Thomas Andrews (19.12.1813-26.02.1885) was an Irish physical chemist and a Fellow of the Royal Society (1849). He was born in Belfast. He studied chemistry in Glasgow and Paris and medicine in Dublin and Belfast, and in 1835 received the degree of Doctor of Medicine at Edinburgh. He had a medical practice in Belfast, then became the first professor of chemistry at the Academical Institution, and in 1849 — 79 was professor at the Royal College (Belfast).
His work concerned chiefly the study of the critical state of matter. He discovered the continuity of the gaseous and liquid states of matter and gave a theory of it, introducing the concept of the critical point. Independently of others he discovered critical phenomena in the “liquid — vapour” equilibrium in solutions and introduced the concepts of critical temperature and critical pressure (in 1861 he detected the critical temperature of carbon dioxide). He studied the liquefaction of gases. Andrews's research had a great influence on the development of the theory of the equation of state and of phase equilibrium.
He was a Fellow of the Royal Society of Edinburgh.