Enrico Fermi was proposing to build. The only uranium metal available commercially was produced by the Westinghouse Electric and Manufacturing Company, using a photochemical process that produced ingots the size of a quarter that were sold for around $20 per gram. Edward Creutz, the head of the group responsible for fabricating the uranium, wanted a metal sphere the size of an orange for his experiments. With Westinghouse's process, it would have cost $200,000 and taken a year to produce. The other major problem was the purity of the uranium. Impurities could act as neutron poisons and prevent a nuclear reactor from working, but the uranium oxide that Fermi wanted for his experimental reactor contained unacceptably large amounts of impurities. As a result, references published before 1942 typically listed its melting point at around when pure uranium metal actually melts at . The most effective way to purify uranium oxide in the laboratory was to take advantage of the fact that uranium nitrate is soluble in ether. Scaling this process up for industrial production was a dangerous proposition; ether was explosive, and a factory using large quantities was likely to blow up or burn down. Compton and Spedding turned to Mallinckrodt in Saint Louis, Missouri, which had experience with ether. Spedding went over the details with Mallinckrodt's chemical engineers, Henry V. Farr and John R. Ruhoff, on 17 April 1942. Within a few months, sixty tons of highly pure uranium oxide was produced. Spedding recruited two chemistry professors at Ames for his group there, Harley Wilhelm and I. B. Johns. Spedding and Wilhelm began looking for ways to create the uranium metal. At the time, it was produced in the form of a powder, and was highly pyrophoric. It could be pressed and sintered and stored in cans, but to be useful, it needed to be melted and cast. The Ames team found that molten uranium could be cast in a graphite container. Although graphite was known to react with uranium, this could be managed because the carbide formed only where the two touched. To produce uranium metal, they tried reducing uranium oxide with hydrogen, but this did not work. They then investigated a process (now known as the Ames process) originally developed by J. C. Goggins and others at the University of New Hampshire in 1926. This involved mixing uranium tetrachloride and calcium metal in a calcium oxide-lined steel pressure