 In 1906 he published the first of his many papers on electron affinity, and, simultaneously with the English chemist Thomas Martin Lowry, he introduced the protonic theory of acid-base reactions in 1923.That same year, Gilbert N. Lewis proposed an electronic theory of acid-base reactions, but both theories remain commonly used.In World War II, Brønsted's opposition to the Nazis led to his election to the Danish parliament in 1947, but he was too ill to take his seat and died shortly after the election.