His early studies of molecular kinetics led to the publication of "Thermodynamics for Students of Chemistry" and "The Kinetics of Chemical Change" in 1926. With Harold Warris Thompson he studied the explosive reaction of hydrogen and oxygen and described the phenomenon of chain reaction. His subsequent work on chemical changes in the bacterial cell proved to be of great importance in later research work on antibiotics and therapeutic agents, and his book, "The Chemical Kinetics of the Bacterial Cell" was published in 1946, followed by "Growth, Function and Regulation in Bacterial Cells" in 1966. In 1951 he published "The Structure of Physical Chemistry". It was republished as an Oxford Classic Texts in the Physical Sciences by Oxford University Press in 2005.