Brønsted, Johannes Nicolaus

20th Century
Born: Varde, Jutland (Denmark), 22 February 1879 
Died: Copenhagen (Denmark), 17 December 1947 
Brønsted studied in Copenhagen at the Polytechnic Institute and University, obtained his doctorate in 1908 and was appointed the same year to a newly established professorship in chemistry with teaching courses at both universities. The double duties ended in 1930 when he was given a single professorship with the institute of physical chemistry at the University. Brønsted’s main achievement was the development of a valid concept of acids and bases in 1923, often referred to as the Brønsted theory of acids and bases. In Brønsted’s concept, every acid is related to a conjugate base and vice versa. The definition applies to all solvents and not just to water. He also studied activity coefficients introduced by G.N. Lewis and, together with the later Nobel laureate G. Hevesy, the separation of isotopes by molecular distillation. Since 1927 Brønsted became increasingly interested in catalytic effects of acids and bases.