Belgian-born American chemist whose studies of acetylene culminated in the discovery of lewisite, a chemical-warfare agent, and neoprene, the first commercially successful synthetic rubber.

Nieuwland, emigrating with his parents to the United States in 1880, graduated in 1899 from the University of Notre Dame, Ind. Ordained a Roman Catholic priest in 1903, he studied botany and chemistry at the Catholic University of America, Washington, D.C., receiving a Ph.D. in 1904. Returning to Notre Dame, he was professor of botany from 1904 to 1918 and professor of organic chemistry from 1918 to 1936. His doctoral research concerned the chemistry of acetylene, a lifelong interest. Early in his studies he discovered dichloro(2-chlorovinyl)arsine, but, because of its highly poisonous properties, he suspended all research on it. Later known as lewisite, this compound was developed as a chemical weapon but was never used.

In 1920 Nieuwland discovered that acetylene could be polymerized (its molecules combined to form giant molecules) to produce divinylacetylene, a substance similar to rubber. Eleven years later, a group of chemists working under Wallace H. Carothers at E.I. du Pont de Nemours & Company succeeded in modifying Nieuwland's polymerization procedure to produce neoprene.