Henry, William

(1774–1836) British chemist: discovered law of gas solubility.

Henry was the third and most successful son of Thomas Henry, whose profitable ventures in chemistry had included the early use of chlorine for bleaching textiles, the preparation and use of bleaching powder (Cl2 absorbed in lime) as a useful alternative to the gas, and the making of ‘calcined magnesia’ (ie Mg(OH)2 ) for medicinal use. Young William was injured by a falling beam at the age of 10; the injuries gave him ill health and pain throughout his life, and he finally killed himself. He qualified in medicine in 1807 but his research was mainly in chemistry. He is now best known for Henry’s Law, which states that the mass of a gas dissolved by a given volume of a solvent, at a constant temperature, is directly proportional to the pressure of gas with which the solvent is in equilibrium. The law holds well only for slightly soluble gases at low pressures.

Henry was a close friend of but, despite superior skill and range as an experimenter, lacked his friend’s boldness as a theorist and never committed himself to the atomic theory whose birth he had assisted.