Technikatörténeti szemle 19. (1992)

KÖNYVISMERTETÉS - Papers of the First „MINERALKONTOR” International Conference on the History of Chemistry and Chemical Industry (Veszprém, 12-16 August, 1991)

Another disadvantage was that many of these instruments barely penetrated the ultraviolet region which was becoming of increasing interest to analytical chemists. Ultraviolet absorption spectrometry: Out of the light and into the dark Prior to 1941 almost all ultraviolet absorption spectra had been measured by photographic means. The earliest systematic studies were made by Victor Henri and his students. Henri earned a Ph. D. in psychology from Gottingen in 1897 and was the collaborator and assistant of Alfred Binet, with whom he cofounded the first French journal in experimental psychology. But by 1900 he turned to chemistry, and was a professor of chemistry at the University of Zurich from 1919 to 1930. His first paper in 1914, while he was at the Sorbonne, began a long series in which he established the spectra of a number or organic compounds, showing that the spectrum was not a function of the whole molecule but only of a particular atomic grouping within the molecule. He extended the use of the term chromophore into the ultraviolet region. Robert Woodward's 1941 paper drew extensively on Henri's investigations. The 1930s was a period of intensive interest in the use of absoprtion spectra for analytical purposes. But measurements in the ultraviolet were still very difficult, both from a measurement standpoint and in producing a reliable source of ultraviolet light. In addition to the hydrogen discharge tube for continuous source of ultraviolet, one method was to use an underwater spark, coupled with a Hilger sector photometer and a Bausch and Lomb spectrograph. These difficulties prompted several workers to construct their own apparatus. In 1937 T. R. Hogness of the University of Chicago revealed an apparatus that could replace the photographic apparatus which was, according to Hogness, ..inordinately slow and usually of insufficient precision (8)." The Hogness instrument covered the entire ultraviolet, but was developed primarily for analytical purposes where only one wavelength was required rather than a measurement of the entire spectrum. Since he could do an analytical measurement in about one minute, Hogness minimized the need for an automatic recording instrument, indicating that it „would not be worth the necessary experimentation and expense." Hogness was financially supported by a grant from the Rockefeller Foundation for the Application of Spectroscopic Methods to Biological Problems and used his instrument for the identification and analysis of ..biologically potent substances." Indeed, biological applications were just one area where ultraviolet analyses were becoming very important. For example, Vitamin A analyses had been made by a lengthy and tedious animal assay method. By 1930 it was recognized that the analysis of Vitamin A was readily accomplished by an ultraviolet measurement at 328 nm, and absorption methods were developed. By 1937 GM Laboratories was marketing a Vitamin A meter that was the first to use a photoelectric detector (9). By its very nature, however, this meter was only useful for measurements at the one specific wavelength. In their history of analytical chemistry H. A. Laitinen and G. W. Eving have remarked that „the historical impact of the model DU was as significant in