Chemistry: 1915

Richards, Theodore William (1868-1928), an American chemist, won the Nobel Prize in chemistry in 1914 for determining the relative atomic masses of many elements. An element's relative atomic mass equals its mass divided by (1/12) of the mass of carbon 12, the most abundant form of carbon. An older term for relative atomic mass is atomic weight. He was the first American chemist to be awarded the prize.

Much of Richards's research focused on relative atomic masses. He improved the accuracy of methods to weigh atoms-that is, to measure their mass. He and his students accurately measured the relative atomic masses of 55 elements. He also developed a theory that some atoms were compressible. He proved the existence of lead isotopes (forms of the element with different relative atomic masses) by investigating the weight of lead from different sources.

Richards invented the nephelometer, a device that uses light dispersion to measure the concentration of suspended matter in a liquid. His other work included research in thermochemistry, the study of heat and chemical reactions, and in electrochemistry, the study of the relationships between electricity and chemistry.

Richards was born in Germantown, Pennsylvania, on Jan. 31, 1868. He studied and taught at Harvard University in Cambridge, Massachusetts. He died on April 2, 1928.