received his Ph.D. in 1918 from the University of Chicago, where he studied
with William D. Harkins. Clark held several academic positions, most notably
as an assistant professor of Applied Chemical Research at the Massachusetts
Institute of Technology. In 1927 he joined the faculty of the University
of Illinois in its analytical chemistry division, where his students knew
him as "G. L."
Clark was the leading exponent of the application of X-ray analyses to
a wide variety of materials, including metals and minerals, natural and
synthetic fibers, natural and synthetic rubber, clays, carbon black, storage
battery plates, corks, and waxes. He was a pathfinder in recognizing the
connection between instrumentation and analysis, and he frequently introduced
newly developed instrumental methods into the research community.
Clark was an expert in the application of X-rays in science, industry,
and medicine. He used X-rays in stress analysis, determining whether particular
metals (such as those used in propellers) were defective. In 1945 he developed
an X-ray tube that could withstand the heat generated by up to 50,000
volts of electricity. Clarks new tube meant that X-ray pictures
could be taken in seconds rather than minutes, giving growth to the medical
uses of X-rays.
Clark successfully characterized the macromolecules found in the rubber
plant, determining their molecular weight, an issue that had intrigued
botanists for years. He also discovered that rubber crystallizes when
it is stretched, opening up a new field of X-ray studies.
In 1952 the first consolidated X-ray facility in the United States was
dedicated at the University of Illinois. A plaque acknowledged Clarks
twenty-five years of applied X-ray research. In 2000 the X-ray facility
was rededicated as the G. L. Clark X-ray Laboratory.