As a part of the Manhattan Project, Mallinckrodt developed a crude method of uranium purification using ether as a coolant. African pitchblende, which contained high concentrations of uranium, made up much of the crude ore the company then processed. The combination of extremely radioactive materials, wartime haste and lack of experience led to over-exposures among uranium workers here. Due to wartime secrecy, the workers weren’t given a clear indication of the dangers.