William Prout

William Prout (January 15, 1785 – April 9, 1850) was an English chemist and physician best known. His life was spent as a practising physician in London, but he also occupied himself with chemical research. He was an active worker in biological chemistry and carried out many analyses of the secretions of living organisms, which he believed were produced by the breakdown of bodily tissues. In 1823, he discovered that stomach juices contain hydrochloric acid, which can be separated from gastric juice by distillation. In 1827, he proposed the classification of substances in food into carbohydrates, fats, and proteins.

He is better remembered, however, for his researches into physical chemistry. In 1815, based on the tables of atomic weights available at the time, he hypothesized that the atomic weight of every element is an integer multiple of that of hydrogen, suggesting that the hydrogen atom is the only truly fundamental particle, and that the atoms of the other elements are made of groupings of various numbers of hydrogen atoms. While Prout's hypothesis was not borne out by later more accurate measurements of the atomic weights, it was a sufficiently fundamental insight into the structure of the atom that in 1920, Ernest Rutherford chose the name of the newly-discovered proton to, among other reasons, give credit to Prout.

Prout contributed to the improvement of the barometer, and the Royal Society of London adopted his design as a national standard.