What aspect of coal did Rosalind Franklin research?

Rosalind Franklin researched the structure and porosity of coal. Before her famous DNA work, she studied coal’s physical chemistry at the British Coal Utilisation Research Association, where she began working in 1942.

Franklin used techniques involving gases such as helium to measure coal’s density and examine its microscopic pores. Different gases produced different measurements because coal contains networks of tiny openings and constrictions that allow some molecules to enter more easily than others. This showed that coal’s pore structure was complex and could act like a molecular sieve.

Her findings had practical importance during the Second World War. Understanding coal’s porosity helped scientists classify different coals and predict how they would behave as fuels or as materials for absorbing gases in devices such as gas masks. The research formed the basis of Franklin’s doctoral thesis, which Cambridge awarded in 1945. It also foreshadowed the detailed structural analysis that later defined her work on DNA and viruses.