Irving M. Klotz, PhD, deceased, was a noted expert in chemical thermodynamics and the physical chemistry of proteins. Dr. Klotz was elected to the American Academy of Arts & Sciences in 1968 and the National Academy of Sciences in 1970. He joined the Northwestern faculty in 1940 and retired in 1986. Dr. Klotz was named a Fellow of the Royal Society of Medicine in 1971 and published more than 200 scientific articles in peer-reviewed journals. He wrote Chemical Thermodynamics: Basic Theory and Methods in 1950. Dr. Rosenberg began working with him as coauthor with the third edition. Robert M. Rosenberg, PhD, is Emeritus Professor of Chemistry at Lawrence University and an Adjunct Professor of Chemistry at Northwestern University.