Robert Boyle

I

INTRODUCTION

Robert Boyle (1627-1691), English natural philosopher and one of the founders of modern chemistry. Boyle is best remembered for Boyle’s law, a physical law that explains how the pressure and volume of a gas are related. He was instrumental in the founding of the Royal Society, a British organization dedicated to the advancement of the sciences. Boyle was also a pioneer in the use of experiments and the scientific method to test his theories.

II

BOYLE’S LIFE

Boyle was born in Lismore Castle in Lismore, Ireland. His father was Richard Boyle, who was the first earl of Cork. Robert learned to speak French and Latin as a child and went to Eton College in England at the early age of eight.

In 1641 Boyle began a tour of Europe, returning to England in 1644. He settled there, because Ireland was in turmoil over colonization efforts by English protestants. Boyle had inherited parts of several estates upon his father’s death in 1643, and income from these allowed him to live independently. He joined a group known as the Invisible College, whose aim was to cultivate ideas called the “new philosophy.” The new philosophy included new methods of experimental science, in which scientists sought to prove or disprove hypotheses through careful experiments. Boyle moved to Oxford, which was one of the meeting places of the Invisible College, in 1654. King Charles II granted a charter in 1663 that allowed the Invisible College to become 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 and lived with his sister until his death in 1691.

III

BOYLE’S WORK

Boyle carried out his most active research while he lived in Oxford. Much of his research dealt with the behavior of gases, including the earth’s atmosphere. By careful experiments, he established Boyle’s law. Boyle’s law states that the volume of a given amount of gas varies inversely with its pressure, if temperature is constant. This means that at a constant temperature, the pressure of a gas will increase as the volume of the gas is decreased, and vice versa. Boyle determined the density of air in the earth’s atmosphere and pointed out that the weight of objects varies with changes in atmospheric pressure. He compared the lower layers of the earth’s atmosphere to a number of sponges or small springs that the weight of the layers above compresses. In 1660 Boyle published these findings in a book entitled The Spring of Air.

A year later Boyle published The Sceptical Chymist, in which he criticized previous researchers for believing that salt, sulfur, and mercury were the “true principles of things.” He advanced the view that the basic elements of matter are “corpuscles,” or particles, of various sorts and sizes. Boyle believed that these corpuscles were capable of arranging themselves into groups, and that each group constituted a chemical substance. He successfully distinguished between mixtures (substances mixed together) and compounds (chemically bonded substances) and showed that a compound can have very different qualities from those of its constituents.

Boyle studied the chemistry of combustion around 1660 with the assistance of his pupil Robert Hooke. They pumped the air out of a jar and showed that neither charcoal nor sulfur burns in a vacuum, although both substances burn in the presence of air. Boyle then found that a mixture of either substance with saltpeter (potassium nitrate) catches fire even when in a vacuum and concluded that combustion must depend on something common to both air and saltpeter. The component of air and saltpeter that allows combustion was not isolated until British chemist Joseph Priestley did so in 1774. This substance was not given its present name until French chemist Antoine Lavoisier named it oxygen three years later.

Boyle also coined the term analysis and used many of the reactions that modern qualitative chemists use today. He introduced certain plant extracts, notably litmus, which indicates whether a substance is an acid or a base (see Acids and Bases). In 1667 he was the first to study the phenomenon of bioluminescence, the emission of light from living organisms. He showed that fungi and bacteria require air (oxygen) for luminescence, becoming dark in a vacuum and glowing again when air is readmitted. Boyle drew a comparison between a glowing coal and phosphorescent wood, although oxygen was still not known and combustion was not properly understood. Boyle also seems to have been the first to construct a small, portable, box-type camera obscura in about 1665. A camera obscura is a system used to project an image onto a surface. Boyle’s camera obscura 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. Hydrometers consist of a sealed capsule of lead or mercury inside a glass tube into which the liquid being measured is placed. The height at which the capsule floats represents the density of the liquid. Boyle is also credited with the invention of the match. In 1680 he found that he could produce fire by drawing a sulfur-tipped splint through a fold in a piece of paper that was coated with phosphorus. Boyle experimented in animal physiology, although he disliked performing actual dissections. He also carried out experiments in the hope of changing one metal into another.

Boyle was interested in theology as well as science. He spent large sums on biblical translations and learned Hebrew, Greek, and Syriac in order to further his studies of the Scriptures. He founded the Boyle Lectures for defending Christianity against other religions.

Boyle accomplished much important work in physics. He studied the behavior of gases, the role of air in allowing sound to travel, and the outward force of water in the process of freezing. He was also interested in the ability of crystals to bend light, the density of liquids, electricity, color, and the behavior of liquids at rest, among other physical topics. Boyle’s greatest fondness was researching in chemistry. He was the main agent in changing the unscientific field of alchemy, which was mostly concerned with turning common metals into precious metals, into modern scientific chemistry. He was the first person to work toward removing the mystique around chemistry and to change it into a pure science. He questioned the basis of the chemical theory of his day and taught that chemistry’s purpose was to determine the compositions of substances. After his death, his natural history collections passed as a bequest to the Royal Society.