The Brønsted- Lowry theory of acids

Arrhenius's ideas moved our understanding of acids and bases forward a long way, but there was one major problem with the ideas. They depended on all acid/base reactions taking place in solution in water - which course they don't. The reaction between hydrochloric acid and ammonia gas is a very good example of a neutralisation reaction which does not take place in water. In 1923 two different scientists, working quite independently, came up with an identical explanation for the behaviour of acids and bases Named after Johannes Nicolaus Brønsted (1879 - 1947) and Thomas Martin Lowry (1874 - 1936), the Brønsted-Lowry theory describes acids and bases in terms of the transfer of a proton from the acid to the base. They simply defined an acid as any ion or molecule able to produce a proton, while a base is any ion or molecule able to take up a proton. Their ideas did not conflict with what Arrhenius had said, but they took the model further forward. The Brønsted-Lowry theory explained reactions which Arrhenius's model could not. The new model was rapidly accepted and used by scientists - Brønsted and Lowry did not have the long wait for acceptance that Arrhenius had had to put up with.

Thomas Martin Lowry was the son of a Wesleyan army chaplain from Bradford in England. He was educated at the Central Technical College (which later became part of Imperial College), London, where from 1896 to 1913 he served as assistant to Henry Armstrong. From 1904 he was also head of chemistry at Westminster Training College until he moved to Guy's Hospital, London, in 1913 to become head of the Chemistry Department. In 1920 he was appointed as the first professor of physical chemistry at Cambridge University.

The son of a civil engineer, Johannes Nicolaus Brønsted was born on February 22nd, 1879 in Varde, a small town in West Jutland. His mother died soon after his birth, and his father remarried. However, when Johannes was only 14 years old his father died as well and he had to leave the farm where he had been brought up. Brønsted and his sister moved to Copenhagen with their stepmother and he attended the 'Metropolitanskolen' for three years . He passed his 'studentereksamen' (University entrance examination) in the summer of 1897.In the autumn of 1897 Brønsted took up studies at the (old) Polytecnic Institute in the street Sølvgade in Copenhagen. He completed his first degree studies in engineering in 1899, and began studies in pure science at Copenhagen University. He took his 'magister' degree in Chemistry in 1902.

At the Polytecnic Institute Brønsted met Charlotte Louise Warberg, who in 1902 became one of the very first female engineers in Denmark. They were married in 1903 and moved into a flat at Forchhammersvej in Copenhagen, and went on to have several children. There was no academic position immediately available for Brønsted in 1902 and it was three years before he could return to the University Chemical Laboratories to take up a position as an assistant. However, he was obviously very talented and from 17 December 1908 he was made professor.

In 1923, within several months of each other, Johannes Nicolaus Brønsted (Denmark) and Thomas Martin Lowry (England) published essentially the same theory about how acids and bases behave. Since they came to their conclusions independently of each other, both names have been used for the in naming the theory.

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Lewis acids

Svante Arrhenius