a solid nickel diffuser. The SAM Laboratories had already attempted this and failed. Heussner experimented with a prototype in a building built within a building, and found that it could be done, so long as the series of pickling and scaling steps required were done without anything coming in contact with oxygen. Chrysler's entire factory at Lynch Road in Detroit was turned over to the manufacture of diffusers. The electroplating process required over of floor space, several thousand workers and a complicated air filtration system to ensure the nickel was not contaminated. By the war's end, Chrysler had built and shipped more than 3,500 diffusers. Pumps The gaseous diffusion process required suitable pumps that had to meet stringent requirements. Like the diffusers, they had to resist corrosion from the uranium hexafluoride feed. Corrosion would not only damage the pumps, it would contaminate the feed. They could not afford any leakage of uranium hexafluoride, especially if it was already enriched, or of oil, which would react with the uranium hexafluoride. They had to pump at high rates, and handle a gas twelve times as dense as air. To meet these requirements, the SAM Laboratories chose to use centrifugal pumps. They were aware that the desired compression ratio of 2.3:1 to 3.2:1 was unusually high for this type of pump. For some purposes, a reciprocating pump would suffice, and these were designed by Boorse at the SAM Laboratories, while Ingersoll Rand tackled the centrifugal pumps. In early 1943, Ingersoll Rand pulled out. Keith approached the Clark Compressor Company and Worthington Pump and Machinery but they turned it down, saying it could not be done. So Keith and Groves saw executives at Allis-Chalmers, who agreed to build a new factory to produce the pumps, even though the pump design was still uncertain. The SAM Laboratories came up with a design, and Westinghouse built some prototypes that were successfully tested. Then Judson Swearingen at the Elliott Company came up with a revolutionary and promising design that was mechanically stable with seals that would contain the gas. This design was manufactured by Allis-Chalmers. Barriers Difficulties with the diffusers and pumps paled into insignificance besides those with the porous barrier. To work, the gaseous diffusion process required a barrier with microscopic holes, but not subject to plugging. It had to be extremely porous, but strong enough to handle the high pressures. And, like everything else, it