400 



NATURE 



[August 27, 189] 



recall the services of Boyle, not, however, on account of the 

 coincidence of date, but because with him a new era in chemistry 

 began. He knew too much about the marvellous action of 

 "traces" of elements on masses of metal to feel justified in 

 pronouncing absolutely against the possibilities of transmutation, 

 but he did splendid service by sweeping away the firm belief 

 that metals consist of sulphur, salt, and mercury, and by giving 

 us the definition of an element. He recognized the prepon- 

 derating influence of metallurgy in the early history of science, 

 and quaintly tells us that "those addicted to chemistry have 

 scarce any views but to the preparation of medicines or to the 

 improvement of metals," a statement which was perfectly cor- 

 rect, for chemistry was built up on a therapeutic as well as a 

 metallurgic basis. The fact is, however, that neither the prepa- 

 ration of materials to be employed in healing, nor the study of 

 their action, had anything like the influence on the growth of 

 theoretical chemistry which was exerted by a few simple metal- 

 lurgical processes. Again, strange as it may seem, theoretical 

 chemistry was more directly advanced by observations made in 

 connection with methods of purifying the precious metals, and 

 by the recognition of the quantitative significance of the results, 

 than by the acquisition of facts incidentally gathered in the 

 search for a transmuting agent. The belief that chemistry 

 "grew out of alchemy" nevertheless prevails, and has found 

 expression in this Section of the British Association. As a fact, 

 however, the great metallurgists treated the search for a trans- 

 muting agent with contempt, and taught the necessity of investi- 

 gation for its own sake. George Agricoia, the most distinguished 

 of the sixteenth century metallurgists, in his work " De Ortu et 

 Causis Subterraneorum " (lib. v.), written about the year 1539, 

 disdainfully rejects both the view of the alchemists that metals 

 consist of sulphur and mercury, and their pretended ability to 

 chaiige silver irito gold by the addition of foreign matter. 



Biringuccio (1540) says, " I am one of those who ignore the 

 art of the alchemists entirely. They mock nature when they 

 say that with their medicines they correct its defects, and 

 render imperfect metals perfect." "The art," he adds, "was 

 not worthy of the consideration of the wise ancients who strove 

 to obtain possible things." In his time, reaction between 

 elements meant their destruction and reconstitution ; neverthe- 

 less, his sentence "transmutation is impossible, because in 

 order to transmute a body you must begin by destroying it 

 altogether," suggests that he realized the great principle of the 

 conservation of mass upon which the science of chemistry is 

 based. We have also the testimony of the German metallurgist, 

 Becher, who improved our tin-smelting in Cornwall. He is 

 said to have caused a medal to be struck in 1675, which bore 

 the legend, " Hanc unciam argenti finissimi ex plumbo arte 

 alchymica transmutavi," though he should have been aware that 

 he had only extracted the precious metal from the lead, and had 

 not transrnuted the base one. This is a lapse which must be 

 forgiven him, for his terra piiigtiis was the basis of the theory of 

 phlogiston, which exerted so profound an influence for a century 

 after his death, and he wrote, " I wist that I have got hold of 

 my pitcher by the right handle, for the pseudo- chemists seek 

 gold, but I have the true philosophy, science, which is more 

 precious." 



At this critical period what was Boyle doing when the theory 

 of phlogiston dawned in the mind of the metallurgist Becher ? 

 In 1672. Boyle wrote his paper on " Fire and Flame weighed in 

 the Balance," and came to the conclusion that the "ponderous 

 parts of flame " could pass through glass to get at melted lead 

 contained in a closed vessel. It has been considered strange 

 that he did not interpret the experiment correctly, but he, like 

 the phlogistic chemists, tried to show that the subtilis ignis, the 

 material of fire or phlogiston, would penetrate all things, and 

 could be gained or lost by them. Moreover, his later experi- 

 ments showed him that glass was powerles'; to screen iron from 

 the " effluvium of a loadstone." His experiment with lead heated 

 in a closed glass vessel was a fundamental one, to which his 

 mind would naturally revert if he could come back now and 

 review the present state of our knowledge in the light of the in- 

 vestigations which have been made in the two centuries that have 

 passed since his own work ceased. If he turned to the end of 

 the first century after his death he would see that the failure 

 to appreciate the work of predecessors was as prevalent in the 

 eighteenth century as in the sixteenth. The spirit of intolerance 

 which lead Paracelsus to publicly burn, in his inaugural lecture 

 at Basle, the works of Galen, Hippocrates, and Avicenna, 

 urvived in the eighteenth century, when Madame Lavoisier 



NO. I 139, VOL. 44] 



burnt the works of Stahl, but it was reserved for the nineteenth 

 century to reverently gather the ashes, recognizing that when the 

 writers of the school of Becher spoke of phlogiston they meant 

 what we understand by potential energy. 



If Boyle, finding that the Fellows of the Royal Society had 

 not carried out their intention to build a " Repository and 

 Laboratory," sought the School of Mines and came to the Royal 

 College of Science, he would surely thank my colleague. Prof. 

 Thorpe, for his vigorous defence last year, as President of this 

 Section, of the originality of the work of Priestley and Caven- 

 dish, to which Boyle's own researches had directly led. We on 

 our part, remembering Berzelius's view that "oxygen is the 

 centre point round which chemistry revolves," would hope to 

 interest him most by selecting the experiments which arose out 

 of the old metallurgical operation of separating the precious 

 metals from lead by " cupellation." When, in conducting this 

 operation, lead is heated in the presence of air, it becomes con- 

 verted into a very fluid dross. Boyle had, in 1661, taken this 

 operation as the very first illustration in his " Sceptical Chemist" 

 in proof of his argument as to the elemental nature of metals. 

 He would remember the quantitative work of Geber in the 

 eighth century, who stated that the lead so heated in air ac- 

 quired a "new weight," and he would appreciate the constant 

 reference to the operation of cupellation from the close of the 

 sixth century B.C., when the prophet Jeremiah wrote, to the 

 work of Jean Rey in 1629, whose conclusions he would wish he 

 had examined more closely. Lord Brouncker, as first President 

 of the Royal Society, had called attention to the increase in 

 weight of the lead in the " coppels" in the Assay Office in the 

 Mint in the Tower, and Majo had shown that the increase in 

 weight comes from a distinct " spiritus " in the air. Boyle would 

 incidentally see that Newton had accepted office in the Mint, 

 where he doubtless continued his experiments on calcination, 

 begun some time before, and, as if to mark his interest in the 

 operation of assaying, figures are represented on a bas-relief on 

 his tomb in Westminster Abbey as conducting cupellation in a 

 muffle. Iheoldworkmerges wonderfully into the new. Chevreul, 

 in the nineteenth century, confirms Otto Tachens's view in the 

 seventeenth, as to the saponifying action of litharge. Deville 

 employs molten litharge to absorb oxygen dissociated from its 

 compounds, and Graham, by extracting occluded gases from iron 

 and other metals, proves the accuracy of the old belief that elastic 

 fluids can freely permeate even solid metals. 



We may imagine with what vivid interest Boyle would 

 turn, not merely to the results of Priestley's work, but to his 

 methods. Priestley had decomposed litharge with the electric 

 spark, and had satisfied himself in 1774 by heating red lead 

 that the gas he obtained in his earlier experiments was really the 

 one now called oxygen. 



Boyle would see, that in the period 1774-77 Lavoisier, being at- 

 tracted by the "sceptical chemist's" own experiment on the heat- 

 ing of lead in closed vessels, overthrew the phlogistic theory, and 

 placed chemistry on a firm basis by showing that the increase in 

 weight of lead and tin, when heated in air, represents exactly 

 the weight of the gaseous body added ; and, finally, Dalton 

 having developed the atomic theory and applied it to chemistry, 

 Berzelius made lead memorable by selecting it for the first deter- 

 mination of an atomic weight. 



Without diverting his attention from the phenomena of oxida- 

 tion, Boyle would find questions the interest of which is only 

 equalled by their present obscurity. He would contemplate the 

 most interesting phase of the history of chemical science, de- 

 scribed by Van 't Hoff" as that of its evolution from the descriptive 

 to the rational period, in the early days of which the impossi- 

 bility of separating physics and chemistry became evident, and 

 Boyle would find that chemistry is now regarded from the point 

 of view of the mechanics of the atoms. 



Deville's experiments on dissociation have rendered it possible 

 to extend to the groups of atoms in chemical systems the laws 

 which govern the fusion and vaporization of masses of matter, 

 and this has produced a revolution comparable in its importance 

 to that which followed the discovery of the law of definite pro- 

 portions, for dissociation has shown us that true cau.-es of chemi- 

 cal change are variations of pressure and of temperature. For 

 instance, oxygen may be prepared on an industrial scale from 

 air by the intervention of oxide of barium heated to a constant 

 temperature of 700°, provided air be admitted to the heated 

 oxide of barium, under a pressure of ij atmospheres, while the 

 oxygen, thus absorbed, is evolved if the containing vessel be 

 rendered partially vacuous. It will be evident, therefore, that 



