In January 1942, Szilard joined the Metallurgical Laboratory in Chicago as a research associate, and later the chief physicist. Alvin Weinberg noted that Szilard served as the project "gadfly", asking all the embarrassing questions. Szilard provided important insights. While uranium-238 did not fission readily with slow, moderated neutrons, it might still fission with the fast neutrons produced by fission. This effect was small but crucial. Szilard made suggestions that improved the uranium canning process, and worked with David Gurinsky and Ed Creutz on a method for recovering uranium from its salts.