BY ROBERT A. ALBERTY
THE FOCUS OF Lewis Longsworth's scientific research was the measurement of mobilities of ions and molecules in liquid media. Initially, he studied small ions under the influence of an electric field by the moving boundary method, and then he extended his research to the study of proteins and nucleic acids and then complexes. He made major contributions to the analysis of mixtures of proteins by electrophoresis.
Later in his career Longsworth studied the diffusion of neutral molecules in solution, where the gradient of the chemical potential provides the driving force. Diffusion affords a means for the study of the mobility of a nonelectrolyte in any medium in which it is soluble. He provided an early model of separation methods in laboratories to obtain purified biological substances. His experimental work was characterized by great care, high precision, and innovation of new experimental methods.
Longsworth spent his whole career at the Rockefeller Institute, where MacInnes, Shedlovsky, and Longsworth created one of the world's outstanding centers of electrolyte research and brought it to bear on biological problems.