History of Chemistry (Thorpe)

History of Chemistry by Sir Thomas Edward Thorpe was written in 2 volumes: Vol. I. From the Earliest Times to the Middle of the Nineteenth Century (1909); and Vol. II. From 1850 to 1910 (1910).

• Chemistry, as an art, was practised thousands of years before the Christian era; as a science, it dates no further back than the middle of the seventeenth century.

• The monumental records of Egypt and the accounts left us by Herodotus and other writers show that the ancient Egyptians... had a considerable knowledge of processes essentially chemical in their nature. ...The operations of chemistry as performed by them were of the nature of manufacturing processes, empirical in character and utilitarian in result.

• China, India, Chaldæa have each in turn been regarded as the birthplace of the various technical processes from which chemistry may be said to have taken its rise. Nevertheless, it is mainly from Egyptian records, or from writings avowedly based on... Egyptian sources, that such knowledge... is derived.

• [T]he word "chemistry" has its origin in chêmi, "the black land," the ancient name for Egypt. The art... was constantly spoken of as the "Egyptian art."

• Boerhaave gathers that chemistry was... originally denominated because it was considered of old as "not fit to be divulged to the populace, but treasured up as a religious secret"

• [The] legend of the " feministic" origin of chemistry is... much older than the fifth century of our era, and is but a variant of that which, according to Jewish writers, led to the expulsion of man from Paradise. A similar myth was current among the Phoenicians, Persians, Greeks, and Magi. ...Some of the ecclesiastics who elaborated these myths included the use of charms, a knowledge of gold and silver and precious stones, the art of dyeing, of painting the eyebrows, etc. the kind of arcana, in fact, which women in all ages were presumably most keen to know.

• [H]owever, in all allusions to chemia, even after the translation of the seat of the Roman Empire to Constantinople, it is implied that a knowledge of it was a sacred mystery, to be known only to the priesthood, and jealously guarded by them. It was characteristic of writers who had affixed an eternal stigma on Eve to make the sex in general answerable for an illicit knowledge of "things unfit for men to know."

• [C]hemistry originated with men, and it was not so much in the love of women as of wine that it took its rise.

• The manufacture of alcohol by processes of fermentation is probably the oldest of the chemical arts. The word vine means, in fact, a product of fermentation. ...[T]he ancient Egyptians ascribed the origin of wine to Osiris. It was a sacrificial offering even in the earliest times, as was bread. Wine seems to have been prepared by the Chinese as far back as the time of the Emperor Yü, circa 2220 B.C. Beer was manufactured in Egypt in the time of Senwosret III... B.C. 1880.

• The Egyptians were skilled in dyeing and in the manufacture of leather, and in the production and working of metals and alloys. They were familiar with the methods of tempering iron. They made glass, artificial gems, and enamels.

• [I]t is through [the Jews] and the Phoenicians, who were among the earliest of traders, that Europe was gradually made acquainted with many technical products of Eastern origin.

• Gold was undoubtedly one of the earliest metals to be made use of by men, as it probably was one of the first to be discovered. It occurs free in nature, and is met with in many rocks and in the sands of rivers. Its colour, lustre, and density would early attract attention... its malleability and ductility and the ease with which it could be fashioned, together with its unalterability, would render it valuable.

• Ethiopian and Nubian gold were known from the earliest times, and quartz crushing and gold washing were practised by the Egyptians. Representations of these processes have been found on Egyptian tombs dating from 2500 B.C. Gold-wire was used by the Egyptians for embroidery, and they practised plating, gilding, and inlaying as far back as 2000 B.C.

• Silver... like gold, to have been coined into money. It was originally known as "white gold." Some of the oldest coins in existence are alloys of silver and gold, obtained probably by the fusion of naturally occurring argentiferous gold, such as the pale gold of the Pactolus. Such an alloy was termed electrum, from its resemblance in colour to amber.

• Copper is also found to a limited extent in the metallic state, but probably the greater part of that used by the ancients was obtained from its ores, which are comparatively abundant and readily smelted. It was also used for coinage by the Egyptians, and was fashioned by them into a variety of utensils and implements. The older writers drew no clear distinction between copper, bronze, and brass...

• Pure copper is too soft a metal to be used for swords and cutting instruments, but copper ores frequently contain associated metals, as, for example, tin, which would confer upon the copper the necessary hardness to enable it to be fashioned into weapons. Such copper would be of the character of bronze, and it was known to the early workers that the nature of the metal was greatly modified by the selection of ores from particular localities.

• It was comparatively late in the metallurgical history of copper that bronze was produced by knowingly adding tin to the metal.

• Aurichalcum, or golden copper that is, brass was well known to the early workers in copper, and was made in Pliny's time by heating together copper, cadmia (calamine), and charcoal.

• Bell metal was employed by the Assyrians, and bronze was cast by the Egyptians for the manufacture of mirrors, vases, shields, etc., as far back as 2000 B.C.

• Tin... known to the early Egyptians, would appear to have been first obtained from the East Indies, and to have been known under the Sanskrit name of Kastîra (Kâs, to shine), whence... the Arabic word for tin, Kàsdir, and the Greek κασσιτερος, used by Homer and Hesiod.

• Tin ores are found in Britain (Cornwall), and were brought thence by the Phoenicians.

• The Latin word for tin was stannum; it was also known as plumbum album, in contradistinction to lead, which was called plumbum nigrum. Tin was used by the Romans for covering the inside of copper vessels, and was also occasionally employed in the construction of mirrors.

• Lead was well known to the Egyptians. In Pliny's time it was mainly procured from Spain and from Britain (Derbyshire).

• Leaden pipes were used by the Romans for the conveyance of water, and sheet lead was employed by them for roofing purposes. Argentarium was composed of equal parts of lead and tin; tertiarium, used as a solder, consisted of two parts of lead and one part of tin.

• Iron, although now the most important of the common metals, was not in general use until long after the discovery of gold, silver, and copper. ...[A]lthough its ores are relatively abundant and widely distributed, its extraction as a metal demanded greater skill and more appliances... Metallic iron was, however, well known to the Egyptians, who employed it in the manufacture of swords, knives, axes, and stone-chisels, both as malleable iron and as steel.

• Steel was... known to the Chinese as far back as 2220 B.C., and they were acquainted with the methods of tempering it. The good quality of Chinese steel caused it to be highly prized by Western nations.

• Mercury was familiar to Aristotle, and its mode of manufacture from cinnabar is described by Theophrastus (320 B.C.), who terms it "liquid silver." Processes of amalgamation were known to Pliny, who notes the readiness with which mercury dissolves gold. Pliny appears to distinguish the native metal found in Spain, which he terms argentum vivum (quicksilver), from that obtained by sublimation or distillation from cinnabar, which he calls hydrargyrum, from which we get the chemical symbol for mercury Hg.

• [M]etallic compounds were known to the ancients, and were employed by them as medicines and as pigments. The oxides of copper, known as flos œris, and scoria œris, obtained by heating copper bars to redness and exposing them to air, were used as escharotics. Verdigris, or œrugo, was made by the same methods as now. Blue vitriol, or chalcantum, is described by Pliny, who says that the blue transparent crystals are formed on strings suspended in its solution.
  • Note: escharotics are corrosive salves that can produce a thick dry scab, i.e., an eschar.

• Chrysocolla, malachite, or copper carbonate, was used as a green pigment. The blue κύανος of the Greeks, or cœruleum of the Romans, was obtained by fritting together alkali, sand, and oxide of copper. Botryitis, placitis, onychitis, ostracitis, were varieties of cadmia or oxide of zinc, obtained by calcining calamine, and were used in the treatment of ulcers, etc.

• Molybdena, which was the Latin name for litharge, was employed externally as an astringent and in the manufacture of plaster. The lead plaster employed by Roman surgeons was practically identical... with that in use to-day.

• Cerussa, or white lead, was made as now by exposing sheets of lead to the fumes of vinegar. It was used in medicine, as a pigment, and in the preparation of cosmetics.
  • Note: see also Cerussite.

• Cerussa usta was probably red lead. Its present name of minium was originally applied to cinnabar, the red sulphide of mercury, which was frequently adulterated with red lead.

• Cinnabar, formerly obtained from Africa, and, by the Romans, from Spain, was also used externally in medicine, and was a highly prized pigment, whose value was known to the Chinese from very early times.

• The black sulphide of antimony, the stimmi and stibium of Dioscorides and Pliny, was employed by women in Asia, Greece, and latterly in Western Europe, and is still so used in the East, for blackening their eyelashes. Preparations of antimony were used in medicine.

• Realgar, the scarlet sulphide of arsenic, the sandarach of Aristotle, and the arrenichon of Theophrastus, was employed as a pigment, and also in medicine, both internally and externally. The yellow sulphide of arsenic, or auri pigmentum (orpiment), was... used for the same purposes.

• A variety of yellow and red ochres, in addition to the pigments above... were used by painters, such as rubrica, an iron ochre of a dark red colour, and sinopis, or reddle, obtained from Egypt, Lemnos, and the Balearic Isles.

• Oxides of manganese were used as brown pigments.

• The white pigment, paratonium, was probably meerschaum. Melinum was a variety of chalk found in Samos.

• The ancients were well acquainted with indigo and madder, and with the mode of manufacturing lakes, which were employed by Grecian artists.

• The famous purpurissum was chalk or clay stained by immersion in a solution of Tyrian purple.

• Atramentum was lamp-black: ivory-black was used by Apelles, and was known as elephantinum. The ink of the ancients consisted of lamp-black suspended in a solution of gum or glue. The atramentum indicum, imported from the East, was identical with China ink.

• The ancients were well skilled in the art of dyeing, and even of calico printing. The Tyrians produced their famous purple dye as far back as 1500 B.C. It was obtained from shell-fish, mainly species of Murex, inhabiting the Mediterranean. Tyrian purple has been shown to be dibrom-indigo, and to have been produced by the action of air and light upon the juices exuded from the shell-fish.

• [T]he Egyptians were acquainted with the use of mordants ... [Pliny] accurately describes the process of madder dyeing on cotton, whereby a variety of fast colours—reds, browns, and purples—can be obtained from the same vat by the employment of different mordants, such as alumina, oxide of iron, or oxide of tin, etc.
  • In addition, Thorpe also quoted Pliny the Elder here, as translated by Thomas Thomson, The History of Chemistry (1830) Vol. 1, and as on p. 93 of the (1835) two volume edition, where Thomson adds, "It is evident that these substances applied were different mordants which served to fix the dye upon the cloth..."

• [L]arge quantities of glass were exported to Greece and Rome from Egypt, mainly by Phoenicians. Aristophanes mentions it as hyalos, and speaks of it as the beautiful transparent stone used for kindling fire.

• The Egyptians made use of various metallic oxides in colouring glass. The hœmatinon of Pliny was a red glass coloured with cuprous oxide. Cupric oxide was used to colour glass green; and ancient blue glass has been found to contain cobalt. The costly vasa murrhina of the Romans, obtained from Egypt, probably consisted of fluorspar, identical with the Blue John of the Derbyshire mines.

• Soap (sapo) is mentioned by Pliny, but its detergent properties were apparently unknown to him. It appears to have been first made by the Gauls, who prepared it from the ashes of the beech and the fat of goats, and used it as a pomatum, as did the jeunesse d'oreé of Rome. Wood ashes, as well as natron, were, however, used by the ancients for their cleansing properties.

• Starch, acetic acid, sulphur, alumen or crude sulphate of alumina, beeswax, camphor, bitumen, naphtha, asphalt, nitrum (carbonate of soda), common salt, and lime, were all well known to the Egyptians, and were used by them for many of the purposes in which they are employed to-day.

• [T]he ancients possessed a considerable acquaintance with many operations of technical chemistry... Their methods were probably jealously guarded and handed down by successive members of the crafts as precious secrets. ...[T]he scientific spirit was not free to develop, for science depends essentially upon free inter-communication of facts ...Moreover, the great intellects of antiquity, for the most part, had little sympathy with the operations of artisans, who, at least among the Greeks and Romans, were, for the most part, slaves. Philosophers taught that industrial work tended to lower the standard of thought.

• The priests, in most ages, have looked more or less askance at attempts, on the part of the laity, to inquire too closely into the causes of natural phenomena. The investigation of nature in early times was impossible for religious reasons.

• The educated Greeks had no interest in observing or in explaining the phenomena of technical processes. However prone they might be to speculation, they had no inclination to experiment or to engage in the patient accumulation of the knowledge of physical facts. ...The influence of a spurious Aristotelianism, which lasted through many centuries and even beyond the time of Boyle, was wholly opposed to the true methods of science, and it was only when philosophy had shaken itself free from scholasticism that chemistry, as a science, was able to develop.

• Speculations as to the origin and nature of matter, and as to the conditions and forces which affect it, are to be found... in the oldest systems of philosophy... These speculations are not based... upon the systematic observation of natural phenomena. Still, as they appealed to human reason, they must be... founded upon experience, or at least not... consciously inconsistent with it.

• All the oldest cosmogonies regarded water as the fundamental principle of things: from Okeanos sprang the gods—themselves deified personifications of the "elements" or principles of which the world was made. ...[T]his doctrine of the origin and essential nature of matter came to be... associated with the name of Thales of Miletus... who, according to Tertullian, is to be regarded as the first of the race of the natural philosophers—that is, the first of those who made it their business to inquire after natural causes and phenomena. Thales... may have been influenced by the Egyptian teaching in the formulation of his cosmological theories.

• [T]he teaching of Thales... survived through the space of twenty-four centuries. It can be shown to have affected the course of chemical inquiry down to the close of the eighteenth century. It influenced the experimental labours of philosophers so diverse in character as Van Helmont, Boyle, Boerhaave, Priestley, and Lavoisier all of whom made attempts to prove or disprove its adequacy.

• Van Helmont... was one of the most strenuous supporters of the doctrine of Thales, and sought to establish it by observations which, in the absence of all knowledge of the true nature of air and water, seemed at the time irrefutable. ...[H]e planted a willow weighing 5 lbs. in 200 lbs. of earth previously dried in an oven. ...[A]t the end of five years it was found to weigh 169 lbs. 3oz., whereas the earth, after redrying, had lost only 2 oz... Hence, 164 lbs. ...had been produced seemingly from water alone. More than a century had to elapse before any clue to the true interpretation... was first furnished by the observations of Ingenhousz and Priestley.

• Although the idea of a primal "element" or common principle is to be found in every old-world philosophical system, the ancient philosophers were by no means in agreement as to its character. Anaximenes... taught that it was air, Herakleitos of Ephesus that it was fire, and Pherekides that it was earth.

• It was a comparatively simple evolutionary step to regard these principles or "elements" as mutually convertible. Anaximenes' theory of the formation of rain was an implicit admission of such convertibility. This philosopher taught that rain came by the condensation of clouds, which in their turn were formed by the condensation of air. Everything comes from air, and everything returns to air. That water might be converted by fire into air was surmised from the earliest times.

• [W]ater was everywhere recognised to disappear or to pass into the air under the influence of fire or solar heat. The supposition had grown into a fixed belief in the Middle Ages. Even Priestley, as late as the end of the eighteenth century, imagined for a time that he had obtained proof of such a mutual conversion.

• The possibility of the transmutation of water into earth was a belief current through twenty centuries, and was only definitely and finally disproved by Lavoisier in 1770.

• The conception of fire as the primal principle has its germ in the fire- or sun-worship of the Chaldeans, Scythians, Persians, Parsees, and Hindus; and it is not difficult to trace, therefore, how heat came to be regarded either as antecedent to, or as associated with, the other primal principles.

• Empedokles... was the first whose name has come down to us to reintroduce the definite conception of four primal elements—fire, air, water, and earth. These he regarded as distinct, and incapable of being transmuted, but as forming all varieties of matter by intermixture in various proportions. These principles he deified, Zeus being the personification of the element of fire, Here of air, Nestis of water, and Aidoneous of earth.

• The doctrine of the four elements was also adopted by Plato and amplified by Aristotle... [who] exercised an authority almost supreme in Europe during nearly twenty centuries. His influence is to be traced throughout the literature of chemistry long after the time of Boyle. It may be detected even now. ...His theory of the nature of matter is contained in his treatise on Generation and Destruction. It mainly differed from that of Empedokles in regarding the four "elements" as mutually convertible. Each "element" or principle was regarded as being possessed of two qualities, one of which was shared by another element or principle.
  Thus: Fire is hot and dry; air is hot and wet; water is cold and wet; earth is cold and dry.
  In each primal "element" one quality prevails. Fire is more hot than dry; air is more wet than hot; water is more cold than wet; earth is more dry than cold. ...[I]f the dryness of fire is overcome by the moisture of water, air is produced; if the heat of air is overcome by the coldness of earth, water is formed; if the moisture of water is overcome by the dryness of fire, earth results. Ancient chemical literature contains many illustrations or diagrams symbolising the convertibility or mutual relations....

• [T]he founder of [the Peripatetic school], a descendant of Esculapius, and undoubtedly one of the greatest and most enlightened thinkers of antiquity, was an ideal man of science. ...Much of what is called Aristotelianism is entirely foreign to the spirit of the teaching of Aristotle. The Aristotelians of the Middle Ages were mainly dialecticians, and almost wholly concerned with the formulae of syllogistic inference, and without real sympathy with, or knowledge of, his system. Much... that was attributed to him, and which was venerated accordingly, is undoubtedly spurious. The fame of the Master has consequently suffered at the hands of those who, calling themselves Peripatetics, were in no proper sense followers of his method or interpreters of his dogma.

• Aristotle affirmed that natural science can only be founded upon a knowledge of facts, and facts can only be ascertained through observation and experiment.

• It is erroneous and unjust... to suppose that Aristotle's philosophy, as he taught it, is opposed to the true methods of science.

• A knowledge of Aristotle's works was transferred by Byzantine writers to Egypt; and, when that land was overrun by the Arabs in the seventh century, they adopted his system, spreading it abroad wherever their conquests extended. In the eighth century they carried it into Spain, where it flourished throughout their occupation of that country.

• From the ninth to the eleventh century the greater part of Europe was in a state of barbarism. The Moslem caliphate in Spain, under the beneficent rule of [emirs] Jusuf and Jaküb, alone preserved science from extinction. Cordova, Seville, Grenada, and Toledo were the chief seats of learning in Western Europe; and it was mainly through "the perfect and most glorious physicist," the Moslem Ibn-Roshd—better known as Averroes... that Christian scholiasts like Roger Bacon acquired their knowledge of the philosophical system of Aristotle, and mainly through the Moslems Geber and Avicenna that they gained acquaintance with the science of the East.

• The conception that matter is made up of particles or atoms, and that these particles are in a state of ceaseless motion, is to be met with in Hindu and Phoenician philosophy. It was taught by Anaxagoras, Leukippos, and Demokritos to the Greeks, and by Lucretius to the Romans.

• Leukippos and Demokritos explained the creation of the world as due solely to physical agencies without the intervention of a creative intelligence. According to their theories, the atoms are variable not only in size, but in weight. The smallest atoms are also the lightest. Atoms are impenetrable; no two atoms can simultaneously occupy the same place. The collision of the atoms gives them an oscillatory movement, which is communicated to adjacent atoms, and these, in their turn, transmit it to the most distant ones.

• Anaxagoras taught that every atom is a world in miniature, and that the living body is a congeries of atoms derived from the aliments which sustain it. Plants are living things, endowed like animals with respiratory functions, and, like them, atomically constituted. This philosopher was so far in advance of his age that his countrymen accused him of sacrilege, and he only escaped death by flight.

• [T]he assumption that these atoms exert mutual attractions and repulsions is probably as old as the fundamental conception itself. ...[S]o far as can be traced, the conceptions of atoms and atomic motion are indissolubly connected.

• [We cannot] now concern ourselves with the old metaphysical quibble of its divisibility or indivisibility. It may be, as Lucretius said, that the original atom is very far down.

• It may be that the physical atom is something which is not divided, not something that cannot be divided. This theory, dimly perceived in the mists of antiquity, has grown and strengthened with the ages, and in its modern application to the facts of chemistry has acquired a precision and harmony unimagined even by the poets and thinkers of old. ...[T]he whole course of the science has been controlled, illumined, and vivified by it. [T]he chemistry of to-day is one vast elaboration of this primeval doctrine.

• The latter half of the seventeenth century was a remarkable period... [N]early every department of human knowledge seemed to have become permeated by an eager spirit of scepticism, inquiry, and reform. The foundation of the Royal Society of London for Improving Natural Knowledge, the Accademia del Cimento of Florence, the Academie Royale at Paris, the Berlin Academy, all within a few years of each other, was significant of the times. Chemistry was no longer to be a sacred mystery, to be known only to priests, and its secrets jealously guarded by them.

• [P]urely deductive methods of the Peripatetics gradually gave place to the only sound method of advancing natural knowledge.

• The supremacy of the old philosophy may be said to have been first distinctly challenged by Robert Boyle. The appearance in 1661 of his book, The Sceptical Chemist, marks a turning-point in the history of chemistry.

• The "Chemico-physical Doubts and Paradoxes" raised by Boyle "touching the experiments whereby vulgar Spagyrists are wont to endeavour to evince their Salt, Sulphur, and Mercury to be the true Principles of Things," eventually sealed the fate of the doctrine of the tria prima, and of the tenets of the school of Paracelsus.

• In this treatise Boyle sets out to prove that the number of the peripatetic elements or principles hitherto assumed by chemists is, to say the least, doubtful.

• The words "element" and "principle" are used by him as equivalent terms, and signify those primitive and simple bodies of which compounds may be said to be composed, and into which these compounds are ultimately resolvable.

• He concludes... that the Paracelsian elements—their "salt," "sulphur," and "mercury"—are not the first and most simple principles of bodies; but that these consist, at most, of concretions of corpuscles or particles more simple than they, and possessing the radical and universal properties of volume, shape, and motion.

• He became a member of what was known as the Invisible College, a small association of men interested in the new philosophy, who met at each other's houses in London, and occasionally at Gresham College, "to discourse and consider of philosophical inquiries and such as related thereunto." The meetings were subsequently held in Oxford, and Boyle took up his residence there in 1654. Here—in association with Wilkins; John Wallis and Seth Ward, the two Savilian Professors of Geometry and Astronomy; Thomas Willis, the physician, then student of Christ Church; Christopher Wren, then Fellow of All Souls' College; Goddard, Warden of Merton; and Ralph Bathurst, Fellow of Trinity, and afterwards its President—they sought to cultivate the new philosophy, "being satisfied that there was no certain way of arriving at any competent knowledge unless they made a variety of experiments upon natural bodies. In order to discover what phenomena they would produce, they pursued that method by themselves with great industry, and then communicated their discoveries to each other." The Invisible College eventually grew into the Royal Society...

• He introduced the air-pump into England, and his "pneumatical engine" enabled him to discover many of the fundamental properties of a gas, notably the relation of its volume to pressure.

• He... discovered the dependence of the boiling point of a liquid upon atmospheric pressure, explained the action of the syphon, the effect of the air on the vibration of a pendulum and on the propagation of sound, and made experiments on the nature of flame, and on the relation of air to combustion and respiration.

• In his History of Fluidity he seeks to show that a body seems to be fluid by consisting of corpuscles touching one another only in some parts of their surfaces; whence, by reason of the numerous spaces between them, they easily glide along each other till they meet with some resisting body to whose internal surface they exquisitely accommodate themselves. He considers the requisites of fluidity to be chiefly these: The smallness of the component particles, their determinate figure, the vacant spaces between them, and the fact of their being agitated variously and apart by their own innate motion or by some thinner substance which tosses them about in its passage through them.

• His published works contain many well-authenticated chemical facts, which are commonly held to be the discovery of a later time.

• He prepared acetone by the distillation of the acetates of lead and lime; and he isolated methyl alcohol from the products of the destructive distillation of wood.

• He was one of the earliest to insist on the necessity of studying the forms of crystals. He saw in their formation proof that the internal motions, configuration, and position of the integral parts are all that is necessary to account for alterations and diversities in outward character.

• Some of the stock illustrations of our lecture-rooms were of his contrivance. Thus he illustrated the expansive power of freezing water by bursting a plugged gun-barrel filled with water by solidifying the water by means of a mixture of snow and salt a freezing mixture which he first introduced.

• Boyle was the first to formulate our present conception of an element in contradistinction to that of the Greeks and the schoolmen who influenced the theories of the iatro-chemists. In the sense understood by him, the Aristotelian elements were not true elements, nor were the salt, sulphur, and mercury of the school of Paracelsus.

• He was... the first to define the relation of an element to a compound, and to draw the distinction we still make between compounds and mixtures.

• He revived the atomic hypothesis, and explained chemical combination on the basis of affinity.

• He contended that one of the main objects of the chemist was to ascertain the nature of compounds; and thereby he stimulated the application of analysis to chemistry. Boyle discovered a number of qualitative reactions, and applied them to the detection of substances, either free or in combination.

• Boyle's greatest service to learning consisted in the new spirit he introduced into chemistry. Henceforward chemistry was no longer the mere helpmeet of medicine. She became an independent science, the principles of which were to be ascertained by experiment; a science to be studied with the object of discovering the laws regulating the phenomena with which it is concerned and hence elucidating truth for truth's sake.

• The old philosophy of the Greeks had, as we have seen, become merged into the doctrine of the iatro-chemists; and this was now to be purified from the theosophical mysticism with which Paracelsus and his followers had enshrouded it. "The dialectical subtleties of the schoolmen much more," says Boyle, "declare the wit of him that uses them than increase the knowledge or remove the doubts of sober lovers of truth... For in such speculative inquiries where the naked knowledge of the truth is the thing principally aimed at, what does he teach me worth thanks, that does not, if he can, make his notion intelligible to me, but by mystical terms and ambiguous phrases darkens what he should clear up, and makes me add the trouble of guessing at the sense of what he equivocally expresses, to that of learning the truth of what he seems to deliver."

• The influence of the new spirit... infused into the science by Boyle is seen in the general style of chemical literature at the end of the seventeenth century, when compared with that of the close of the sixteenth. The mysticism and obscurity of the alchemists were no longer tolerated.

• Kunkel did much to liberate chemical literature from the mysticism and obscurity of alchemy. He was scornful of the theories of the adepts, and contemptuous of their tria prima.

• Kunkel discovered the secret of the manufacture of aventurine glass and of ruby glass by means of the purple of Cassius a product from gold first obtained by a doctor of medicine of that name in Hamburg.

• He made observations on fermentation and putrefaction recognised that alum was a double salt (sal duplicatum); described the present method of preparing pure silver, and of parting gold and silver by means of sulphuric acid. He also described the mode of preparing a number of essential oils, detected the presence of stearopten in oils, and discovered nitrous ether.

• Becher's name is remembered mainly in connection with his theory of combustion, which... was subsequently developed by Stahl into the theory of Phlogiston—a generalisation which dominated chemistry until near the close of the eighteenth century.

• John Mayow... was a practising physician, whose name chiefly lives by virtue of his clear recognition of the substance or principle in the air which is concerned in combustion, the calcination of metals, respiration, and the conversion of venous into arterial blood. This substance, which he found to be contained in saltpetre, he called spiritus igno-aëreus or nitro aëreus.

• Had he been able to follow up his observations, he might have influenced very materially the development of theoretical chemistry. As it was, he was practically overlooked by his contemporaries, and the real significance of his work was not appreciated until long afterwards.

• Nicolas Lemery... wrote a Cours de Chimie, one of the best text-books of the time... and was translated into English, German, Latin, Italian, and Spanish. In this book he strove... to express himself clearly, and to avoid the obscurities which were to be found in the authors who had preceded him.

• Nicolas Lemery... made a considerable number of contributions to pharmaceutical chemistry; and his Pharmacopée Universelle, Dictionnaire Universel des Drogues Simples, and Traité de l'Antimoine were standard works in their day.

• In 1682 he was invited to Paris by Colbert, and in 1691 was made a member of the Academy and was placed by the Duke of Orleans in charge of his laboratory—then one of the finest in Europe.

• Homberg married the daughter of Dodart, the physician. She became an expert preparateur, and was of great assistance to him in his experimental inquiries.

• He first made known the existence of phosphorus in France, discovered by Brand, of Hamburg, and he described the phosphorescent salt [Homberg's phosphorus] associated with his name.

• He made important observations on the saturation of alkalis by acids, and was aware that they combined in different proportions.

• Next to Boyle, perhaps the most active agent in emancipating chemistry from the yoke of alchemy was Boerhaave...

• As a chemist Boerhaave is chiefly known by his Elementa Chemia,... the most complete and most luminous chemical treatise of its time, translations of which appeared in the chief European languages.
  ...The first [part] is concerned with the origin and progress of the art, and with the personal history of its most distinguished cultivators. The second... part deals with the attempt to form a system of chemistry based on such observational matter as seemed well established. The third consists of a collection of chemical processes relating to the analysis or decomposition of bodies, grouped under the heads of "vegetables," "animals," and "fossils"—the beginnings... of a sub-division of the science into organic and inorganic chemistry.

• As regards his belief in alchemy, Boerhaave was an agnostic: he neither affirmed nor denied the possibility of transmutation. In this respect he resembled Newton and Boyle.

• Boyle, indeed, was singularly cautious and reticent in his references to alchemistic matters. As was said of him by Shaw, he was too wise to set any bounds to nature: he was not prone to say that every strange thing must needs be impossible, for he saw strange things every day, and was well aware that there are powerful forces in the world of whose laws and modes of action he knew nothing. With that wariness which was habitual to him, he was wont to say that "those who had seen them might better believe them than those who had not"; and he was modest enough to suppose that Paracelsus or Helmont might conceivably know of agents of which he was ignorant.

• Boerhaave unquestionably spent much time in the study of alchemical works, particularly those of Paracelsus and Helmont, which he repeatedly read.

• The Philosophical Transactions of the Royal Society contain the results of a laborious but fruitless investigation by him on quicksilver, which he undertook in the hope of discovering the seminal or engendering matter which, on the old theory of the generation of metals, was supposed to be contained in mercury. But although... he tortured it by "conquassation, trituration, digestion, and by distillation, either alone or amalgamated with lead, tin, or gold, repeating this operation to 511 or even to 877 distillations, "the mercury appeared only" rather more bright and liquid, without any other variation in its form or virtues, and acquired very little, if any, increase of its specific gravity."

• Stephen Hales... distinguished as a physiologist and inventor, occupied himself in chemical pursuits, and made a number of observations on the production of gaseous substances. His results were communicated to the Royal Society and subsequently republished, in a collected form, under the title of Statical Essays. In these experiments he used methods very similar in principle to those subsequently employed by Priestley.
  • Ref: Statical Essays, Vol. 1 & Vol. 2.

• [H]e must have prepared a considerable number of gaseous substances—hydrogen, carbonic acid, carbonic oxide, sulphur dioxide, marsh gas, etc.—but he seems to have made no systematic attempt to study their properties, as he considered that they were simply air, modified or "tinctured" by the presence of substances which he regarded as more or less fortuitous.

• Prior to the time of Black all forms of gaseous substance were regarded as substantially identical in fact, as being air, as understood by the Ancients a simple elementary substance. It was Black's study of carbonic acid which first clearly established that there were essentially distinct varieties of gaseous matter.

• The first year of the nineteenth century is further memorable on account of the invention of the voltaic pile, and by reason of its application by William Nicholson and Sir Anthony Carlisle to the electrolytic decomposition of water. This mode of resolving water into its constituents made a great sensation at the time, mainly because of the extraordinary method by which it was effected. It afforded an independent and unlooked-for proof of the compound nature of water by a method altogether differing in principle from that by which its composition had been previously ascertained.

• The formation of water by the combustion of hydrogen brought no conviction of its real nature to a confirmed phlogistian like Priestley; and it is even doubtful whether Cavendish ever fully realised the true significance of his great discovery. But the fact that the quantitative results of the analysis thus effected were identical with those of its synthesis, as made by Cavendish and Lavoisier, admitted of only one interpretation.

• This cardinal discovery may be said to have completed the downfall of phlogiston.

• The value of the voltaic pile as an analytical agent was... quickly appreciated... In the hands of Humphry Davy its application to the analysis of the alkalis and alkaline earths led to discoveries of the greatest magnitude.

• While in the capacity of assistant and operator in Beddoes's Pneumatical Institute, Davy discovered the intoxicating properties of nitrous oxide (so called laughing gas), which brought him into prominence and led to his engagement by the managers of the newly-created Royal Institution in London as lecturer in chemistry in succession to Garnett.

• He early began to experiment on galvanism, and soon succeeded in developing the fundamental laws of electro-chemistry; and in 1807 he effected the decomposition of [caustic] potash and [caustic] soda by the application of voltaic electricity thereby establishing... that the alkalis are compound substances. He subsequently proved that this was also the case with the alkaline earths. Davy thus added some five or six metallic elements to those already known.

• These discoveries, perhaps the most brilliant of their time, afforded additional evidence of the invalidity of Lavoisier's assumption that oxygen, as the name implies, was the "principle of acidity." The surmise, in fact, was already disproved by the case of water—a neutral substance [containing oxygen yet] devoid of all the recognised attributes of an acid. It was still further disproved by the cases of [caustic] potash and [caustic] soda—strongly alkaline compounds [yet both containing oxygen].

• Additional evidence was adduced by Davy in demonstrating, in 1810, that the so-called oxymuriatic acid, [i.e.,] the dephlogisticated marine acid discovered by Scheele, contained no oxygen, but was a simple, indivisible substance.

• For the old designation, which connoted a compound body, he substituted the name chlorine, in allusion to the characteristic colour of the element.

• In the course of his investigation on this substance he discovered the penta- and trichloride of phosphorus, chlorophosphamide, and chlorine peroxide. He was also the discoverer of telluretted hydrogen and an independent discoverer of nitrosulphonic acid.

• He worked on iodine and the iodates, on the diamond, on the so-called fuming liquor of Cadet, on nitrogen chloride, and on the pigments of the ancients. Lastly, he invented the miner's safety lamp...

• In the preceding volume an attempt was made to outline the significant features in the development of chemistry, as an art and as a science, from the earliest times down to about the middle of the last century. Since that time chemistry has progressed at a rate and to an extent unparalleled at any period of its history.

• Not only have the number and variety of chemical products inorganic and organic been enormously increased, but the study of their modes of origin, properties, and relations has greatly extended our means of gaining an insight into the internal structure and constitution of bodies.

• This extraordinary development has carried the science beyond the limits of its own special field of inquiry, and has influenced every department of natural knowledge. Concurrently there has been a no less striking extension of its applications to the prosperity and material welfare of mankind.

• With the death of Davy the era of brilliant discovery in chemistry, wrote Edward Turner, appeared for the moment to have terminated.

• Although the number of workers in the science steadily increased, the output of chemical literature in England actually diminished for some years; and, as regards inorganic chemistry, few first-rate discoveries were made during the two decades prior to 1850.

• Chemists seemed to be of Turner's opinion that the time had arrived for reviewing their stock of information, and for submitting the principal facts and fundamental doctrines to the severest scrutiny. Their activity was employed not so much in searching for new compounds or new elements as in examining those already discovered. The foundations of the atomic theory were being securely laid. The ratios in which the elements of known compounds are united were being more exactly ascertained. The efforts of workers, Graham excepted, seemed to be spent more on points of detail, on the filling-in of little gaps in the chemical structure, as it then existed, than in attempts at new developments.

• For a time—during the early 'thirties—chemists struggled with the claims of rival methods of notation, and it was only gradually that the system of Berzelius gained general acceptance. At none of the British universities was there anything in the nature of practical tuition in chemistry.

• Thomson, at Glasgow, occasionally permitted a student to work under him, but no systematic instruction was ever attempted. The first impulses came from Graham in 1837, when he took charge of the chemical teaching at the University of London, and when, in 1841, he assisted to create the Chemical Society of London.

• It was largely through the influence of [the following] master-minds that chemistry took a new departure. Prior to their time organic chemistry hardly existed as a branch of science: organic products, as a rule, were interesting only to the pharmacist mainly by reason of their technical or medicinal importance. But by the middle of the nineteenth century the richness of this hitherto untilled field became manifest, and scores of workers hastened to sow and to reap in it. The most striking feature, indeed, of the history of chemistry during the past sixty years has been the extraordinary expansion of the organic section of the science. The chemical literature relating to the compounds of carbon now exceeds in volume that devoted to all the rest of the elements.

• In the middle of the nineteenth century chemists began to concern themselves with the systematisation of the results of the study of organic compounds, and something like a theory of organic chemistry gradually took shape. From this period we may date the attempts at expressing the internal nature, constitution, and relations of substances which, step by step, have culminated in our present representations of the structure and spatial arrangement of molecules.

• In 1850 the dualistic conceptions of Berzelius ceased to influence the doctrines of organic chemistry. The enunciation by Dumas of the principle of substitution, and its logical outcome in the nucleus theory and in the theory of types, had not only effected the overthrow of dualism, but was undermining the position of the radical theory of Liebig and Wöhler.
  • Note: "dualism" asserted compounds were held together by the attraction of positive and negative electrical charges, making it inconceivable that a molecule composed of two electrically similar atoms—as in oxygen—could exist.

• The teaching of Gerhardt and Laurent had spread over Europe, and was influencing those younger chemists who, while renouncing dualism, were not wholly satisfied with a belief in compound radicals.

• Other representative men of the middle period of the nineteenth century, in addition to Williamson, were Graham and Bunsen. The three men were investigators of very different type, and their work had little in common. But each was indentified with discoveries of a fundamental character, constituting turning-points in the history of chemical progress, valuable either as regards their bearing on chemical doctrine or as regards their influence on operative chemistry.

• [In 1845 the] Royal College of Chemistry in London was founded and placed under the direction of August Wilhelm Hofmann—one of the most distinguished pupils of Liebig.

• Under his inspiration the study of practical chemistry made extraordinary progress, and discovery succeeded discovery in rapid succession. In bringing Hofmann to England we had, in fact, imported something of the spirit and power of his master, Liebig.

• Among the pupils and co-workers of Hofmann were Warren de la Rue, Abel, Nicholson, Mansfield, [Henry] Medlock, Crookes, [Arthur S.] Church, Griess, Martius, Sell, Divers, and Perkin.

• Whilst at Giessen he had begun the study of the organic bases in coal-tar with a view more especially of establishing the identity of Fritzsche's aniline with the benzidam of Zinin and the krystallin of Unverdorben.

• With Muspratt he discovered paratoluidine and nitraniline; with Cahours, allyl alcohol.

• His pupil Mansfield worked out, at the cost of his life, the methods for the technical extraction of benzene and toluene from coal-tar, and thereby made the coal-tar colour-industry possible.

• It was in attempting to synthesise quinine by the oxidation of aniline that Perkin, then an assistant at the college, obtained, in 1856, aniline purple or mauve, as it came to be called by the French, the first of the so-called coal-tar colouring matters.

• In 1859 this was followed by the discovery of magenta, or fuchsine, by [François-Emmanuel] Verquin. For its manufacture [Henry] Medlock, one of Hofmann's pupils, in 1860 devised a process by which for a time it was almost exclusively made. Hofmann studied the products thus obtained, and showed that they were derivatives of a base he called rosaniline; and he demonstrated that the colouring matters were only produced through the concurrent presence of aniline and toluidine. He also proved that the base of the dye, known as aniline blue, was triphenylrosaniline. As the result of these inquiries he obtained the violet or purple colouring matters known by his name [Hofmann's violets].

• [A]ll his classical work on the amines, ammonium compounds, and the analogous phosphorus derivatives was done at the Royal College of Chemistry.

• Prior to the establishment by Liebig, in 1826, of the Giessen laboratory, the state of chemistry in Germany was not much... better than [England's.] The creation of the Giessen school initiated a movement which has culminated in the pre-eminent position [of] Germany... in the chemical world. Students from every civilised country came to study and to work under its leader...

• Justus von Liebig... after graduating at Erlangen, where he worked on the fulminates, ...entered the [University of Paris] laboratory of Gay Lussac, with whom he continued his inquiries.

• Returning to Germany, he was appointed Professor of Chemistry at Giessen in 1826, and began those remarkable series of scientific contributions upon which the superstructure of organic chemistry largely rests.

• He investigated the cyanates, cyanides, ferrocyanides, thiocyanates, and their derivatives.

• In conjunction with Wöhler he discovered the group of the benzoic compounds and created the radical theory.

• With Wöhler... he investigated uric acid and its derivatives. He discovered hippuric acid, fulminuric acid, chloral, chloroform, aldehyde, thialdine, benzil, and elucidated the constitution of the organic acids and the amides.

• He greatly improved the methods of organic analysis, and was thereby enabled to determine the empirical formulae of a number of carbon compounds of which the composition was imperfectly known.

• He practically laid the foundations of modern agricultural chemistry, and to his teaching is due the establishment of an important branch of technology the manufacture of chemical fertilisers.

• He worked on physiological chemistry, especially on the elaboration of fat, on the nature of blood, bile, and on the juice of flesh.

• He studied the processes of fermentation, and of the decay of organised matter.

• He was a most prolific writer. The Royal Society's Catalogue of Scientific Papers enumerates... 317 contributions... He was the founder of the Annalen der Chemie... and of the Jahresbericht; he published an Encyclopedia of Pure and Applied Chemistry and a Handbook of Organic Chemistry. His Familiar Letters on Chemistry was translated into every modern language, and exercised a powerful influence in developing popular appreciation of the value and utility of science.

• With the name of Liebig that of Wöhler is indissolubly connected. Although the greater part of their work was not published in conjunction, what they did together exercised a profound influence on the development of chemical theory.

• After studying at Marburg, where he discovered, independently of Davy, cyanogen iodide, and worked on mercuric thiocyanate, he went to Heidelberg and investigated cyanic acid and its compounds, under the direction of Gmelin.

• In 1823 he worked with Berzelius at Stockholm, where he prepared some new tungsten compounds and practised mineral analysis.

• In 1825 he became a teacher of chemistry in the Berlin Trade School. Here he succeeded for the first time in preparing the metal aluminium and in effecting the synthesis of urea—one of the first organic compounds to be prepared from inorganic materials.

• Jointly with Liebig he worked upon mellitic and cyanic and cyanuric acids.

• In 1832 Wöhler, now appointed to the Polytechnic at Cassel, began with Liebig their memorable investigation on bitter almond oil.

• In 1836 he was called to the Chair of Chemistry in the University of Göttingen, and with Liebig attacked the constitution of uric acid and its derivatives the last great investigation the friends did in common.

• Wöhler subsequently devoted himself mainly to inorganic chemistry. He isolated crystalline boron, and prepared its nitrides, discovered the spontaneously inflammable silicon hydride, titanium nitride, and analysed great numbers of minerals and meteorites and compounds of the rarer metals.

• He made Gottingen famous as a school of chemistry. ...[U]pwards of 8000 students had listened to his lectures or worked in his laboratory.

• If Liebig could reckon among his pupils Redtenbacher, [Johann Conrad] Bromeis, [Franz] Varrentrapp, Gregory, Playfair, Williamson, Gilbert, Brodie, Anderson, Gladstone, Hofmann, [Heinrich] Will, and Fresenius; Dumas could point to [Félix-Polydore] Boullay, Piria, Stas, Melsens, Wurtz, and [Félix] Leblanc all of whom did yeoman service in developing the rapidly expanding branch of organic chemistry.

• Jean Baptiste André Dumas was born on July 14, 1800, at Alais, where he was apprenticed to an apothecary. In his sixteenth year he went to Geneva and entered the pharmaceutical laboratory of [Elie] Le Royer. Without, apparently, having received any systematic instruction in chemistry, he commenced the work of investigation.

• With Coindet he established the therapeutic value of iodine in the treatment of goître; with Prevost he attempted to isolate the active principle of digitalis [foxgloves], and studied the chemical changes in the development of the chick in the egg.

• In his twenty-fourth year Dumas went to Paris and became Répétiteur de Chimie at the École Polytechnique. He joined Audouin and Brongniart in founding the Annales des Sciences Naturelles, and began his great work on Chemistry Applied to the Arts... [published 1828]. At about this time he devised his method of determining vapour densities, and published the results of a number of estimations made by means of it.
  • Note: A Répétiteur de Chimie would be a teaching assistant position, and would repeat pivotal or historical experiments in chemistry lectures, and verify or demonstrate the validity of published experiments.

• With [Félix-Polydore] Boullay he began an inquiry on the compound ethers, out of which grew the etherin theory, which served as a stepping-stone to the theory of compound radicals subsequently elaborated by Liebig and Wöhler.

• Dumas discovered the nature of oxamide and of ethyl oxamate [${\displaystyle {\ce {C4H7NO3}}}$], isolated methyl alcohol, and established the generic connection of groups of similarly constituted organic substances, or, in a word, the doctrine of homology.

• His work on the metaleptic action of chlorine upon organic substances eventually effected the overthrow of the electro-chemical theory of Berzelius and led to the theory of types, which, in the hands of Williamson, Laurent, Gerhardt, and Odling, was of great service in explaining the analogies and relationships of whole groups of organic compounds.
  • Note: According to Dumas in Recherches de Chimie organique, p. 545-549, "[C]hlorine possesses the singular power of removing the hydrogen of certain bodies, replacing it atom for atom. This law of nature, this law or theory of substitutions... I propose to call... metalepsy, from μετάληψις, which expresses... that the body... has taken one element in place of another, chlorine in place of hydrogen, for example. Thus chloral is formed by substitution, or by metalepsy; it is one of the maleptic products of alcohol. ...acetic ether, acetic acid, formic acid are maleptic products of alcohol." Quoted by Henry Marshall Leicester, Herbert S. Klickstein, A Source Book in Chemistry, 1400-1900 (1952) "Researches in Organic Chemistry Relative to the Action of Chlorine in Alcohol." p. 322.

• He worked in every field of chemistry. He invented many analytical processes, established the gravimetric composition of water and of air, and revised the atomic weights of the greater number of the elements then known.

• Dumas exercised great influence in scientific and academic circles in France. He was an admirable speaker, and had rare literary gifts. On the creation of the Empire he was made a Senator, and was elected a member of the Municipal Council of Paris, of which he became president in 1859.

• Thomas Graham... after studying under Thomas Thomson at the University of [Glasgow], attended the lectures of Hope and Leslie in Edinburgh.

• In 1830 he succeeded Ure as teacher of chemistry at Anderson's College in Glasgow, and in 1837 was called to the Chair of Chemistry in the newly-founded University of London, in succession to Edward Turner. In 1854 he was made Master of the Mint.

• Graham's work was mainly devoted to... physical chemistry.

• His contributions to pure chemistry are few in number. By far the most important is his discovery of metaphosphoric acid and its relations to the other modifications of phosphoric acid. Ortho- or ordinary phosphoric acid was known to Boyle; pyrophosphoric acid was discovered by Clark.

• Graham's work is noteworthy as first definitely indicating the inherent property of the acids to combine with variable but definite amounts of basic substances by successive replacement of hydroxyl groups the property we now term basicity, and was of fundamental importance in regard to its bearing on the constitution of acids and salts.

• Graham's fame chiefly rests upon his discovery of the law of gaseous diffusion (1829-1831), upon his work on the diffusion of liquids, and upon his recognition of the condensed [metallic] form of hydrogen he termed hydrogenium. Questions involving the conception of molecular mobility... constituted the main feature of his inquiries.

• We owe to him, among others, the terms crystalloid, colloid, dialysis, atmolysis, occlusion—all of which have taken a permanent place in the terminology of science.

• Williamson's discovery, in 1850, of the true nature of ether and of its relation to alcohol, and his subsequent preparation of mixed ethers, served not only to reconcile conflicting interpretations of the process of etherification, but also to reconcile the theory of types with that of radicals.

• [H]is method of representing the constitution of the ethers and their mode of origin gave a powerful stimulus to the use of type-formulas in expressing the nature and relations of organic compounds.

• In 1840... Williamson entered the University of Heidelberg with the intention of studying medicine; but, under the influence of Leopold Gmelin, he turned to chemistry.

• In 1844 he went to Giessen, to work under Liebig, and there [he] made his first contributions to chemical science viz., on the decomposition of oxides and salts by chlorine; on ozone; and on the blue compounds of cyanogen and iron.

• After graduating at Giessen he went, in 1846, to Paris, where he came under the influence of Comte, with whom he studied mathematics.

• In 1850, at Graham's solicitation, he was appointed to the Chair of Practical Chemistry at University College, vacant by the death of Fownes. He at once embarked upon those researches which constitute his main contribution to science. In the attempt to build up the homologous series of the aliphatic alcohols from ordinary alcohol he succeeded in demonstrating the real nature of ether and its genetic relation to alcohol, and in explaining the process of etherification. The memoirs (1850-52) in which he embodied the facts had an immediate influence on the development of chemical theory. His explanation of the process of etherification familiarised chemists with the idea of the essentially dynamical nature of chemical change.

• He imported the conception of molecular mobility not only into the explanation of such metathetical reactions as the formation of the ethers, but into the interpretation of the phenomena of chemical change in general.

• In these papers, as also in one on the constitution of salts, published in 1851, he attempted to systematise the representation of the constitution and relations of oxidised substances—organic and inorganic—by showing how they may be regarded as built up upon the type of water considered as ${\displaystyle {\ce {^{H}_{H}O}}}$, in which the hydrogen atoms are replaced, wholly or in part, by other chemically equivalent atoms. This idea was immediately adopted by Gerhardt, was further elaborated by Odling and Kekulé, and was eventually developed into a theory of chemistry.

• [A]fter studying chemistry under Stromeyer, the discoverer of cadmium, [he] went to Paris and worked with Gay Lussac.

• In In 1836 he succeeded Wöhler as teacher of chemistry in the Polytechnic School of Cassel, and in 1842 became Professor of Chemistry in the University of Marburg. In 1852 he was called to Heidelberg, and occupied the Chair of Chemistry there until his retirement in 1889.

• Bunsen first distinguished himself by his classical work on the cacodyl compounds, obtained as the result of an inquiry into the nature of the so-called "fuming liquor of Cadet," an evil-smelling, highly poisonous, inflammable liquid formed by heating arsenious oxide with an alkaline acetate. The investigation (1837-1845) is noteworthy, not only for the skill it exhibits in dealing with a difficult and highly dangerous manipulative problem, but also for the remarkable nature of its results and on account of their influence on contemporary chemical theory. The research, in the words of Berzelius, was the foundation-stone of the theory of compound radicals. The name cacodyl or kakodyl was suggested by Berzelius in allusion to the nauseous smell of the compounds of the new radical arsinedimethyl, ${\displaystyle {\ce {As(CH3)2}}}$, as it was subsequently termed by Kolbe.

• Bunsen greatly improved the methods of gasometric analysis; these he applied, in conjunction with Playfair, to an examination of the gaseous products of the blast furnace in the manufacture of iron, and thereby demonstrated the enormous waste of energy occasioned by allowing the gases to escape unused into the air, as was then the universal practice. This inquiry effected a revolution in the manufacture of iron as important, indeed, as that due to the introduction of the hot blast.

• Bunsen devised methods for determining the solubility of gases in liquids, for ascertaining the specific gravity of gases, their rates of diffusion, and of combination or inflammation.

• In 1841 he invented the carbon-zinc battery, and applied it to the electrolytic production of metals, notably of magnesium, the properties of which he first accurately described.

• In 1844 he contrived the grease-spot photo-meter, which was long in general use for ascertaining the photometric value of illuminating gas.

• His methods of ascertaining the specific heats of solids and liquids were simple, ingenious, and accurate.

• In 1855-1863 he carried out, in conjunction with Roscoe, a long series of investigations on the chemical action of light.

• In 1859, in association with Kirchhoff, he devised the first methods of spectrum analysis, and explained this origin and significance of the Fraunhofer lines in the solar spectrum, thus laying the foundations of solar and stellar chemistry. The application of the spectroscope to analytical chemistry almost immediately resulted in his discovery of cœsium and rubidium.

• Bunsen worked on problems of chemical geology, and made a long series of analyses of volcanic products.

• With [Leon] Schischkoff, he examined, in 1857, the products of fired gunpowder.
  • Note: refer to Chemical Theory of Gunpowder (1857).

• He effected many improvements in analytical chemistry; devised the iodiometric method of volumetric analysis, and systematised the processes of water analysis.

• [H]e invented the gas-burner... with which his name is inseparably associated, and which has been of inestimable service to operative chemistry and in the arts.

• Bunsen was no theorist, and purely speculative questions had little or no interest for him.

• [H]e was a great teacher, and made the chemical school of Heidelberg no less famous than the schools of Giessen and Gottingen.

• Thorpe's observation... that "Organic chemistry has been largely developed by the discovery from time to time of special reagents and special types of reactions which have shown themselves to be capable of extensive application" continues to be true to this day.
  • J. M. Smallheer (2015) on the History of Chemistry, Volume II. From 1850-1910.

• Chemistry
• Historical View of the Progress of Chemistry by Humphry Davy
• History of chemistry
• History of science
• Organic chemistry

• Archive.org public domain books:
  • History of Chemistry Vol. I. From the Earliest Times to the Middle of the Nineteenth Century.
  • History of Chemistry Vol. II. From 1850 to 1910.

• Librivox.org public domain audiobooks:
  • History of Chemistry, Volume II. From 1850-1910 Sir Thomas Edward Thorpe (1845-1925) Read by: J. M. Smallheer.