Boyle, Robert, 1627-1691
Irish natural philosopher and one of the founders of modern chemistry. He is best remembered for the law named after him, which states that, at a constant temperature, the volume of a given mass of gas is inversely proportional to the pressure upon it. He was instrumental in the founding of the Royal Society and a pioneer in the use of experiment and the scientific method.
Boyle was born on 25 January 1627 in Lismore Castle, County Waterford, the fourteenth child and seventh son of the Earl of Cork. He learned to speak French and Latin as a child and was sent to Eton College at the early age of eight. In 1641 he visited Italy, returning to England in 1644. He joined a group known as the Invisible College, whose aim was to cultivate the ‘new philosophy’ and which met at Gresham College, London, and in Oxford, where Boyle went to live in 1654. The Invisible College became, under a charter granted by Charles II in 1663, the Royal Society of London for Improving Natural Knowledge, and Boyle was a member of its first council. (He was elected president of the Royal Society in 1680, but declined the office.) He moved to London in 1668 where he lived with his sister for the rest of his life. He died there on 30 December 1691.
Boyle's most active research was carried out while he lived in Oxford. By careful experiments he established the law that now bears his name. He determined the density of air and pointed out that bodies alter in weight according to the varying buoyancy of the atmosphere. He compared the lower strata of the air to a number of sponges or small springs that are compressed by the weight of the layers of air above them. In 1660 these findings were published in a book The Spring of Air, which also gave us the word ‘elastic’ in its present meaning(Boyle's law is not stated clearly until the revised edition was published in 1662).
A year later Boyle published The Sceptical Chymist, in which he criticized previous researchers for thinking that salt, sulphur, and mercury were the ‘true principles of things’. He advanced towards the view that matter is ultimately composed of ‘corpuscles’ of various sorts and sizes, capable of arranging themselves into groups, and that each group constitutes a chemical substance. He successfully distinguished between mixtures and compounds and showed that a compound can have very different qualities from those of its constituents.
Also in about 1660 Boyle studied the chemistry of combustion, with the assistance of his pupil Robert Hooke. They proved, using an air pump, that neither charcoal nor sulphur burns when strongly heated in a vessel exhausted of air, although each inflames as soon as air is re-admitted. Boyle then found that a mixture of either substance with saltpetre (potassium nitrate) catches fire even when heated in a vacuum and concluded that combustion must depend on something common to both air and saltpetre. Further experiments involved burning a range of combustible substances in a bell jar of air enclosed over water. But it was left to Joseph Priestley in 1774 to discover the component of air that vigorously supports combustion, which three years later Antoine Lavoisier named ‘oxygen’.
The term ‘analysis’ was coined by Boyle and many of the reactions still used in qualitative work were known to him. He also introduced certain plant extracts, notably litmus, for the indication of acids and bases. In 1667 he was the first to study the phenomenon of bioluminescence, when he showed that fungi and bacteria require air (oxygen) for luminescence, becoming dark in a vacuum and luminescing again when air is re-admitted. In this he drew a comparison between a glowing coal and phosphorescent wood, although oxygen was still not known and combustion not properly understood. Boyle also seems to have been the first to construct a small portable box-type camera obscura in about 1665. It could be extended or shortened like a telescope to focus an image on a piece of paper stretched across the back of the box opposite the lens.
In 1665 Boyle published the first account in England of the use of a hydrometer for measuring the density of liquids. The instrument he described is essentially the same as those in use today. He can also be credited with the invention of the first match. In 1680 he found that by coating coarse paper with phosphorus, fire was produced when a sulphur-tipped splint was drawn through a fold in the treated paper. Boyle experimented in physiology, although ‘the tenderness of his nature’ prevented him from performing actual dissections. He also carried out experiments in the hope of changing one metal into another, and was instrumental in obtaining in 1689 the repeal of the statute of Henry IV against multiplying gold and silver.
Besides being a busy natural philosopher, Boyle was interested in theology and in 1665 would have received the provostship of Eton had he taken orders. He learned Hebrew, Greek, and Syriac in order to further his studies of the scriptures, and spent large sums on biblical translations.
Boyle accomplished much important work in physics, with Boyle's law, the role of air in propagating sound, the expansive force of freezing water, the refractive powers of crystals, the density of liquids, electricity, colour, hydrostatics and so on. But his greatest fondness was researching in chemistry, and he was the main agent in changing the outlook from an alchemical to a chemical one. He was the first to work towards removing the mystique and making chemistry into a pure science. He questioned the basis of the chemical theory of his day and taught that the proper object of chemistry was to determine the compositions of substances. His great merit as a scientific investigator was that he carried out the principles of Francis Bacon, although he did not consider himself to be a follower of him or of any other teacher. After his death, his natural history collections were passed as a bequest to the Royal Society.