Skarstrom’s separator

As the plot of the Covid-19 pandemic continues to play out, it can be easy to forget the real horror of this disease. The sight of patients gasping for breath is chilling, and many have needed an additional oxygen supply. Producing this oxygen has been a key challenge of the pandemic, but one made easier by a technique developed in the 1950s by a man who specialised in separation.

Charles Skarstrom was born in 1906, the son of a leading professor of physical education. In 1924 he started a physics degree at his father’s old university, Columbia, in New York, US. He left in 1933 with a master’s degree to join Jesse Beams at the University of Virginia. Beams had begun to test a hypothesis made by Frederick Lindemann and Francis Aston that a centrifuge might be a means to separate isotopes in gases or vapours. Skarstrom joined the group just as difficult and dangerous work on enrichment in the heavier chlorine isotopomers of carbon tetrachloride was being prepared for publication. For his PhD thesis, submitted in 1939, Skarstrom scaled up the method.

As part of the Manhattan project to build the atomic bomb, Beams proposed using his gas ultracentrifuges to separate the fissile uranium-235 from the rest. Several patents under Skarstrom’s name, filed long after the end of the war, describe seals and bearings related to this project. However, Beams and his team were unable to develop a system robust enough to do the job, and the isotopes used in the weapons dropped on Hiroshima and Nagasaki in Japan were separated by more conventional gas diffusion through porous membranes.