A New Spectroscopy Laboratory

As time went on I worked more on the spectrographic analysis of materials. Back in 1922, Meggers, Kiess and Stimson had published a basic paper on ‘Practical Spectrographic Analysis” and Meggers continued to encourage the development of this new tool for chemical analysis. In 1933 the opportunity arose to expand the analytical work with a laboratory in the Chemistry Building. The space there had been devoted to research on improvement of photographic emulsions under Dr. Burt H. Carroll as part of the Spectroscopy Section. With the severe reduction of Bureau funds as the depression grew worse, and with same pressure from the outside, this effective research program was closed down. Carroll, with assistant Charles M. Kretchman moved to the Eastman Kodak Co. in one of the many Bureau spin-offs that became apparent over the years; Dr. Donald Hubbard, the third member of the group remained at the Bureau, transferring to research in the Glass Section. 

I was put in charge of this laboratory which now was applied to expanded work in spectrographic analysis. It was necessary first to build a high-dispersion grating spectrograph as none was yet available commercially, and to add other equipment for excitation of spectra and for measuring spectral line intensities. In the following years analyses were made mostly for the Bureau’s Chemistry and Metallurgy Divisions but also for outside U.S. Government agencies which did not yet have spectrographic facilities. Some examples were the FBI (evidence material), the Treasury Department (proof gold) and the Department of Agriculture (discovery of rare earth elements in hickory leaves). 

One of the first applications for our Chemistry Division was the analysis of the metallic element gallium, which was under purification by Dr. James I. Hoffman. Much spectrographic analysis was required and this resulted in a joint publication in 1935 with Dr. Hoffman on the “Purification of Gallium by Fractional Crystallization”. Hoffman is recalled as the senior member of another father-son pair among several at the Bureau. 

Dr. Hoffman attained a high-purity gallium and prepared a beautiful pyramidal crystal. The crystal was presented to Frederick Bates whose Polarimetry Section had supported the research. Highest purity gallium was required for use as an alloying element in the cadmium-vapor arc lamp used in polarimetry. Mr. Bates placed the crystal on his desk in the West Building for all to admire. As the afternoon wore on, light from the sun crept across the desk and the crystal melted, the melting point of gallium being 29.78 C (85.6 F). Mr. Bates was chagrined to report the demise of the crystal but fortunately a photograph survived in a paper in 1934 by Hoffman on “Purification of Gallium”. 

Spectrographic analysis was applied in other areas where the purity of the materials was critical for Bureau measurements. Typically the research involved several laboratories across Division lines; for example, in 1934 W. F. Roeser and H. T. Wensel of the Heat and Power Division published a paper on the “Freezing Point of Rhodium”. The metal used was purified by Edward Wichers of the Chemistry Division and its purity was determined spectrographically by our laboratory, a part of the Optics Division. 

Quantitative spectrographic methods were developed in our laboratory, one being the analysis of tin for impurities. The Bureau had been assigned the task of testing representative samples of fusible tin safety plugs to assure their proper operation in protecting steam boilers from explosion. Under the severe conditions of boiler service, certain impurities tended to form networks which held the melting tin from blowing out of its tubular holder even at dangerously high temperatures. 

The method that was developed was published in 1942 as the “Spark Spectrographic Analysis of Commercial Tin’. It provided a considerable gain in speed of analysis. The time of analysis for a group of six tin samples, with 10 elements determined in each, was two hours for the spectrographic method compared to two days for the wet chemical methods that it replaced.