Chemistry

CHEMISTRY

New Elements and Substances

In chemistry in the 1930s most of the holes on Dmitry Ivanovich Mendeleyev's periodic table of chemical elements were filled. Emilio Segre, working from the foundation of demonstrations carried out by Robert Oppenheimer, tracked down the element with atomic number 43, technetium, which turned out to be the simplest element with no isotope. Only the elements for atomic numbers 61, 85, and 87 were missing, with 87 being discovered by French chemist Marguerite Perey in 1939 and named francium for her native country. Work on discovering stable isotopes to various elements also continued. In 1931 Harold Urey was able to isolate an isotope of hydrogen with one proton and one neutron, which was named deuterium. In 1935 physicist Arthur Jeffrey Dempster showed that uranium has one isotope occurring in one out of 140 atoms, uranium 235. This substance would become essential to the manufacture of the first atomic bomb.

Vitamins

Several vitamins and substances were either discovered to exist or were successfully synthesized during the 1930s. Vitamins had been known since the 1900s, but despite their use in nutrition and medicine their molecular structure remained unknown. This changed in 1930 when the Swiss chemist Paul Karrer synthesized vitamin A, which resembles half a molecule of carotene. Two years later American biochemist Charles Glen King claimed that he had discovered vitamin C; however, within weeks biochemist Albert Szent-Gydrgyi claimed the same result with hexuronic acid. Although the latter was the correct form, the controversy raged on while the two were still alive. In 1933 British chemist Sir Norman Haworth synthesized vitamin C and named it ascorbic acid; he later received the Nobel Prize for his effort. In 1936 Roger J. Williams was able to synthesize vitamin B, found in rice and used to prevent beriberi. In 1939 Edward Adelbert Doisy, working from studies done by Danish scientist Carl Peter Henrik Dam, was able to synthesize vitamin K, a substance essential to blood coagulation, for the first time.

The Nature of Enzymes

American chemists also made great progress in isolating enzymes during the 1930s. The crystallization process, by which a liquid solution is saturated, thus forming crystals, was difficult—its first success dated to 1926—yet essential in determining the nature of enzymes, because when successful, it allowed a more precise identification of the substance under investigation. In 1930 John Howard Northrop was able to crystallize a digestive enzyme named pepsin, and he showed it to be a protein. His success inspired biochemist Wendell Stanley to use a similar technique to define the structure of viruses. He started work by growing tobacco and infecting it (the tobacco mosaic virus was the first recognized as a virus in the late nineteenth century). He then mashed the leaves and put them through the same procedures as those used to extract enzymes. In 1935 he isolated fine crystals with the same properties as the virus. He thus proved that crystallization was not a life-ending process and that viruses were such a simple life form that they could live in a crystalline state. In the field of hormone research Edward Kendall isolated twenty-eight different cortical hormones and selected the most effective compounds for tests. One of them, isolated as compound E, showed remarkable results in fighting inflammations and became known as cortisone.

Industry and Research

In 1930 about 945 science doctorates were conferred in the United States, including 332 in chemistry and 109 in physics. Ten years later the overall number in doctorates conferred would reach 1,452, with a slight increase in the percentage of chemistry degrees (33.4 percent or 532 degrees) and a decrease in physics degrees (9 percent or 132, down from 11.5 percent). Such numbers reflect the strong influence of chemistry in American science. The predominance of the discipline was further confirmed by the number of prestigious awards going to chemists as well as the naming of such scientists to high academic posts. Furthermore, the trend toward the formation of chemical laboratories in the 1920s continued in the 1930s thanks to the support of the chemical-process industries. Between 1927 and 1938, for example, the number of research workers at Dow Chemical jumped from one hundred to five hundred, while those in the petroleum industry increased from several hundred to more than five thousand in the same period,

Professionalization

As the number of chemists grew, so did specializations. The 1930s witnessed the creation of two new associations, thus further recognizing subspecialties in the field: the American Society of Brewing Chemists was formed in 1934, followed a year later by the American Microchemical Society. A new publication, the Journal of Organic Chemistry, was established in 1936, thus becoming the eleventh American chemistry journal since the appearance of the Journal of the American Chemical Society in 1876. (Of those, six were founded in the 1920s.) The 1930s, especially the later part of the decade, thus witnessed a jump in the professionalization of the field.

INCREASED USE OF THE REFRIGERATOR

Early refrigeration units used ammonia and sulfur dioxide to lower temperature through evaporation. These substances were quite dangerous, however, and a search for a stable and odorless liquid was pursued. American chemist Thomas Midgley had discovered such a liquid in 1921, but it was not until 1930 that he synthesized a substance with these properties. Trademark uses were established, and such products as Freon, deemed completely safe at the time, went on sale and were used in refrigeration units. A 1931 survey by twenty leading refrigerator manufacturers revealed that three million Americans protected their food through the use of electric refrigerators. In 1930 1,002,000 refrigerators were sold. Of these, 770,000 were household refrigerators sold for a total of $223,320,000, or approximately 31 percent of the value of all household electric appliances. Nevertheless, these impressive numbers paled when compared to the number of American homes actually equipped with refrigerators: 14.7 percent, mostly in urban areas already served by electric power plants.

Source:

F. D. McHugh, "The Scientific American Digest," Scientific American, 144 (May 1931): 350.

Source:

Arnold Thackray and others, Chemistry in America 1876-1976 (Hingham, Mass.: Kluwer Academic Publishers, 1985).