Boyle , Robert

(1627–1691) British chemist and physicist

The son of the Earl of Cork, and born at Lismore Castle, now in the Republic of Ireland, Boyle was a member of an aristocratic and wealthy family. He spent four years at Eton College and from 1638 studied at Geneva, returning to London in 1644. He then retired to his estate at Stalbridge, Dorset, where he took up the life of a scientific ‘virtuoso’.

In 1654 Boyle moved to Oxford, where he worked on pneumatics. In 1658–59 he had an air pump built for him by Robert Hooke, after the type invented by Otto von Guericke in 1654. Boyle was ably assisted by Hooke in various pioneering experiments in which he showed that air was essential for the transmission of sound, and for respiration and combustion – and that the last two processes exhausted only part of the air.

In Boyle's most famous experiment he took a U-shaped tube with a shorter closed end, and a longer open end into which he poured mercury, thus isolating a given volume of air in the shorter end. When the mercury was level in both ‘limbs’ the air was under atmospheric pressure, and by adding more mercury to the longer limb the pressure could be increased. Boyle found that the volume was halved if the pressure was doubled, reduced to a third if the pressure was tripled, and so on – and that this process was reversible. Boyle's work on the compressibility of air was published in New Experiments Physico-Mechanicall, Touching the Spring of the Air and its Effects (1660) but the famous law stating that the pressure and volume of air are inversely proportional was not stated explicitly until the second edition (1662). The law, known as Boyle's law in America and Britain but in Europe as Mariotte's law, can be expressed (where C is a constant) as p×V =C; that is, the product of the pressure and volume of a gas remains constant if, as Edmé Mariotte noted, the temperature remains constant. This law (together with its companion gas law, that of Jacques Charles) is true only for ideal gases, but approximately holds for real gases at very low pressures and at high temperatures.

Boyle developed a mechanical corpuscular philosophy of his own, derived from the Greek tradition and the work of Galileo and Pierre Gassendi. In Boyle's conception all physical phenomena could be explained by corpuscules of different shapes, sizes, and motions, this corpuscular matter being capable of infinite transformations (which allowed the possibility of alchemy and excluded the existence of elements).

However, in The Sceptical Chymist (1661) Boyle proposed a view of matter that presaged modern views and certainly disposed effectively of the Aristotelian doctrine of the four elements. He supposed that all matter was composed of primary particles, some of which joined together to form semi-indivisible corpuscles and whose organization and motion explained all qualities of matter.

Boyle's main contribution to chemistry was his insistence on experiment, precision, and accurate observation. He devised many analytical tests including the use of vegetable dyes as acid–base indicators and of flame tests to detect metals. The chemist's concern for the purity of his materials began with Boyle. Although he prepared hydrogen by the action of acids on iron and observed the oxidation of mercury and its subsequent regeneration on further heating, the ‘fixation’ of gases in bodies remained unexplained in his work. Likewise, he observed the increase in weight of metals on calcination but attributed this to heat, which he sometimes regarded as material.

Boyle left Oxford for London in 1668 where, despite his scholarly nature and poor health, he was very much at the center of scientific life as a founder member of the Royal Society. He believed, like his hero Francis Bacon, that science could be put to practical use.