Henry, William (1774–1836)

English chemist and physician. In 1803 he formulated Henry's law, which states that when a gas is dissolved in a liquid at a given temperature, the mass that dissolves is in direct proportion to the pressure of the gas.

Henry was born in Manchester and graduated from Edinburgh. In poor health after a childhood accident, he worked mainly for his father, an industrial chemist.

Henry worked for about 20 years on the analysis of inflammable mixtures of gases and attempted to find correlations between chemical composition and illuminative properties. He established that firedamp – the cause of many mining disasters – is methane, and confirmed the composition of methane and ethane. Like English chemist John Dalton, Henry showed that hydrogen and carbon combine in definite proportions to form a limited number of compounds.

In medicine, Henry studied contagious diseases. He believed that these were spread by chemicals which could be rendered harmless by heating; he used heat to disinfect clothing during an outbreak of cholera in 1831.

A series of chemistry lectures which he gave 1798–99 were later published as Elements of Experimental Chemistry and became a highly successful textbook.