[<< wikiquote] A History of Chemistry from the Earliest Times
A History of Chemistry from the Earliest Times (1920) was originally published as A History of Chemistry from the Earliest Times till the Present Day (1913). It is a work by chemist and professor James Campbell Brown, who taught at the Liverpool Royal Infirmary School of Medicine, University of Liverpool. He is best known for this history of chemistry. The work was completed, post-mortem, from the notes used by Professor Brown to deliver his lectures on the History of Chemistry. Those notes were consolidated and edited by Henry H. Brown, Professor Brown's cousin, who then published the book in two parts: Part. I. Ancient History, containing chapters 1-16, and Part II. Modern History, chapters 17-49.

== Quotes ==

=== Preface ===
The late Dr. Campbell Brown was accustomed, as part of his Chemical Course at Liverpool University, to deliver a series of Lectures on the History of Chemistry. These lectures were to him a labour of love, and were prepared after much research... It was his intention... to revise the lectures and to put them into shape for publication. But death put a sudden term to his labours... and the lectures were left in the form of manuscript notes, more or less complete, but not in that perfect shape which Dr. Campbell Brown would have wished... to be published.Mrs. Campbell Brown and the friends of the Author considered that it would be matter for deep regret if his... History were not carried into effect, and... made available to students and others interested in the subject.[I]t seemed good to Mrs. Campbell Brown to entrust the writer with the duty of editing... and passing the work through the press.[The editor] has endeavoured to present the substance of the lectures as nearly as possible in the shape in which Dr. Campbell Brown used to deliver them, subject to... changing them... to the form of a book... [I]t may be that in some instances the notes of Dr. Campbell Brown have been misunderstood. ...[T]he Editor, knowing the extreme accuracy of the Professor, requests that such slips may be attributed, not to the Author, but to himself.

=== Biographical Note ===
James Campbell Brown was born at Aberdeen, on January 31st, 1843. His father... soon removed to London as principal partner of the Bow Common Alum Works.[I]n 1863 he proceeded to the Royal College of Chemistry at London, where he studied under Tyndall and Hofmann, at the same time matriculating at London University. ...in 1870... obtaining the degree of Doctor of Science.With a elear perception of whatever object he had for the time being set before him, with indomitable courage to fight against a delicate constitution and indifferent health, and with a determination which would be satisfied with no half-measures, but would insist that whatever was done should be rightly done, he was a true representative of [his] family...One of my earliest recollections of my cousin, who was my senior by thirteen years, is of wandering with him in a field searching for a bulbous crowfoot... [A]t a later date it was on his initiative, and with his assistance and encouragement, that I began the amateur study of chemistry from which I acquired a knowledge of its practice and principles sufficient to enable me to undertake the editing of the present work.Educational and scientific matters... provided for him a field of usefulness in which he was occupied for the greater part of his life, and to which he devoted all his gifts of organisation, hard work, and self-denial.In the new College he occupied the Chair of Chemistry, and found a fresh field of work in organising the duties of the Chair, and planning and equipping the classrooms and laboratories which were essential for their performance. The Chemical Laboratories were built in 1884 and extended two years later, while in 1896-7 the Wilham Gossage Laboratory was opened and rooms were added for Metallurgy, Electro-Chemistry, and Gas Analysis. The whole forms one of the most perfect installations for the teaching of chemistry, which is to be found in this country.He was in 1872 appointed’Public Analyst for Liverpool under the Adulteration of Food Act, and received a similar appointment for Lancashire in 1875. ...In addition, he was analyst to the Water Committee for the City of Liverpool, and to all the Local Authorities in the administrative county of Lancashire, and was frequently consulted in reference to large schemes of public water supply, both at home and abroad.How his services were appreciated by those who were associated with him in the Water Undertaking, may be estimated from the following extract from the Report of Mr. Joseph Parry, the Water Engineer, for the year 1910:—"He was a rigid guardian of the purity of the supply, and it was an enormous advantage to the Corporation to have the professional assistance of one who had attained to such eminence and influence as a chemist."He was skilled in forensic chemistry, and was engaged in a number of criminal cases involving the use of poisons. His experience in the matter of arsenic poisoning was unique.He was one of the original members of the Society of Chemical Industry, and as the result of a long series of experiments in the analysis of soils and examination of tea-plants, devised a fertiliser for use in tea plantations in India. Where it was adopted, this fertiliser raised the tea production from 397 to 494 pounds per acre, and it is characteristic of him that he refused... pecuniary return from its very extensive use.His "Practical Chemistry" is now in its sixth edition.He made several ingenious inventions. An apparatus for the direct determination of the latent heat of evaporation was awarded two gold medals at the Franco-British Exhibition at London in 1908. ...[T]his apparatus was exhibited at the Japan-British Exhibition in 1910, and along with it another invention—an apparatus for fractional distillation of fats and fatty acids in the vacuum of the cathode light. Both of these exhibits were again shown in 1911 at the Coronation Exhibition in London.The University of Aberdeen in 1907 conferred upon him the Degree of Doctor of Laws. In 1908 he was elected Vice-President of the Chemical Society of London, an office which he held at the time of his death. The Council of the Institute of Civil Engineers awarded to him in 1904 the Mamby Premium for a paper on "Deposits in Pipes and other Channels conveying notable water." He was a member or an honorary member of numerous scientific bodies...He had suffered from an attack of influenza... [H]eart failure ensued and he died... March 14th, 1910. ...[H]e was called away without the trial of a lingering illness. He died in harness, for he was giving instructions to his secretary about examinations, and signing certificates, till within ten minutes of the end.I have failed in my purpose, if I have not made plain two points—his devotion to duty, and his thoroughness. He took life at a gallop; he never spared himself when duty was to be done; and he was not satisfied with any attainment short of absolute precision and completeness. In that single sentence his biography is comprised.

=== Ch. XI The Protest of Paracelsus ===

==== Paracelsus ====
The art of alchemy was now to receive an impulse in a new direction.In the hands of the fourteenth century alchemists and their immediate successors, its main object had become the discovery of that mysterious powder or elixir, which was to bring about universal perfection, to raise the baser metals to the perfect gold, and to endow human beings with eternal youth.At this stage a great, though erratic, genius appeared on the scene, and opened up a fresh channel, into which students of chemical science might thenceforth direct their energies.Paracelsus (1493—1541), who gave his name as Philippus Aureolus Theophrastus Paracelsus Bombastes ab Hohenheim, created in his day more stir than any other alchemist, for he shook the faith of the world in Galen and Avicenna, and was thus the means of introducing a new era.[A]lthough there is no reason to doubt that he was gifted with original genius... he was on the whole a vain and self-seeking quack, who neither understood the nature of chemical science, nor undertook any regular or successful investigation. But he condemned loudly and boldly all medical knowledge and all medical practitioners, except himself, and his own methods. By these means, and by some cures which he effected, partly by bold treatment, partly by good luck, he made such a reputation for himself that he freed the medical world from old trammels.He roused the mental energy of medical men by calling their attention to the importance of chemical medicines and chemical investigations, and in consequence, workers arose who studied the preparations and reactions of those metals which were most likely to be useful in medicine, and by their efforts the store of chemical knowledge was rapidly increased.His father, Wilhelm von Hohenheim, was a physician and taught him alchemy, astrology, and medicine.After a short period spent at the University of Basle, [Paracelsus] became a wandering scholar, practising medicine and picking up knowledge over the greater part of Europe, Egypt, and Tartary.He had little university training, but worked long and earnestly with the wealthy Sigismond Fuggerus of Schwartz, trying to make the philosopher’s stone.Loud advertisement of the successful cures he had wrought by the use of mercury and opium raised him to such a pitch of fame that the magistrates of Basle in 1526 appointed him to the Chair of Medicine in that University.At his first lecture he ostentatiously burned the works of Galen and Avicenna, the great medical authorities of the age. In this spirit he lectured for two years, but his vanity and bombast disgusted and drove away his students, and his greed made him quarrel with the magistrates over his fees. In the end he suddenly quitted the town, and resumed his wandering life through Alsace and Germany.During the latter part of his career he effected many cures, the reputation of which concealed his many failures, but his private life was disfigured by intemperance, which he indulged in the lowest company.Finally, he announced that he had discovered the Elixir Vitæ, and could extend human life for an indefinite term. [H]owever, he was unable to conform to the maxim "physician, heal thyself," for he was seized with a fever and died at Salzburg in 1541, at the early age of 48. His property was bequeathed to the poor.Paracelsus did little by actual discovery to advance either science or medicine.His great work was effecting a breach with tradition, and setting physicians and alchemists free from the bondage in which they were held by convention.He borrowed his medical treatment from others—barber-surgeons, old women and quacks—and his fearless nature made him employ the powerful and dangerous medicines prepared from mercury, opium, and antimony more boldly than any before him had ventured to do.His alchemical doctrine, that everything consisted of three elements—mercury, sulphur, and salt—is adapted from old authors, but he was the first to use the word "alcahest" to indicate the universal menstruum or solvent, which at that time was a special object of research. He describes this liquor, alcahest, as having great power over the liver, comforting and confirming it, and preserving it from dropsy and other diseases that take their origin within it. ...Unhappily, he does not give precise directions for the preparation of this invaluable remedy.The great debt which chemistry owes Paracelsus is the influence... in discarding the ideas of the ancients, and even of the more modern alchemists, and in teaching that the object of chemistry was not to make gold but to ameliorate disease.The art of making drugs was one of the original branches of alchemy, but for many centuries this had been obscured by endeavours to effect the transmutation of metals. Paracelsus reinstated it in its prominent position.He used preparations not only of antimony, but of mercury, lead, iron, blue vitriol, and (for external use) arsenic. He said that the most energetic poisons might become precious medicines, and endeavoured to concentrate in essences, extracts, and mixtures the active principles of various drugs.He arranged the several parts of man, his own universal elements, and the Aristotelian elements in triplets, thus :—Having adopted the Cabala and its doctrines, he was grossly pantheistic.As a rule his writings are full of mysticism, although there are a few grains of wheat among the chaff.He repudiates the view of Galen that fire is dry and hot, air moist and hot, earth dry and cold, and water moist and cold. He says that each of these elements is capable of admitting all qualities, so that there is a dry water and a cold fire.[According to Paracelsus,] [t]here is in the stomach a demon named Archæus, who presides over the chemical operations which take place in that organ, changing bread into blood, and separating the poisonous from the nutritive. Tartar is the leading principle of the maladies which arise from the thickening of the humours. Stone in the abdominal organs is only part of it, and as tartar is deposited in wine casks, so tartar is deposited on the teeth. When tartar is increased by certain kinds of food, renal calculi are engendered. In this connection he thought it necessary to subject urine to chemical analysis.All remedies, according to Paracelsus, are subject to the will of the stars and are directed by them, but chemistry is indispensable in the preparation of medicines. After his time the old disgusting decoctions gave place to tinctures, essences, and extracts. He even recommended quintessences, and described how they were to be made.[H]e ascertained that alum contains an earth united to an acid.He mentions metallic arsenic, zinc and bismuth, but did not regard them as true metals, to which he considered malleability and ductility as essential characters.[H]is reputation as a chemist depends not so much upon discoveries made, as on the importance which he attached to a knowledge of the science.In consequence of his teaching chemistry became an indispensable part of the education of a medical man, and it was perceived that the true object of the science was not the discovery of the philosopher’s stone, but the preparation of new medicines. He thus introduced the next period in the history of chemistry, when many medicinal and other substances were discovered in the laboratories of the chemical physicians, or Iatrochemists...

==== Gerhardt Dorn ====
As might be expected the protest of Paracelsus against ancient tradition led to a vast amount of discussion among contemporary alchemists. One of these named Gerhardt Dorn (circa 1550—1600), a pupil of Paracelsus, in his Clavis Totius Philosophiae Chymisticae (1561), Artificii Chymistici {circa 1568), and In Aurorum Paracelsi (1583) attempted to explain and comment upon his master. ...[H]e only rendered obscurity more obscure.

==== Thomas Erastus ====
Thomas Erastus (1523-83)... adopted the reasoning of scholastic philosophy and thus weakened the force of his attack, but he pointed out many contradictions in the writings of Paracelsus and his followers, denied the existence of the philosopher's stone, and combated the idea that mercury, sulphur, and salt are the elements of living bodies.He charged Paracelsus with bad faith.Erastus... wrote an apology for hermetic science, and treatises on the philosopher's stone and the triple preparation of gold.

==== Leonhardt Thurneysser zum Thurn ====
Leonhardt Thurneisser or Thurneysser zum Thurn (1530-96), a native of Basle and a friend and pupil of Paracelsus... had not the penetration of his master, and lived most of his life by his wits.His chief experimental work was a very incomplete investigation of the residues got by evaporating mineral waters.He wrote many books, of which may be named Quinta Essentia (1574) and Magna Alchymia (1583).His father was a goldsmith, who, having need of money, sold a quantity of gilded lead as gold. This was the son’s introduction to alchemy, as his father understood the art.After a visit to Germany, France, England, and the Scottish lead mines, Thurneysser started mining and sulphur-extracting in 1558...[L]ater... he studied under Paracelsus, and so far associated himself with the Paracelsian system that he acquired a great reputation for a time, which was heightened by his curing the wife of the Elector of Brandenburg. He was thereupon made court physician, and amassed a considerable fortune by medical practice with tincture of gold and similar medicines, but was exposed by Gaspard Hoffmann, lost his repute, and fled to Italy.His last years were devoted to transmutation of metals, and he died at Cologne.His character is well summed up by Ferguson: "He was endowed with quickness and a powerful memory, but he tried to pass as a man of science, a learned physician, and an accurate scholar, when in reality he was a man of action with a gift for organising and commercial advertising. At the present day he might have been a successful manufacturing chemist, able to turn his raw material into gold without the red elixir."

==== Giovanni Agostino Pantheo ====
Pantheus was an instance of a churchman devoting himself to alchemy. His full name was Giovanni Agostino Pantheo (circa 1510-60), and he was a priest at Venice.[H]is books—Ars et Theoria Transnmutationis Metallicae cum Voarchadumia (1550) and Voarchadumia contra Alchimiam (1530). He opposed the spurious alchemy current in his day, and treated of the purification and assaying of gold, the manufacture of white lead, and the preparation of an alloy used for making mirrors.

==== Bernardus Georgius Penotus ====
Bernardus Georgius Penotus (1520—1618)... studied at Basle, and first admired Paracelsus and then abused him as a plagiarist.He wrote several books dealing with medicine and chemistry, of no great importance, squandered his means in the search for the philosopher’s stone, and died in the poor-house...His most valuable contribution to philosophy was the bitter remark that if he had an enemy whom he dared not attack by force, but yet to whom he wished to do the greatest possible injury, he would urge him by every means in his power to study alchemy.

==== Rosicrucian Order ====
[A] a mysterious body, the Rosicrucian Order... seems to have owed its origin to a determination to uphold the ancient alchemy in opposition to Paracelsus and all innovators.The cult is involved in mystery and doubt, and has for centuries exercised an attraction, and retained a prestige, of which it was hardly worthy.The extreme caution which was observed by its members in preserving their secrets, if they had any, and the unintelligible symbolism in which they contrived in their published writings to wrap up their meaning, have combined to render the study of Rosicrucianism extremely difficult and confusing.The Rosicrucians seem to have existed for about one hundred years, practically coeval with the seventeenth century.They devoted themselves to the study of science, astrology, necromancy, and, it is said, some of the most debasing forms of Oriental superstition.Their energy was due to the impulse imparted to human thought by the three great events of the Middle Ages; the discovery of America, the invention of printing, and the reformation of religion.To them the Cabala was the touchstone of wisdom.To them the Cabala was the touchstone of wisdom. They mixed the spiritual with the material, aiming at the perfection of the human body and soul, as well as at the transmutation of the baser metals into gold.Incidentally, they discovered scientific facts, but directly they sought to impress the truths that men ought to subordinate their appetites and desires to nobler aspirations, and that by the subjugation of our lower nature we actually prolong our lives.

=== Ch. XIII The Philosophy of the Alchemists ===
[T]he writings and labours of the alchemists were both extensive and important. ...[T]heir studies, although misdirected, were not... haphazard. The alchemists had a definite, and... logical, system of philosophy... [T]hey recognised—(1) the unity of matter; (2) the three principles—philosophical mercury, sulphur, and salt; (3) the four elements—fire, air, water, and earth; and (4) the seven metals—gold, silver, mercury, copper, iron, tin, and lead.

==== The Unity of Matter ====
This was the fundamental theory of alchemy, and goes back to remote ages. [T]he smaragdite tablet attributed to Hermes Trismegistus [states] "As all things were produced by the one word of one Being, so all things were produced from this one thing by adaptation," and we again find it in the "one is all" of the Chrysopoeia of Cleopatra...The alchemists held that matter is one, but can take a variety of forms, and under these different forms can be combined and re-combined ad infinitum.The original matter, or prima materia, was called by various names—universal substance, seed, chaos. Although  matter changes its form, it cannot be destroyed.As Hermes is alleged to have said. "Nothing in the world dies, but all things pass and change."In its nature the prima materia was assumed to be a liquid, containing everything in posse, but nothing in esse.

==== The Three Principles ====
All metals and minerals consist of certain principles. These were at first called "mercury" and "sulphur," not the ordinary substances... but a philosophical mercury and a philosophical sulphur.At a later period the alchemists added a philosophical salt, or a philosophical arsenic, but they never ascribed to these the importance they attached to the other two principles.Traces of these ancient conceptions are still to be recognised in the word "quick-silver," that is living silver, a literal translation of argentum vivum. A term "quick-sulphur" (sulphur vivum) was also in use, but it has long since disappeared.The mercury of a metal... represented its lustre, volatility, fusibility, and malleability; the sulphur of the metal, its colour, combustibility, affinity, and hardness.The salt of the metal was merely a means of union between the mercury and the sulphur, just as the vital spirit in man unites soul and body. It was doubtless devised to impart a triple form to the idea, in conformity  with the method of the theological schoolmen.Mercury, sulphur, and salt were not three matters, but one, derived from the prima materia.[W]hen an alchemist converted a metal into its oxide, or, as they expressed it, "made a calx" of it, he thought he had volatilised its mercury and fixed its sulphur. When he distilled ordinary mercury and found a solid residue in the alembic, he called it the "sulphur" of mercury; when he found a sublimed product in the receiver (mercury bichloride), he termed it the "mercury" of mercury or "corrosive sublimate."The more logical mind of Artephius Longaevus introduced a modification of this theory. He distinguished two properties in a metal—the visible and the occult. The former, comprehending its colour, lustre, extension, and other properties visible to the eye, he called its "sulphur"; the latter, comprehending its fusibility, malleability, volatility, and other properties not visible until after... special treatment, he  called its "mercury."Practically... there was little difference in the application of these diverse theories regarding the three principles.

==== The Four Elements ====
Aristotle... taught that all things consisted of four elements, or rather four elemental properties:—1. Fire, the property of dryness and heat;2. Air, the property of wetness and heat, or of gaseousness;3. Water, the property of wetness and cold;4. Earth, the property of dryness and cold, or of solidity.The alchemists adopted these four states of matter, and sought them in all substances. Everything hot was called "fire"; cold and subtle, "air"; moist and fluid, "water"; or dry and solid, "earth."But, as heat changes liquids to vapour, and consumes solids, they reduced the number of visible elements to two—earth and water, which contained within themselves the invisible elements, fire and air.They were thus able to apply the conception of the three principles to that of the four elements. Earth corresponded to philosophical sulphur, and water to philosophical mercury. Later, when they conceived philosophical salt, they devised a fifth element called "quintessence" or "ether." which corresponded to the third principle. Thus, if an alchemist distilled wood and obtained an inflammable gas, a liquid oil and a solid  residue, he said that he had decomposed the wood into its elements—fire, water, and earth.

==== The Seven Metals ====
[T]he Chaldean star-gazers of Harran came to fix the number of metals at seven, and to associate them with the sun, moon, and five planets in the following manner:—Gold, corresponding to the sun.Silver, corresponding to the moon.Mercury, corresponding to the planet Mercury.Copper, corresponding to the planet Venus.Iron, corresponding to the planet Mars.Tin. corresponding to the planet Jupiter.Lead, corresponding to the planet Saturn.Each metal acted under the influence of the planet with which it was associated...[T]hey regarded gold and silver as being perfect, because they were unalterable... The other five were deemed imperfect, as each could be formed into a calx or oxide, was readily attacked by acids, and could be consumed by fire; but they deemed it possible to purify and modify the imperfect metals, so as to transmute them into the perfect.The seven metals were... derived like other substances from the prima materia or universal substance. They were the same in essence and differed only in form.The sulphur of a metal was its active principle; the mercury its passive; the salt was the link which united the other two.The sulphur, the property of dryness and heat, ultimately overcame the mercury, the property of wetness and cold, and thus changes were effected. ...[S]ulphur was the father, mercury the mother, and metals were conceived between them. In this expression the philosophical principles are meant, not the ordinary substances called sulphur and mercury.[A]lchemists accounted for the diversity of metals by five causes:—1. Variation in the proportion of the principles, mercury and sulphur.2. Variation in the purity of these principles.3. Variation in the duration of the period of concoction to which the compound was subjected in the bowels of the earth.4. Variation in planetary influences.5. Variation in accidental influences.Nature always sought to attain perfection, but was checked by these diverse causes, and instead of producing the perfect metals, gold and silver, produced imperfect metals, mercury, copper, iron, tin, or lead.The later alchemists, who were mostly astrologers as well, laid special stress upon the influence of the heavenly bodies. ...Paracelsus even pretended to be able to calculate when and how this planetary influence  took effect.In the fifteenth and sixteenth centuries alchemy was affected by two external systems, magic and religion, both to its detriment. To astrology the alchemists added necromancy and the Cabala. The latter had really no connection with alchemy. It was a purely speculative system of numbers.At a still later date it was argued that exact and natural sciences proceed by induction and deduction, and occult and spiritual sciences by analogy. Following out this line of thought the alchemists produced the following remarkable trilogy:—Each of these was a trinity in unity, and a unity in trinity. In each world was a distinct design,—in the material, the perfection of the metals; in the human, the perfection of the soul; in the divine, the contemplation of the Deity in His splendour.These mystic alchemists interpreted the three principles in their own fashion. Mercury, the passive and female principle, was matter; sulphur, the active and male principle, was force; and salt, the middle term in the proposition, was movement, which applied force to matter. Or, expressed in another shape, mercury was the subject: sulphur, the cause; and salt, the effect. Symbolically, the theory was represented by an equilateral triangle, in one angle of which was the sign of sulphur or force; in the second, the sign of mercury or matter; and in the third, the sign of salt or movement.[T]he philosophy of the alchemists... when fully considered... is by no means despicable. The knowledge which was at that period available did not permit of the practical application of this philosophy, and the sages did not rightly understand their own theories. Yet... while there is much that seems absurd and nonsensical, there is much which is not inconsistent with recent researches and discoveries of science.

=== Ch. XVII The Iatrochemists ===
(From 1500 A.D. till 1700 A.D) 1. Basil Valentine to Oswald CrollThe Modern History of Chemistry may be said to have begun when the alchemists... applied their minds to the search for knowledge instead of the search for gold.The peculiarity of the Iatrochemical Period is the tendency of chemistry towards investigating and producing new medicinal preparations by chemical means, and forming other chemical compounds in the search for new medicines, in place of a tendency towards searching for the philosopher's stone, which was the peculiarity of the Alchemical Period.The iatrochemists, chemist-physicians, or chemist-apothecaries, devoted themselves mainly to the attempt to discover the Elixir Vitœ or universal medicine, a quest as hopeless as that of their predecessors, yet they did not altogether give up the older quest, and the search for the red elixir or philosopher's stone continued to engage the attention of chemists during the whole Iatrochemical Period, which endured from the first quarter  of the sixteenth century till the middle of the seventeenth, or a little later.[P]eculiarities assigned to each period are not to be regarded as being anything more than general characteristics. Thus, alchemical ideas extended far down into the Iatrochemical Period, so that we find Van Helmont declaring that he believed in the transmutation of metals, and that he possessed a small portion of the  philosopher's stone. This attitude was characteristic of those chemist-physicians of the seventeenth century who practised medicine according to the old traditions.On the other hand, those who followed Roger Bacon in the study of theoretical chemistry for its own sake, or who made technical applications of it, tended rather in the direction of our modern views, even prior to the close of what we term for convenience the Iatrochemical Period.The iatrochemists carried to excess their efforts to give an explanation of everything which happened in the human body and in Nature; but their explanations were fanciful and founded either upon complete ignorance or entire neglect of facts. Their contributions to the philosophy of chemistry were meagre; their additions to our  knowledge were the fruits of their practical research.[T]he period is in marked contrast to the next, the Phlogiston Period, which is memorable for the development  of a rational theory of chemistry, which, although wrong, is not so far wrong as may appear... at first sight...[S]everal men whom we have included in the Alchemical Period were iatrochemists as well as alchemists. Of these we may mention Paracelsus... Erastus... who although he opposed Paracelsus was an advocate of chemical medicines, Thurneysser... Ulstadt... Sir Kenelm Digby... and Hermann Conring...

==== Basil Valentine ====
[W]e mention... one who might have been included among the alchemists—Basil Valentine (circa 1394—1450). We... deferred consideration... partly because his reputation rests upon his advocacy of the medicinal virtues of antimony, and partly because he is a mythical personage, and there is reason to believe that the writings attributed to him are the work of an anonymous author of the Iatrochemical Period.His biography is made up of several more or less improbable legends.[T]he works were not published till 1602, or nearly two hundred years after Valentine's death, but whether they were only then discovered, or... only then written... is now impossible to answer with confidence.About two dozen books stand in the name of Basil Valentine. Of these the most important is Currus Triumphalus Antimonii (The Triumphal Chariot of Antimony), and one of the best English editions is the translation of the work and of the notes by Theodore Kirkringuis or Kerckringuis, made by Edward Russell, in 1678. It is an excellent book, far too good... for the time of its reputed author. In clear and precise terms it sets down all that was known about antimony prior to the discoveries of the nineteenth century.The writer of these books, whoever he was, had a wide knowledge of chemical compounds. He understood the preparation of hydrochloric acid, which he called spirit of salt, by the distillation of common salt with sulphuric acid. He knew arsenic and its sulphide, realgar; zinc in its compound, if not its metallic, state; bismuth, which he sometimes termed marcasite; the red oxide, nitrate, and bichloride of mercury (corrosive sublimate); antimony and its compounds; the acetate, yellow oxide, and white carbonate of lead; and of the Iron salts, ferrous sulphate (green vitriol) and the double chloride of iron and ammonium. He obtained metallic mercury by distilling corrosive sublimate with chalk. He discovered fulminating gold. He precipitated metallic solutions by alkali; copper by iron; and gold by mercury. Lastly, he experimented with spirits of wine, which he combined with nitric or hydrochloric acids, and used for dissolving the caustic alkalis.[H]e was as bitter against the physicians of his day as Paracelsus. He believed that there is an analogy between the purification of gold and the cure of disease, and maintained that antimony is sovereign for both.He asserted that the metals are composed of the mercury and sulphur of the philosophers, to which he added philosophical salt. The philosopher's stone, he said, is composed of the same materials.[H]is works do not merit the deference they received, and... the knowledge imputed to him is almost certainly  not his, but belongs to a far later period... [R]eceive with caution all that is said about Basil Valentine in text-books and histories.

==== Francis Anthony ====
Francis Anthony or Antonio (1550—1623) was an unlicensed practitioner, who advocated chemical medicines, and sold a panacea aurea after the fashion of Paracelsus.He strongly maintained the virtues of aurum potabile (liquid gold), and wrote a book entitled Medicinae Chymicae et Veri Potabilis Auri Assertio (1610). Another tract, De Lapide philosophorum et Lapide Rebis, related to the older alchemy. ...[I]n alchemical symbolism "Rebis" was the name given to the hermaphrodite figure representing the union of the great philosophical principles, sulphur and mercury, in the operation of making the philosopher's stone...It is refreshing, among the many vain theorists and dreamers of those days, to come upon a man who was a theorist... but also an acute observer and accurate experimenter.

==== Andreas Libavius ====
Andreas Libavius (1540—1610) was one of the pioneers of chemical science, and the first author who wrote a really valuable text-book of chemistry.As a physician he was an unflinching opponent of Paracelsus; as a chemist he was an earnest seeker after truth.He was so far the child of his age that he believed in the possibility of the transmutation of metals and in the virtue of aurum potabile, but he was so far in advance of it that he was able to distinguish between the mystical and the practical, and to make discoveries which enriched the science.Much of his time was wasted in useless controversy. He thought it his duty to expose the quackery of his contemporaries, and as the quacks were numerous and vindictive, the struggle was continuous and bitter.His System of Chemistry, published... in folio in 1585, and in quarto in 1597, has the... title: "Alchymia e Dispersis passim Optimorum Auctorum..." was for long the leading textbook on the science, and contained a collection of all the chemical facts then known. He also wrote Ars Probandi Mineralia (1597), De Judicio Aquarum Mineralium (1597), Praxis Alchymiae (1604), Alchymia Triumphans (1607). They were ultimately collected as Opera Omnia Medico-Chemica.Libavius was mainly interested in the preparation of chemical medicines, but some passages in his writings bear on the transmutation of metals.He observed that the fumes of sulphur blacken white lead; he purified cinnabar by means of arsenic and lead oxide; he made artificial rubies and other precious stones by tinting glass with metallic oxides; he described fluor spar as a flux for metals and their oxides; he oxidised sulphur with nitric acid; he knew that alcohol is  obtained by distilling the fermented juice of sweet fruits; he proved that the acid extracted from alum and from ferrous sulphate (green vitriol) is the same as that obtained by burning sulphur with saltpetre, that is to say, it is sulphuric acid; and he discovered tin tetrachloride (stannic chloride), which is sometimes called Liquor fumans Libavii. It is a truly remarkable record of practical work, considering the age in which Libavius  lived.

==== Angelo Sala ====
One of the most original thinkers of his day was Angelo or Angelus Sala (1575—1640).His Opera Medico-Chemica were published in 1647. He scouted the idea of the philosopher's stone, or of a universal medicine, and rejected aurum potabile for medicinal purposes. He administered gold only in the form of the fulminate.Sala showed that sal ammoniac is obtained by treating ammonium carbonate with hydrochloric acid; he described ammonia in wonderfully clear terms; he observed the formation of nitric acid by the action of sulphuric acid upon saltpetre; and he recognised that in the deposition of copper upon iron, when the latter is dipped in a solution of cupric sulphate (blue vitriol), there is no change of metal, but that the blue vitriol already contained copper.In the words of Conring.... he was "primus chemicorum qui desiniit ineptire" (the first chemist who ceased from trifling).Whether as a critic of the old theories, or as an exponent of the new, Sala merits a distinguished place amongst the founders of chemistry.

==== Jan Baptist van Helmont ====
[T]he greatest name of this period is... Van Helmont.Paracelsus had discarded the disgusting decoctions of Galen and introduced chemical medicines, while Libavius and Sala had dismissed the fanatical conceptions which disfigured and almost nullified the teachings of both Paracelsians and Rosicrucians, but chemists still adhered either to the Aristotelian doctrine of the four elements, or to the later theory of the three principles (mercury, sulphur, and salt). John Baptist van Helmont  (1577—1644) was the first to deny these propositions, and to begin a revolution in the philosophy of chemistry.Continuing his philosophical studies under the auspices of the Jesuits, he was taught necromancy, but was soon disappointed with such useless learning. He then turned to mysticism, reading the works of Thomas à Kempis  and John Tauler. ...[H]e resigned his titles, and gave up his  property to his sister.Desiring now to practise medicine, he read Hippocrates and Galen, but detected the futility of their methods of treatment. This led him to become a disciple of Paracelsus, but having much greater knowledge than that writer, he speedily discovered the ignorance and egotism which mar his writings.In 1599 he took his degree as Doctor of Medicine, and for a time travelled and practised his profession in various countries. At last he married... and passed the closing years of his life on his own estates at Vilvorde, chiefly in his laboratory.Van Helmont absolutely discarded the doctrines of Aristotle and Paracelsus in regard to the four elements and  the three principles. He denied the elemental character of fire, air, and earth. He disputed the material existence of fire, and asserted that earth cannot be an element, because it can be converted into liquid.He admitted the elemental nature of water, which he deemed the fundamental principle of everything that exists. All metals and even rocks, he affirmed, may be resolved into water, and from water all animal and vegetable substances may be produced. The former proposition he based upon the fact that fish live in water; the latter he proved by a curious, but faulty, experiment.He took a willow weighing five pounds, and planted it in two hundred pounds’ weight of earth carefully dried in an oven. All dust was excluded, and the plant was frequently watered. At the end of five years he weighed the plant. Its weight was one hundred and sixty-nine pounds, an increase of one hundred and sixty-four. He again dried the earth, and weighed it, when he ascertained that it had lost only two ounces. Hence, he concluded that the increase of one hundred and sixty-four pounds in the weight of the willow was derived from water alone. He was not aware that in addition to the water, the plant had absorbed a great store of carbon from the carbonic acid gas (carbon dioxide) existing in the air.Van Helmont was the first to perceive that when a metal is dissolved in an acid it is not destroyed, but may be recovered from the solution in the metallic state by the use of suitable means.[H]is outstanding discovery was the discrimination of various kinds of air, which he thus proved to be no elementary substance. In this connection he introduced the term "gas." Of these gases he mentions several, but the most important were "gas silvestre" (i.e., the gas that is wild and dwells in out-of-the-way places) and "gas pingue."Gas silvestre was evolved from alcoholic liquor during fermentation, from burning charcoal, from marble or {{w|chalk} when acidulated, and from the Grotto del Cane near Naples. It was, in fact, carbonic acid gas, or carbon dioxide (CO2).[T]his discovery... was entirely forgotten by chemists, and... carbonic acid gas was rediscovered by Dr. Black in the middle of the eighteenth century under the name of "fixed air."Gas pingue was an inflammable air evolved from dung, and was probably impure gaseous ammonia.He held strange notions respecting the vital functions. From his sensations on swallowing aconite he thought that the stomach was the seat of the sentient soul, which he named Archeus. ...[H]e founded his physiological system on the operation of Archeus and of various ferments, all mainly imaginary.Van Helmont believed in the philosopher’s stone and in transmutation, but did not waste much time upon that part of alchemy. He asserted that he had actually witnessed the transmutation of a base metal into gold...His chief aim, however, was the discovery of the alcahest or universal solvent, another of the alchemical problems, and in this line he was followed by Glauber... It seems to have been thought that the alcahest would be a universal medicine as well as solvent. It is a curious reflection that it never seems to have occurred to Van Helmont and others to consider how they were to retain the alcahest, when they found it. ...[I]t would dissolve the vessel ...so would be lost as soon as found!The writings of Van Helmont were collected in 1648 under the title of Ortus Medicinae vel Opera et Opuscula Omnia.All honour is due to his name. In addition to his great discovery of the diversity of gases, and the distinction between gas and vapour, he was the first to point out the imperative necessity for the use of the balance in chemical operations, and to adopt the melting point of ice and the boiling point of water as standards for the measurement of temperature. It is in his writings that the term "saturation" in its chemical sense first occurs. Altogether he was a great chemist, undoubtedly the greatest prior to Lavoisier.

==== Daniel Sennert ====
Daniel Sennert [circa 1575—1625) is... notable as a professor of medicine at Wittenberg, who devoted himself to the advocacy of chemical medicines.He was held... by the erroneous doctrines of Paracelsus, especially... the three principles, but he did good service to chemistry by protesting against the possibility of a universal medicine.His chief work was Epitome Naturalis Scientiae, which was published at Oxford in 1664.

==== Oswald Croll ====
Oswald Croll (1580—1609)... won distinction as a pharmacist.His Basilica Chemica, published at Frankfort in 1608... is a treatise of some  value. The English edition  was entitled "Philosophy Reformed and Improved in Four Profound Tractates" (1657).He discovered, or brought into use, a number of new medicines: for example, volatile salt of amber (succinic acid); potassium sulphate; antimonic acid; calomel; fused silver chloride [luna cornea), and silver chloride prepared by precipitation. Of course, he did not use the modern names of these substances, which are adopted here...Croll was a practical chemist, rather than a theorist, although the Basilica contains a critical study of the  Paracelsian doctrines, and discusses at length both pharmacy and therapeutics, as they were understood in his day.

=== Ch. XVIII The Iatrochemists ===
 (From 1500 a.d. till 1700 A.D.) 2. John Rudolph Glauber to Nicholas Lemery

==== John Rudolph Glauber ====
Much of his time was wasted in writing polemical tracts against those who still followed Galen. His anger was specially kindled against one Earner, who had worked in his laboratory, to whom he had communicated secrets, and who had not only broken his promise not to divulge these, but had boasted of them as his own discovery, and added insult to injury by decrying the skill of Glauber.The collected works of Glauber were translated into English in 1689 by Christopher Packe.
Source: The works of the highly experienced and famous chymist, John Rudolph Glauber (1689)Glauber was an alchemist and a believer in the universal medicine, but he was also an iatrochemist, and applied chemical processes to the improvement of both medicine and art.His first treatise related to philosophical furnaces, Furni Novi Philosophici (1648)... showed how he made chemical preparations with these; for example, muriatic acid by distilling salt (sodium chloride), ferrous sulphate (green vitriol), and alum.The name "muriatic" acid, derived from "muria," brine, was invented by him. He made solutions of metals in this acid, calling them "oils" of the metals. The chlorides of gold, iron, [[w:Mercury chloride|mercury]], and antimony, thus prepared, he praised as medicines.Sulphuric acid he made by distilling green vitriol (ferrous sulphate), and nitric acid by distilling nitre (potassium nitrate), and alum (double sulphate of potassium and aluminium). Fulminating gold he prepared, but said it was of little use as a medicine.In... "The Mineral Work" he explains how to separate gold from clay and other earthy substances by means of spirit of salt (hydrochloric acid). He further describes a panacea or universal antimonial medicine, consisting of a solution of oxide of antimony in pyro-tartaric acid, which he eulogised as being specially good for cutaneous eruptions.The salt which still bears his name, sodium sulphate, and which he called Sal Mirabile, is the subject of a long disquisition in his "Miraculum Mundi." We recognise it as a useful purgative, but Glauber maintained that it was a universal medicine and partook of the nature of the alcahest.Secret sal ammoniac (ammonium sulphate) is recommended in the "Spagyrical Pharmacopoeia or Dispensatory" as a substance used by Paracelsus and as the alcahest of Van Helmont. He gives a clear description of its preparation and of its conversion into ordinary sal ammoniac (ammonium chloride) by distillation or sublimation with common salt (sodium chloride).He knew ammonium nitrate, which he termed "nitrum flammans."In 1648 he demonstrated the possibility of making blue vitriol (copper sulphate) by boiling copper with sulphuric acid.He prepared a vinegar, which he called acetum lignorum, by the destructive distillation of wood. It was what we now term pyroligneous acid. He said that by re-distillation it could be made as "virtuous" as acetum vini, or "common wine vinegar," a fact not unknown to those artful persons of the present day who adulterate malt vinegar. The preservative effect of wood tar did not escape his observation.Glauber was a keen observer, a persevering experimenter, and an original genius, and he had the modesty of genius, for he says... "Nevertheless, I easily persuade myself that this discourse of mine will not be credited by many, which I cannot help. It contenteth me that I have written the truth, and lighted a candle to my neighbour."

==== Werner Rolfinck ====
Werner or Guerner Rolfinck (1599—1673)... has been called "the first professor of chemistry in Germany."Alchemy he determinedly opposed, and his treatise "Chymia in Artis Formam Eedacta" (1661) methodised the science, and according to Stahl (1766), "brought chemistry into shape, deduced its operations from causes conformed to Nature and reason, and laid a foundation on which many subsequently built."So keen an anatomist was he that the verb "to Rolfinck" became a popular equivalent for "to dissect"...

==== Christopher A. Baldwin ====
The author of the book Aurum Superius (1675), Christopher A. Baldwin (1600—1682) is memorable for a single discovery. He prepared a hygroscopic salt by treating chalk with nitric acid. This substance took up water from the atmosphere, which he distilled off, and sold under the name of "Spiritus Mundi" using the title of an old alchemic conception. The calcined salt (anhydrous calcium nitrate), being phosphorescent in the dark, he named "phosphorus." It thus became known as Baldwin’s Phosphorus, and created much interest, ultimately leading to the researches which enabled Brandt and Kunckel to discover the element which we now call "phosphorus."

==== Franciscus Sylvius ====
Francois de la Boe or Bois, in Latin Franciscus Sylvius (1614—1672), was... [a] disciple of Van Helmont and Descartes... led to the study of those chemical compounds which we now term "salts."The first chemical laboratory in Europe was on his persuasion erected by the University of Leyden, where he became Professor of the Theory and Practice of Chemistry.He was one of the most eminent iatrochemists, was the first to prove the presence of volatile alkali in plants, and regarded all phenomena from a purely chemical standpoint, but he had wild notions of physiology.While he agreed with Van Helmont in attributing many of the operations of the human body to fermentation, he entertained a totally different idea of what fermentation was, and sometimes used the word "effervescence" to denote the process.Van Helmont recognised the acid of the gastric juice and the alkali of bile, but Sylvius appreciated the importance of the salivary secretion and the pancreatic juice. Many of the digestive processes were, he maintained, due to the saliva swallowed with the food, rather than to the ferment secreted by the stomach and other organs. Saliva caused the first stage of fermentation, but the second was due to the bile and the pancreatic juice. He identified physiological fermentation with chemical effervescence. He discarded such agencies as the demon Archaeus of Paracelsus, and contended that although he could not explain the various processes, physiological operations were due to chemical principles, and that air inhaled in respiration acted upon and altered the blood. Illness was due to abnormal chemical reactions in the body, and could therefore be counteracted by other reactions. These theories, connecting as they did chemistry with medicine, had a great influence on the development of the former science.He taught the use of various chemical medicines, such as silver nitrate, zinc sulphate, calomel, corrosive sublimate, and other salts of mercury. Nevertheless, he retained the old alchemical superstitions regarding the transmutation of metals.

==== Otto Tachenius ====
One of the best-known followers of Sylvius was Otto Tachenius (circa 1620—1690). He was one of the first to give quantitative data in chemistry, and greatly improved qualitative analysis.He observed the difference of colour when corrosive sublimate is precipitated by a fixed or by a volatile alkali, and noted the use of gallic acid as a test for other metals than iron.

=== Ch. XXIV The Quantitative Period ===
(From 1775 A.D. till 1900 A.D.) 1. The Phlogistonists: Dr. William Cullen to the Honourable Henry Cavendish[A]fter the close of the eighteenth century the... science was intimately connected with manufactures, commerce, and all the varied departments of human work and enterprise. To-day, no technical art or craft is independent of it.The importance of the theory of phlogiston... [I]t was... the first successful attempt to give a rational explanation of a number of different phenomena, and to correlate a number of isolated facts and observations, and assign... a common cause. It gave an intelligible account of... combustion, and led to the discovery of hydrogen, oxygen, and many other elements and compounds.If... we define phlogiston as "the property of combustibility,"...their ideas were not so far removed from our own, and... their knowledge was very considerable...[S]o soon as the balance was applied to the investigation of chemical processes, the phlogiston hypothesis had to make way for another... more correct explanation.[T]he first seven leaders of the Quantitative Period were in the main phlogistonists. Cullen, Black, Cavendish, Priestley, Bergman, Scheele, and Kirwan were, during the greater part of their lives, and in some cases till their death, believers in the phlogiston hypothesis. But they also, by insisting on the necessity of accurate estimation of weight and measure, laid the foundation of quantitative determinations...

==== William Cullen ====
William Cullen (1710—1790), was celebrated rather as a physician than as a chemist, and owes his place in the history of the science mainly to his having been the teacher of Joseph Black.After being for a time Professor of Chemistry in Glasgow University, he went in the same capacity to Edinburgh, where he filled the chair for ten years... appointed Professor of the Institutes of Medicine.[D]etails of his life will be found in the biography by Dr. John Thomson, published in 1832.
Reference: An Account of the Life, Lectures, and Writings of William Cullen, M.D. by John Thompson, M.D. Vol. 1, Vol. 2.

==== Joseph Black ====
His Lectures on the Elements of Chemistry were published in 1803.
Reference: Lectures on the Elements of Chemistry (1806, 1807) Vol 1, 2, 3.An investigation into the means of dissolving urinary calculi led Black to study the action of quick lime in rendering alkalis caustic.At that time the causticity of these substances was held to be dependent on phlogiston.He showed in 1754 that causticisation meant not the gain, but the loss, of something. This he found to be a gas which he called "fixed air," and which was in 1781 named by Lavoisier "carbonic acid gas" (carbon dioxide).In this manner [he] re-discovered the gas silvestre of Van Helmont... [from] more than a hundred years before, but which had entirely escaped the memory of chemists. Black’s great thesis, "De Humore Acido a Cibis orto et Magnesia Alba" [On the Acid Humour Arising from Food, and Magnesia Alba] (1754), shook the phlogiston theory.[H]e demonstrated that magnesia alba when heated lost weight; that this loss was due to the escape of "fixed air"; and that its weight was regained when the calcined mass was made to re-absorb fixed air.Before Black’s time carbonates, such as magnesia alba (magnesium carbonate), were considered to be simple substances. When limestone was burned, chemists supposed that it took up "fire-stuff" and became caustic, and this "fire-stuff" passed on to potash and soda, when they were causticised by lime.His experiments on magnesia alba, quick lime, and other alkaline substances proved that "fixed air" is given off when limestone is burned, and that the same loss is incurred when it is dissolved in muriatic acid (hydrochloric acid).[M]ild alkalis, instead of taking up an acidum pingue, or fire-stuff, when they become caustic by the addition of quick lime, give up something to the lime, which then [returns to] its original weight, and capable of once more evolving fixed air. Therefore, it has received fixed air from the mild alkali. It now effervesces when treated with an acid, which quick lime will not do.Prior to Black, the action by which potassium carbonate in combination with slaked lime (calcium hydroxide) produces caustic potash (potassium hydroxide) and carbonate of lime, and which we express by the following equation:—K2CO3 + Ca(OH)2 = 2KOH + CaCO3was expressed thus:—Mild Alkali+(Mild lime+Phlogiston)=(Mild alkali+Phlogiston)+Mild lime.The bracketed terms, "mild lime plus phlogiston" and "mild alkali plus phlogiston," in this equation stand respectively for caustic lime and caustic alkali.Black found that by heating magnesia alba in a crucible, weight was lost, due in part to the loss of a little water, but chiefly to the loss of an "air." The product [had become] caustic, and on treatment with mild alkali gave the same weight as the original magnesia [alba], and acquired the property of effervescing with acids, which it had lost by the ignition.He... concluded that the effervescence was due to fixed air, and that caustic alkali in combination with fixed air became mild alkali. A similar treatment of limestone produced similar results.Black then neutralised some limestone with acid, and also a like amount of caustic lime obtained from the same quantity of limestone, and found that the amount of acid required to neutralise the substances was in both cases identical.Some confusion existed at that time between magnesia and limestone, but Black distinguished the one from the other by observing that when both were treated with oil of vitriol (sulphuric acid) fixed air was in each case given off, but the lime product formed a sediment in water, which the magnesia product did not.[H]e noted the great heat produced when water is added to quick lime, and attributed this to a strong affinity subsisting between the two.He inferred that an alkali, destitute of fixed air, became acrid and caustic, not because it had taken up phlogiston or an acidum pingue, but because of its powerful affinity.In the course of these experiments he was the first to distinguish, in 1756, ammonia from ammonium carbonate.Black's success in research work was largely due to his constant appeal to the balance... [I]t has been said that he laid the foundation of quantitative analysis.He... made many discoveries in physics. One of the most important... his doctrine of "latent heat,"... discovered in 1760... When ice melts it takes up a quantity of heat without undergoing any change in temperature. Black argued... this absorbed heat... combined with the particles of the ice, and become latent in its substance. He determined the latent heat of water... and... of steam... Watt, who was a personal friend of Black, made use of these... in his work on the steam-engine.Black further observed that different bodies in equal masses require different degrees of heat to raise them to the same temperature, and hence derived his theory of "specific heat."Lavoisier learned much from his correspondence [with Black]; but [Lavoisier] does not appear to have recognised fully his correspondent's important services.

==== Henry Cavendish ====
Black's work was... followed up... by the Honourable Henry Cavendish (1731—1810). He led a most retired life, devoted to scientific pursuits, chiefly in chemistry, but also in electricity, meteorology, and other departments of science. His quiet manner of life afforded no opportunity for spending his fortune...The scientific work of Cavendish is remarkable for its width of range, and its extreme accuracy.Eighteen papers by him were published in the Philosophical Transactions, of which ten were on chemical subjects.In 1766 Cavendish published his Experiments on F[a]ctitious Air... [which] showed that an inflammable air (hydrogen) was evolved when sulphuric or hydrochloric acid, diluted with water, was poured upon iron, zinc, or tin. He concluded that this [inflammable air] was the unaltered phlogiston of the metals. He was mistaken... but determined with fair accuracy the properties of the gas.
Reference: Three Papers, Containing Experiments on Factitious Air (1766) by the Hon. Henry Cavendish, F. R. S., Read May 29, Nov 6, and Nov 13, 1766, Philosophical Transactions of the Royal Society Received May 12, 1766.Following up Black's experiment, he obtained "fixed air" from marble acidulated with hydrochloric acid, examined its properties, and measured the quantity of it contained in different alkaline carbonates, in marble, and in the products of fermentation and decay.  He demonstrated, as Van Helmont had done a century before, that the gas from these different sources was the same.[In] the work of the chemists of this period... the four most important gases were...Other papers by Cavendish were: ....1767 on the salts found in water, particularly mineral waters, and on the solubility in water of bicarbonate of lime and magnesia; another on eudiometric experiments to determine the quantity of dephlogisticated air in the atmosphere; one to determine the freezing point of mercury... and one on freezing, in which he considered heat to be a rapid internal motion of the particles of a hot body.[T]he most valuable work of Cavendish was contained in the two papers "Experiments on Air" (1784-5)... to determine the phlogistication of air... [i.e.,] the change in air when metals are calcined in contact with it, and when sulphur, phosphorus, or similar substances, are burned in it.
Reference: XIII. Experiments on Air. Read Jan. 15, 1784. XXIII. Experiments on Air. Read June 2, 1785. Philosophical Transactions of the Royal Society.The following are his principal conclusions:—1. That fixed air is only produced when some animal or vegetable substance is present.2. That inflammable air, when mixed with common air and exploded, produces water, the relation of the volumes... 1 to 2.3. That nitrous gas gives nitric acid.4. That when electric sparks are passed through a mixture of dephlogisticated air and phlogisticated air, the gases combine and produce nitric acid.In his experiments with fixed air Cavendish... dried the gas by passing it over or through ignited pearl ashes... so, he was able to fix the specific gravity of the gas and of inflammable air. He also investigated their degree of absorption by liquids.Having... fired a mixture of inflammable air and an excess of dephlogisticated air, mixed with common air, he found nitric acid in the water produced. From this he assumed that an inert gas must be present. He called this gas "phlogisticated air."He... proceeded to inquire whether the whole of the phlogisticated air in a given quantity of common air could be reduced to nitric acid. He found that only 1/120th resisted change. ...[T]his small irreducible residue was probably argon and other analogous gases... not identified until more than a century later..Cavendish bestowed much attention upon heat, and might have anticipated Black's doctrines of latent and specific heal.In his own day, the part of his work which created the greatest sensation was his attempt to measure the density of the earth.

=== Ch. XXX The Rise of Electro-Chemistry ===
(From 1790 A.D. till 1820 A.D.)[T]he discovery of voltaic electricity by Galvani and Volta, and the controversy between these two pioneers of electric science in 1790, began to influence chemical research.Nicholson, the editor of Nicholson's s Philosophical Magazine, and Carlisle in 1800 repeated Volta’s experiments with the voltaic pile, performed electrolysis of water, distinguished the positive and negative poles, and established the connection between electricity and chemistry. ...They ...found that at the end of one wire hydrogen was evolved, while at the end of the other oxygen appeared, provided the metal of which the wire was made was not oxidisable. When the current was passed through tincture of litmus, they... noticed that the latter was coloured red in the neighbourhood of the positive pole, as if by an acid.Between 1803 and 1807 Berzelius and Hisinger in Sweden reported... [t]hat neutral salts are decomposed by the electric current; that, in general, chemical compounds are decomposed by the current, and their constituents collect at the poles; and that combustible substances, alkalis, and earths migrate to the negative pole; while oxygen, acids, and oxidised compounds migrate to the positive pole.

==== Humphry Davy ====
Gay-Lussac also worked on electro-decomposition, but the first to investigate completely electro-chemical decompositions, and to explain the laws which regulate them, was Sir Humphry Davy (1778—1829). ...An interesting narrative of his parentage and early years will be found in A History and Account of Penzance...the ancient town... chiefly devoted to mining, and... those who in early times came into contact with the Romans, and with traders from Europe and Africa, seeking tin from the famed Cassiterides.On the death of his father, Davy was apprenticed to Mr. Borlase, a surgeon and apothecary in Penzance, in whose house he began to show his interest in chemistry... While in the service of Mr. Borlase, Davy made the acquaintance of two visitors to Penzance, Gregory Watt, a son of the great engineer, and Davies Gilbert. The latter recommended him to Dr. Beddoes, Professor of Chemistry at Oxford. The doctor had established at Bristol a Medical Pneumatic Institution for investigating the medicinal properties of various gases, and in 1798 he made Davy superintendent...There [Davy] set to work upon original research, and amongst other things discovered that nitrous oxide was perfectly respirable, but produced absolute intoxication. In 1800 he published... "Researches, Chemical and Philosophical, chiefly concerning Nitrous Oxide or Dephlogisticated Nitrous Gas, and its Respiration." This treatise was the beginning of the use of nitrous oxide as an anæsthetic and intoxicant, and at once gave Davy a high reputation.Shortly before this Count Rumford had established the Royal Institution of London, and the first Professor of Chemistry, Dr. Garnet, having resigned, Davy was appointed in 1801 lecturer, and next year professor... As a lecturer he was extremely popular, his audience at the Royal Institution sometimes numbering a thousand.In 1802, at the request of the Board of Agriculture, he delivered a course of lectures, which he continued for ten years, and then published as Elements of Agricultural Chemistry (1813).Davy was elected a member of the Royal Society in 1803, and delivered under its auspices his celebrated Bakerian Lectures. In the first of these, in 1806, "On some Chemical Agencies of Electricity," described by Berzelius as one of the most remarkable memoirs in the history of chemical theory, he demonstrated that hydrogen, alkaline substances, metals, and some metallic oxides are attracted by negatively electrified, and repelled by positively electrified, metallic surfaces; while, on the contrary, oxygen and acid substances are attracted by positively electrified, and repelled by negatively electrified, metallic surfaces.His great discovery, the production of metallic potassium and sodium by electrolysis... was made in 1807. Next year in his third Bakerian Lecture he dealt with this subject, and disproved the idea of Gay-Lussac that potassium is not a simple substance, but a compound of potash and hydrogen. At the same time he described the preparation of boron, which he then thought a metal.The study of chlorine next occupied his attention, and formed the subject of his fifth Bakerian Lecture in 1810. Discussing the nature of what was called oxymuriatic acid, he demonstrated that it was not a compound, but a simple substance, for which he proposed the name "chlorine," by which it has since been known.Trinity College, Dublin, in 1811 conferred upon him the degree of Doctor of Laws, the only honorary degree he received. He was knighted by the Prince Regent in 1812, and created a baronet in 1818.In 1812 his Elements of Chemical Philosophy was published, and next year he travelled on the Continent. During this journey, while in Paris, he examined iodine, and declared it to be an element...The numerous accidents in mines caused by explosions of fire-damp led him to study the principles of the ignition of explosive gases. After an investigation on the spot, he invented the safety-lamp, which bears his name... declined to patent his idea [and] left it free for the benefit of all miners.Davy commenced his researches with the newly discovered Voltaic electricity, especially its chemical effects. ...It had previously been observed that when two platinum wires from a battery are plunged into water, an acid appears round the positive, and an alkali round the negative wire, but both... had been variously explained. Davy proved that in all cases these are derived from the decomposition of some salt dissolved in the water. On this observation he founded the Electro-chemical Theory of Affinity. He asserted that all substances which have chemical affinity for each other are in different states of electricity, one positive, the other negative; and that the degree of affinity is proportional to the intensity of these opposite states. When a compound is placed in contact with the poles of a galvanic battery, the positive pole attracts the electro-negative and repels the electro-positive, while the negative pole acts in the opposite way.He noticed that when copper and sulphur are mixed, they exhibit an electric potential, which increases with increasing temperature until finally they combine, and all traces of electricity disappear. Hence, he inferred that the same forces which, acting on masses at a distance, produce electric phenomena, when acting on atoms at small distances, produce chemical combination, the positive electricity of the one atom attracting and holding the negative of the other. In electrolysis the positive charge is on one and the negative on the other, but these two charges have to be discharged through the electrode before the elements are set free. This is the reverse of what takes place in combination. Davy in this view differed from the electro-chemical theory of Berzelius.Davy held that if the battery is strong enough any compound may be decomposed, and that chemical affinity is merely a form of electric attraction. He vigorously put his theory into practice, and by means of a powerful battery of 500 cells decomposed in 1807 [caustic] potash and [caustic] soda, and in 1808 [quick]lime, magnesia, strontia, baryta, and lithia, yielding the metals potassium, sodium, calcium, magnesium, strontium, barium, and lithium.The method he adopted was to pass a current from the Voltaic pile through a solution of caustic potash or soda, which was then believed to be an element, and thus obtain metallic potassium or sodium, as the case might be, at the negative pole. He inferred that these caustic alkalis are hydrates, and guessed that the alkaline earths have a similar constitution.Gay-Lussac and Thenard... prepared potassium by heating potassium hydroxide (caustic potash) with red-hot iron filings. On passing gaseous ammonia (NH3) over the metal thus obtained, they evolved hydrogen, and consequently refused to believe the simple nature of potassium, declaring it to be a compound of potash and hydrogen. Davy met this by maintaining that potassamide (the substance they obtained) is a potassium-substitution compound of ammonia.Another far-reaching result of Davy’s research was the proof of the elemental nature of chlorine. Berthollet’s conclusion that chlorine is oxymuriatic acid was universally accepted until Gay-Lussac and Thenard in 1809 endeavoured to decompose the gas and failed. They concluded that it contained water, because it yielded water when passed over litharge. Their researches read to the Institute in 1809 led Davy to investigate muriatic acid (hydrochloric acid) gas, which in 1808 he had shown to be decomposed by potassium, with evolution of hydrogen.In 1810 he proved that chlorine is an element, and that muriatic acid gas is a compound of chlorine and hydrogen. He thus overturned the oxygen-acid theory [of Antoine Lavoisier], and demonstrated that muriates are compounds of metals with chlorine. He pointed to the fact that some acids, such as sulphuretted hydrogen, contain no oxygen, and argued that muriatic acid gas was one of these, chlorine in it taking the place of oxygen.He used the following arguments to show that there is no oxygen in muriatic acid gas:—The conclusions of Davy were at first doubted, but when iodine and bromine were also discovered, Gay-Lussac and his followers adopted Davy’s views. The latter worked out fluorine, and proved that hydrofluoric acid (HF) contains no oxygen.Berzelius also opposed Davy until the discovery of iodine, but embraced the latter’s opinion in 1820.

==== Jons Jakob Berzelius ====
One of the greatest contemporaries of Davy and Dalton was the Swedish chemist Jons Jakob Berzelius (1779—1848). He... studied medicine at the University of Upsala, especially chemistry under Afzelius. His first chemical research was an analysis of mineral waters in 1799.Graduating as Doctor of Medicine in 1802, his thesis was "On the Action of Galvanism on Organic Bodies," in which he made use of the discovery in 1800 by Volta of the battery known by his name.Next year, in an essay "On the Division of Salts through Galvanism," he propounded a theory of electro-chemistry.Berzelius spent ten years in ascertaining with unprecedented care and accuracy the atomic or molecular weights of over two thousand simple and compound bodies. The results were published in 1818, and revised in 1826. In making these calculations he regarded oxygen as the pivot round which chemistry revolves, and therefore took it as the basis of reference for atomic weights. The greater part of his figures bear comparison with the most accurate determinations of more modern date.In 1815 he applied the Atomic Theory to the mineral kingdom, and made a new arrangement of minerals, founded on their being definite chemical compounds.As the outcome of his study of voltaic electricity, he proposed a theory based upon the supposition that the atoms of elements are electrically polarised, the positive charge predominating in some, and the negative in others.He also put forward a dualistic hypothesis that chemical compounds are composed of two electrically different components. In extending this hypothesis to organic chemistry, he regarded organic compounds as containing a group or groups of atoms forming compound radicles, in place of simple substances or elements. Although his views never commanded full assent from other chemists, he is... one of the founders of the Radicle Theory.One of his most useful services to chemistry was the invention of a system of symbols and notation, which with modification is still used in stating chemical formulæ.He indicated each simple substance or element by the initial letter (or, where more than one had the same initial, by two letters) of its Latin or Greek name. In the case of compound bodies he added a small subscript figure to show the number of atoms of each element present in the compound when these atoms exceeded unity. Thus:—Oxygen was represented by the letter O.Hydrogen was represented by the letter H.Mercury was represented by the letters Hg (Hydrargyrum).Lead was represented by the letters Pb (Plumbum).Water, a compound of two atoms of hydrogen and one of oxygen, was represented by H2O.Litharge, a compound of one atom each of lead and oxygen, was represented by PbO.He analysed many rare minerals; in 1818 discovered selenium, selenic acid, and its compounds; in 1822 studied the mineral waters of Carlsbad; in 1823 made experiments on uranium, fluoric acid, and pure silicon; in 1824 zirconium and tantalum; in 1826 thio acids and those salts in which sulphur was held to replace oxygen; in 1828 examined palladium, rhodium, osmium, iridium; in 1833 tellurium and thio derivatives; and in 1834 meteoric stones.Davy and Berzelius were chemists of the first rank in all branches of the science; but... [in] electro-chemistry... they were the leading pioneers.

== See also ==
Historical View of the Progress of Chemistry by Sir Humphry Davy
History of chemistry
History of Chemistry by Sir Thomas Edward Thorpe
Phlogiston theory
Scientific Revolution

== External links ==

A History of Chemistry from the Earliest Times till the Present Day (1913)
A History of Chemistry from the Earliest Times (1920)