatter, Eidgenossische Technische Hochschule to Michael Heidelberger

To qualify for a desirable academic position in chemistry in the United States, scientific training at a European University was an indispensable credential before World War I. With financial support from his father, Heidelberger spent the year 1911-1912 in the laboratory of the organic chemist and 1915 Nobel Laureate, Richard Willstatter, at the Federal Polytechnic Institute in Zurich, Switzerland. There, Heidelberger helped prepare cyclooctatetraene, the next higher analog of benzene, consisting of a ring with eight carbon atoms and four double bonds, a relatively reactive, colorless liquid used in organic chemistry research. As Heidelberger recalled, it was in Willstatter's laboratory that he "really began to learn how to deal with difficult things in chemistry." "Better training than that you couldn't have . . ."

In this letter of reference, Willstatter commends Heidelberger for his "extraordinary effort," and "as a hard-working chemist and as a young researcher of absolute reliability. His precision during observations and measurements also made a positive difference during physical [chemistry] investigations."