This remarkable century saw the science of chemistry evolve from the experiments and vagaries of alchemy. Industry had long been accumulating chemical knowledge through such operations as smelting iron, tanning leather, mixing dyes, brewing beer; but the investigation of substances in their composition, combination, and transformation had been for the most part left to alchemists seeking gold, or to pharmacologists concocting drugs, or to philosophers, from Democritus to Descartes, puzzling over the constitution of matter. Some approach to chemistry had been made by Andreas Libavius in 1597 and by Jan van Helmont in 1640; but both of these men shared the alchemist’s hope of transmuting “base” metal into gold. Boyle himself made experiments with this aim. In 1689 he secured repeal of an old English statute against “multiplying gold and silver,” 43 and at his death (1691) he left to his executors a quantity of red earth with instructions for trying to turn it into gold. 44 Now that the transmutation of metals is a cliché of chemistry we can applaud the science in alchemy while condemning and concealing the itch for gold.

The greatest blow to alchemy was the publication of Boyle’s Sceptical Chymist (1661)—the prime classic in the history of chemistry. He apologized for “suffering” his treatise “to pass abroad so maimed and imperfect,” 45 but, with his many ailments, he was never confident of much longer life. He was consoled to “observe that of late chymistry begins, as indeed it deserves, to be cultivated by learned men who before despised it.” 46 He called his chemistry skeptical because he proposed to reject all mystical explanations and occult qualities as the “sanctuary of ignorance,” and was resolved to rely upon “experiments rather than syllogisms.” 47 He abandoned the traditional division of matter into the four elements of air, fire, water, and earth; these, he argued, were compounds, not elements; the real elements were rather “certain primitive and simple, or perfectly unmingled bodies, which, not being made of any other bodies or of one another,” are the ingredients of all compounds, and into which all compounds may be resolved. He did not mean that the elements were the ultimate constituents of matter; these minima naturalia, he thought, were tiny particles, invisible to the eye, and differing in shape and size, like the atoms of Leucippus. From the diversity and motion of these particles, and their union in “corpuscles,” all bodies, and all their qualities and conditions, like color, magnetism, heat, and fire, arise by purely mechanical means and laws.

Fire was as fascinating to scientists as to dreamers at the hearth. What made a substance burn? How explain those ever-changing tongues of flame, beautiful, imperious, and terrible? In 1669 a German chemist, Johann Joachim Becher, reduced all “elements” to two—water and earth; one form of the latter he called “oily earth,” which he believed present in all combustible bodies; this it was that burned. In the eighteenth century Georg Stahl, following this false lead, was to set chemistry askew for decades with his similar theory of “phlogiston.” Boyle took another cue. Noting that various burning substances ceased to burn in a vacuum, he concluded that “there is in the air a little vital quintessence . . . which serves to the refreshment and restoration of our vital spirits.” 48His younger contemporary John Mayow, also of the Royal Society, advanced (1647) toward our current theory of fire by positing among the constituents of air a substance that unites with metals when they are calcined (oxidized); and he believed that a similar substance, entering our bodies, changes venous into arterial blood. A hundred years had to pass before Scheele and Priestley would definitely discover oxygen.

About 1670 a German alchemist, Hennig Brand, discovered that he could obtain from human urine a chemical that glowed in the dark without preliminary exposure to light. A Dresden chemist, Kraft, exhibited the new product before Charles II at London in 1677. Boyle drew from the secretive Kraft only the admission that the luminous substance “was somewhat that belonged to the body of man.” 49 The hint proved enough: Boyle soon obtained his own supply of phosphorus, and by a series of experiments he established all that is yet known about the glowing of that element. The new product cost its purchasers six guineas ($315?) per ounce, despite the abundance of the source.

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