In 1929 , a year before graduating , he was appointed a Junior Scientific Aid to the U.S. Department of Agriculture .
In 1929 , a year before graduating , he was worked as a chemist in the fertilizer section of the Bureau of Chemistry and Soils .
In 1929 , a year before graduating , he was appointed a Junior Scientific Aid to the U.S. Department of Agriculture , and worked as a chemist in the fertilizer section of the Bureau of Chemistry and Soils .