Robert Boyle (1627-1691), Anglo-Irish chemist. Boyle established chemistry as a separate science and stressed the need for experimental precision and accurate observation. He rejected the theory that four elements (fire, air, water and earth) were the basic constituents of the Universe, instead postulating the existence of a range of chemical elements. He carried out a wide range of experiments on gases (his 1659 air pump is at lower right) and Boyle's Law on gases is named for him. He devised analytical tests: vegetable dyes as acid-base indicators, and flame tests for metals. 'The Skeptical Chymist' (1661) was his major work.