Andrews, Thomas (1813-1885)

Irish physical chemist, best known for postulating the idea of critical temperature and pressure from his experimental work on the liquefaction of gases, which demonstrated the continuity of the liquid and gaseous states. He also studied heats of chemical combination and was the first to establish the composition of ozone, proving it to be an allotrope (see allotropy) of oxygen. Andrews was born in Belfast and attended five universities, beginning at the age of 15. In 1835 he graduated from Edinburgh as a qualified doctor and surgeon. He was professor of chemistry at Queen's College, Belfast, 1849-79. Studying chemical combination, Andrews succeeded in the direct determination of heats of neutralization and of formation of halides (chlorides, bromides, and iodides). Many other scientists had tried to explain the relationship between gases and liquids. Andrews constructed elaborate equipment in which he initially investigated the liquefaction of carbon dioxide, and by 1869 he had concluded that it has a critical temperature (or critical point) of 30.9°C/87.6°F, above which it cannot be condensed into a liquid by any pressure.