acceptable, and a cost-plus-fixed-fee contract was negotiated with a fee of $216,000 for services up to the end of June 1945. The contract was terminated early on 1May 1945, when Union Carbide took over the plant. Ford, Bacon & Davis was therefore paid $202,000. The other exception was the fluorine plant. Hooker Chemical was asked to supervise its construction of the fluorine plant, and initially to operate it for a fixed fee of $24,500. The plant was turned over to Union Carbide on 1February 1945. Part of the K-300 complex was taken over by Union Carbide in August 1944, and was run as a pilot plant, training operators and developing procedures, using nitrogen instead of uranium hexafluoride until October 1944, and then perfluoroheptane until April 1945. The design of the gaseous diffusion plant allowed for it to be completed in sections, and for these to be put into operation while work continued on the others. J. A. Jones completed the first 60 stages by the end of 1944. Before each stage was accepted, it underwent tests by J. A. Jones, Carbide and Carbon and SAM Laboratories technicians to verify that the equipment was working and there were no leaks. Between four and six hundred people devoted eight months to this testing. Perfluoroheptane was used as a test fluid until February 1945, when it was decided to use uranium hexafluoride despite its corrosive nature. The Manhattan District engineer, Colonel Kenneth Nichols, placed Major John J. Moran in charge of production at K-25. Production commenced in February 1945, and the first product was shipped to the calutrons in March. By April, the gaseous diffusion plant was producing 1.1 percent product. It was then decided that instead of processing uranium hexafluoride feed from the Harshaw Chemical Company, the gaseous diffusion plant would take the product of the S-50 thermal diffusion plant, with an average enrichment of about 0.85 percent. Product enrichment continued to improve, as more stages came online and performed better than anticipated. In June product was being enriched to 7percent; by September it was 23 percent. The S-50 plant ceased operation on 9September, and Kellex transferred the last unit to Union Carbide on 11 September 1945. Highly enriched uranium was used in the Little Boy atomic bomb used in the bombing of Hiroshima on 6August 1945. With the end of the war in August 1945, the Manhattan Project's priority shifted from