Thomas Thomson

OF THE PROGRESS OF PHILOSOPHICAL CHEMISTRY IN SWEDEN.

Though Sweden, partly in consequence of her scanty population, and the consequent limited sale of books in that country, and partly from the propensity of her writers to imitate the French, which has prevented that originality in her poets and historians that is requisite for acquiring much eminence—though Sweden, for these reasons, has never reached a very high rank in literature; yet the case has been very different in science. She has produced men of the very first eminence, and has contributed more than her full share in almost every department of science, and in none has she shone with greater lustre than in the department of Chemistry. Even in the latter part of the seventeenth century, before chemistry had, properly speaking, assumed the rank of a science, we find Hierne in Sweden, whose name deserves to be mentioned with respect. Moreover, in the earlier part of the eighteenth century, Brandt, Scheffer, and Wallerius, had distinguished themselves by their writings. Cronstedt, about the middle of the eighteenth century, may be said to have laid the foundation of systematic mineralogy upon chemical principles, by the publication of his System of Mineralogy. But Bergman is entitled to the merit of being the first person who prosecuted chemistry in Sweden on truly philosophical principles, and raised it to that high estimation to which its importance justly entitles it.

Torbern Bergman was born at Catherinberg, in West Gothland, on the 20th of March, 1735. His father, Barthold Bergman, was receiver of the revenues of that district, and his mother, Sara HÄgg, the daughter of a Gotheborg merchant. A receiver of the revenues was at that time, in Sweden, a post both disagreeable and hazardous. The creatures of a party which had had the ascendancy in one diet, they were exposed to the persecution of the diet next following, in which an opposite party usually had the predominance. This circumstance induced Bergman to advise his son to turn his attention to the professions of law or divinity, which were at that time the most lucrative in Sweden. After having spent the usual time at school, and acquired those branches of learning commonly taught in Sweden, in the public schools and academies to which Bergman was sent, he went to the University of Upsala, in the autumn of 1752, where he was placed under the guidance of a relation, whose province it was to superintend his studies, and direct them to those pursuits that were likely to lead young Bergman to wealth and distinction. Our young student showed at once a decided predilection for mathematics, and those branches of physics which were connected with mathematics, or depended upon them. But these were precisely the branches of study which his relation was anxious to prevent his indulging in. Bergman attempted at once to indulge his own inclination, and to gratify the wishes of his relation. This obliged him to study with a degree of ardour and perseverance which has few examples. His mathematical and physical studies claimed the first share of his attention; and, after having made such progress in them as would alone have been sufficient to occupy the whole time of an ordinary student—to satisfy his relation, Jonas Victorin, who was at that time a magister docens in Upsala, he thought it requisite to study some law books besides, that he might be able to show that he had not neglected his advice, nor abandoned the views which he had held out.

He was in the habit of rising to his studies every morning at four o'clock, and he never went to bed till eleven at night. The first year of his residence at Upsala, he had made himself master of Wolf's Logic, of Wallerius's System of Chemistry, and of twelve books of Euclid's Elements: for he had already studied the first book of that work in the Gymnasium before he went to college. He likewise perused Keil's Lectures on Astronomy, which at that time were considered as the best introduction to physics and astronomy. His relative disapproved of his mathematical and physical studies altogether; but, not being able to put a stop to them, he interdicted the books, and left his young charge merely the choice between law and divinity. Bergman got a small box made, with a drawer, into which he put his mathematical and physical books, and over this box he piled the law books which his relative had urged him to study. At the time of the daily visits of his relative, the mathematical and physical books were carefully locked up in the drawer, and the law books spread upon the table; but no sooner was his presence removed, than the drawer was opened, and the mathematical studies resumed.

This incessant study; this necessity under which he found himself to consult his own inclinations and those of his relative; this double portion of labour, without time for relaxation, exercise, or amusement, proved at last injurious to young Bergman's health. He fell ill, and was obliged to leave the university and return home to his father's house in a state of bad health. There constant and moderate exercise was prescribed him, as the only means of restoring his health. That his time here might not be altogether lost to him, he formed the plan of making his walks subservient to the study of botany and entomology.

At this time LinnÆus, after having surmounted obstacles which would have crushed a man of ordinary energy, was in the height of his glory; and was professor of botany and natural history in the University of Upsala. His lectures were attended by crowds of students from every country in Europe: he was enthusiastically admired and adored by his students. This influence on the minds of his pupils was almost unbounded; and at Upsala, every student was a natural historian. Bergman had studied botany before he went to college, and he had acquired a taste for entomology from the lectures of LinnÆus himself. Both of these pursuits he continued to follow after his return home to West Gothland; and he made a collection of plants and of insects. Grasses and mosses were the plants to which he turned the most of his attention, and of which he collected the greatest number. But he felt a predilection for the study of insects, which was a field much less explored than the study of plants.

Among the insects which he collected were several not to be found in the Fauna Suecica. Of these he sent specimens to LinnÆus at Upsala, who was delighted with the present. All of them were till then unknown as Swedish insects, and several of them were quite new. The following were the insects at this time collected by Bergman, and sent to Upsala, as they were named by LinnÆus:

When Bergman's health was re-established, he returned to Upsala with full liberty to prosecute his studies according to his own wishes, and to devote the whole of his time to mathematics, physics, and natural history. His relations, finding it in vain to combat his predilections for these studies, thought it better to allow him to indulge them.

He had made himself known to LinnÆus by the collection of insects which he had sent him from Catherinberg; and, drawn along by the glory with which LinnÆus was surrounded, and the zeal with which his fellow-students prosecuted such studies, he devoted a great deal of his attention to natural history. The first paper which he wrote upon the subject contained a discovery. There was a substance observed in some ponds not far from Upsala, to which the name of coccus aquaticus was given, but its nature was unknown. LinnÆus had conjectured that it might be the ovarium of some insect; but he left the point to be determined by future observations. Bergman ascertained that it was the ovum of a species of leech, and that it contained from ten to twelve young animals. When he stated what he had ascertained to LinnÆus, that great naturalist refused to believe it; but Bergman satisfied him of the truth of his discovery by actual observation. LinnÆus, thus satisfied, wrote under the paper of Bergman, Vidi et obstupui, and sent it to the academy of Stockholm with this flattering panegyric. It was printed in the Memoirs of that learned body for 1756 (p. 199), and was the first paper of Bergman's that was committed to the press.

He continued to prosecute the study of natural history as an amusement; though mathematics and natural philosophy occupied by far the greatest part of his time. Various useful papers of his, connected with entomology, appeared from time to time in the Memoirs of the Stockholm Academy; in particular, a paper on the history of insects which attack fruit-trees, and on the methods of guarding against their ravages: on the method of classing these insects from the forms of their larvÆ, a time when it would be most useful for the agriculturist to know, in order to destroy those that are hurtful: a great number of observations on this class of animals, so various in their shape and their organization, and so important for man to know—some of which he has been able to overcome, while others, defended by their small size, and powerful by their vast numbers, still continue their ravages; and which offer so interesting a sight to the philosopher by their labours, their manners, and their foresight.—Bergman was fond of these pursuits, and looked back upon them in afterlife with pleasure. Long after, he used to mention with much satisfaction, that by the use of the method pointed out by him, no fewer than seven millions of destructive insects were destroyed in a single garden, and during the course of a single summer.

About the year 1757 he was appointed tutor to the only son of Count Adolf Frederick Stackelberg, a situation which he filled greatly to the satisfaction both of the father and son, as long as the young count stood in need of an instructor. He took his master's degree in 1758, choosing for the subject of his thesis on astronomical interpolation. Soon after, he was appointed magister docens in natural philosophy, a situation peculiar to the University of Upsala, and constituting a kind of assistant to the professor. For his promotion to this situation he was obliged to M. Ferner, who saw how well qualified he was for it, and how beneficial his labours would be to the University of Upsala. In 1761 he was appointed adjunct in mathematics and physics, which, I presume, means that he was raised to the rank of an associate with the professor of these branches of science. In this situation it was his business to teach these sciences to the students of Upsala, a task for which he was exceedingly well fitted. During this period he published various tracts on different branches of physical science, particularly on the rainbow, the crepuscula, the aurora-borealis, the electrical phenomena of Iceland spar, and of the tourmalin. We find his name among the astronomers who observed the first transit of Venus over the sun, in 1761, whose results deserve the greatest confidence.1 His observations on the electricity of the tourmalin are important. It was he that first established the true laws that regulate these curious phenomena.

During the whole of this period he had been silently studying chemistry and mineralogy, though nobody suspected that he was engaged in any such pursuits. But in 1767 John Gottschalk Wallerius, who had long filled the chair of chemistry in the University of Upsala, with high reputation, resigned his chair. Bergman immediately offered himself as a candidate for the vacant professorship: and, to show that he was qualified for the office, published two dissertations on the Manufacture of Alum, which probably he had previously drawn up, and had lying by him. Wallerius intended to resign his chair in favour of a pupil or relation of his own, whom he had destined to succeed him. He immediately formed a party to oppose the pretensions of Bergman; and his party was so powerful and so malignant, that few doubted of their success: for it was joined by all those who, despairing of equalling the industry and reputation of Bergman, set themselves to oppose and obstruct his success. Such men unhappily exist in all colleges, and the more eminent a professor is, the more is he exposed to their malignant activity. Many of those who cannot themselves rise to any eminence, derive pleasure from the attempt to pull down the eminent to their own level. In these attempts, however, they seldom succeed, unless from some want of prudence and steadiness in the individual whom they assail. Bergman's Dissertations on Alum were severely handled by Wallerius and his party: and such was the influence of the ex-professor, that every body thought Bergman would be crushed by him.

Fortunately, Gustavus III. of Sweden, at that time crown prince, was chancellor of the university. He took up the cause of Bergman, influenced, it is said, by the recommendation of Von Swab, who pledged himself for his qualifications, and was so keen on the subject that he pleaded his cause in person before the senate. Wallerius and his party were of course baffled, and Bergman got the chair.

For this situation his previous studies had fitted him in a peculiar manner. His mathematical, physical, and natural-historical knowledge, so far from being useless, contributed to free him from prejudices, and to emancipate him from that spirit of routine under which chemistry had hitherto suffered. They gave to his ideas a greater degree of precision, and made his views more correct. He saw that mathematics and chemistry divided between them the whole extent of natural science, and that its bounds required to be enlarged, to enable it to embrace all the different branches of science with which it was naturally connected, or which depended upon it. He saw the necessity of banishing from chemistry all vague hypotheses and explanations, and of establishing the science on the firm basis of experiment. He was equally convinced of the necessity of reforming the nomenclature of chemistry, and of bringing it to the same degree of precision that characterized the language of the other branches of natural philosophy.

His first care, after getting the chair, was to make as complete a collection as he could of mineral substances, and to arrange them in order according to the nature of their constituents, as far as they had been determined by experiment. To another cabinet he assigned the Swedish minerals, ranged in a geographical manner according to the different provinces which furnished them.

When I was at Upsala, in 1812, the first of these collections still remained, greatly augmented by his nephew and successor, Afzelius. But no remains existed of the geographical collection. However, there was a very considerable collection of this kind in the apartments of the Swedish school of mines at Stockholm, under the care of Mr. Hjelm, which I had an opportunity of inspecting. It is not improbable that Bergman's collection might have formed the nucleus of this. A geographical collection of minerals, to be of much utility, should exhibit all the different formations which exist in the kingdom: and in a country so uniform in its nature as Sweden, the minerals of one county are very nearly similar to those of the other counties; with the exception of certain peculiarities derived from the mines, or from some formations which may belong exclusively to certain parts of the country, as, for example, the coal formations in the south corner of Sweden, near Helsinburg, and the porphyry rocks, in Elfsdale.

Bergman attempted also to make a collection of models of the apparatus employed in the different chemical manufactories, to be enabled to explain these manufactures with greater clearness to his students. I was informed by M. Ekeberg, who, in 1812, was magister docens in chemistry at Upsala, that these models were never numerous. Nor is it likely that they should be, as Sweden cannot boast of any great number of chemical manufactories, and as, in Bergman's time, the processes followed in most of the chemical manufactories of Europe were kept as secret as possible.

Thus it was Bergman's object to exhibit to his pupils specimens of all the different substances which the earth furnishes, with the order in which these productions are arranged on the globe—to show them the uses made of all these different productions—how practice had preceded theory and had succeeded in solving many chemical problems of the most complicated nature.

His lectures are said to have been particularly valuable. He drew around him a considerable number of pupils, who afterwards figured as chemical discoverers themselves. Of all these Assessor Gahn, of Fahlun, was undoubtedly the most remarkable; but Hjelm, Gadolin, the Elhuyarts, and various other individuals, likewise distinguished themselves as chemists.

After his appointment to the chemical chair at Upsala, the remainder of his life passed with very little variety; his whole time was occupied with his favourite studies, and not a year passed that he did not publish some dissertation or other upon some more or less important branch of chemistry. His reputation gradually extended itself over Europe, and he was enrolled among the number of the members of most scientific academies. Among other honourable testimonies of the esteem in which he was held, he was elected rector of the University of Upsala. This university is not merely a literary body, but owns extensive estates, over which it possesses great authority, and, having considerable control over its students, and enjoying considerable immunities and privileges (conferred in former times as an encouragement to learning, though, in reality, they serve only to cramp its energies, and throw barriers in the way of its progress), constitutes, therefore, a kind of republic in the midst of Sweden: the professors being its chiefs. But while, in literary establishments, all the institutions ought to have for an object to maintain peace, and free their members from every occupation unconnected with letters, the constitution of that university obliges its professors to attend to things very inconsistent with their usual functions; while it gives men of influence and ambition a desire to possess the power and patronage, though they may not be qualified to perform the duties, of a professor. Such temptations are very injurious to the true cause of science; and it were to be wished, that no literary body, in any part of the world, were possessed of such powers and privileges. When Bergman was rector, the university was divided into two great parties, the one consisting of the theological and law faculties, and the other of the scientific professors. Bergman's object was to preserve peace and agreement between these two parties, and to convince them that it was the interest of all to unite for the good of the university and the promotion of letters. The period of his magistracy is remarkable in the annals of the university for the small number of deliberations, and the little business recorded in the registers; and for the good sense and good behaviour of the students. The students in Upsala are numerous, and most of them are young men. They had been accustomed frequently to brave or elude the severity of the regulations; but during Bergman's rectorship they were restrained effectually by their respect for his genius, and their admiration of his character and conduct.

When the reputation of Bergman was at its height, in the year 1776, Frederick the Great of Prussia formed the wish to attach him to the Academy of Sciences of Berlin, and made him offers of such a nature that our professor hesitated for a short time as to whether he ought not to accept them. His health had been injured by the assiduity with which he had devoted himself to the double duty of teaching and experimenting. He might look for an alleviation of his ailments, if not a complete recovery, in the milder climate of Prussia, and he would be able to devote himself entirely to his academical duties; but other considerations prevented him from acceding to this proposal, tempting as it was. The King of Sweden had been his benefactor, and it was intimated to him that his leaving the kingdom would afflict that monarch. This information induced him, without further hesitation, to refuse the proposals of the King of Prussia. He requested of the king, his master, not to make him lose the merit of his sacrifice by augmenting his income; but to this demand the King of Sweden very properly refused to accede.

In the year 1771, Professor Bergman married a widow lady, Margaretha Catharina Trast, daughter of a clergyman in the neighbourhood of Upsala. By her he had two sons; but both of them died when infants. This lady survived her husband. The King of Sweden settled on her an annuity of 200 rix dollars, on condition that she gave up the library and apparatus of her late husband to the Royal Society of Upsala.

Bergman's health had been always delicate; indeed he seems never to have completely recovered the effects of his first year's too intense study at Upsala. He struggled on, however, with his ailments; and, by way of relaxation, was accustomed sometimes, in summer, to repair to the waters of Medevi—a celebrated mineral spring in Sweden, situated near the banks of the great inland lake, Wetter. One of these visits seems to have restored him to health for the time. But his malady returned in 1784 with redoubled violence. He was afflicted with hemorrhoids, and his daily loss of blood amounted to about six ounces. This constant drain soon exhausted him, and on the 8th of July, 1784, he died at the baths of Medevi, to which he had repaired in hopes of again benefiting by these waters.

The different tracts which he published, as they have been enumerated by Hjelm, who gave an interesting account of Bergman to the Stockholm Academy in the year 1785, amount to 106. They have been all collected into six octavo volumes entitled "Opuscula Torberni Bergman Physica et Chemica"—with the exception of his notes on Scheffer, his Sciagraphia, and his chapter on Physical Geography, which was translated into French, and published in the Journal des Mines (vol. iii. No. 15, p. 55). His Sciagraphia, which is an attempt to arrange minerals according to their composition, was translated into English by Dr. Withering. His notes on Scheffer were interspersed in an edition of the "Chemiske FÖrelÄsningar" of that chemist, published in 1774, which he seems to have employed as a text-book in his lectures: or, at all events, the work was published for the use of the students of chemistry at Upsala. There was a new edition of it published, after Bergman's death, in the year 1796, to which are appended Bergman's Tables of Affinities.

The most important of Bergman's chemical papers were collected by himself, and constitute the three first volumes of his Opuscula. The three last volumes of that work were published after his death. The fourth volume was published at Leipsic, in 1787, by Hebenstreit, and contains the rest of his chemical papers. The fifth volume was given to the world in 1788, by the same editor. It contains three chemical papers, and the rest of it is made up with papers on natural history, electricity, and other branches of physics, which Bergman had published in the earlier part of his life. The same indefatigable editor published the sixth volume in 1790. It contains three astronomical papers, two chemical, and a long paper on the means of preventing any injurious effects from lightning. This was an oration, delivered before the Royal Academy of Sciences of Stockholm, in 1764, probably at the time of his admission into the academy.

It would serve little purpose in the present state of chemical knowledge, to give a minute analysis of Bergman's papers. To judge of their value, it would be necessary to compare them, not with our present chemical knowledge, but with the state of the science when his papers were published. A very short general view of his labours will be sufficient to convey an idea of the benefits which the science derived from them.

1. His first paper, entitled "On the Aerial Acid," that is, carbonic acid, was published in 1774. In it he gives the properties of this substance in considerable detail, shows that it possesses acid qualities, and that it is capable of combining with the bases, and forming salts. What is very extraordinary, in giving an account of carbonate of lime and carbonate of magnesia, he never mentions the name of Dr. Black; though it is very unlikely that a controversy, which had for years occupied the attention of chemists, should have been unknown to him. Mr. Cavendish's name never once appears in the whole paper; though that philosopher had preceded him by seven or eight years. He informs us, that he had made known his opinions respecting the nature of this substance, to various foreign correspondents, among others to Dr. Priestley, as early as the year 1770, and that Dr. Priestley had mentioned his views on the subject, in a paper inserted in the Philosophical Transactions for 1772. Bergman found the specific gravity of carbonic acid gas rather higher than 1·5, that of air being 1. His result is not far from the truth. He obtained his gas, by mixing calcareous spar with dilute sulphuric acid. He shows that this gas has a sour taste, that it reddens the infusion of litmus, and that it combines with bases. He gives figures of the apparatus which he used. This apparatus demands attention. Though far inferior to the contrivances of Priestley, it answered pretty well, enabling him to collect the gas, and examine its properties.

It is unnecessary to enter into any further details respecting this paper. Whoever will take the trouble to compare it with Cavendish's paper on the same subject, will find that he had been anticipated by that philosopher in a great many of his most important facts. Under these circumstances, I consider as singular his not taking any notice of Cavendish's previous labours.

2. His next paper, "On the Analyses of Mineral Waters," was first published in 1778, being the subject of a thesis, supported by J. P. Scharenberg. This dissertation, which is of great length, is entitled to much praise. He lays therein the foundation of the mode of analyzing waters, such as is followed at present. He points out the use of different reagents, for detecting the presence of the various constituents in mineral water, and then shows how the quantity of each is to be determined. It would be doing great injustice to Bergman, to compare his analyses with those of any modern experimenter. At that time, the science was not in possession of any accurate analyses of the neutral salts, which exist in mineral waters. Bergman undertook these necessary analyses, without which, the determination of the saline constituents of mineral waters was out of the question. His determinations were not indeed accurate, but they were so much better than those that preceded them, and Bergman's character as an experimenter stood so high, that they were long referred to as a standard by chemists. The first attempt to correct them was by Kirwan. But Bergman's superior reputation as a chemist enabled his results still to keep their ground, till his character for accuracy was finally destroyed by the very accurate experiments which the discovery of the atomic theory rendered it necessary to make. These, when once they became generally known, were of course preferred, and Bergman's analyses were laid aside.

It is a curious and humiliating fact, as it shows how much chemical reputation depends upon situation, or accidental circumstances, that Wenzel had, in 1766, in his book on affinity, published much more accurate analyses of all these salts, than Bergman's—analyses indeed which were almost perfectly correct, and which have scarcely been surpassed, by the most careful ones of the present day. Yet these admirable experiments scarcely drew the attention of chemists; while the very inferior ones of Bergman were held up as models of perfection.

3. Bergman, not satisfied with pointing out the mode of analyzing mineral waters, attempted to imitate them artificially by chemical processes, and published two essays on the subject; in the first he showed the processes by which cold mineral waters might be imitated, and in the other, the mode of imitating hot mineral waters. The attempt was valuable, and served to extend greatly the chemical knowledge of mineral waters, and of the salts which they contain; but it was made at too early a period of the analytical art, to approach perfection. A similar remark applies to his analysis of sea-water. The water examined was brought by Sparmann from a depth of eighty fathoms, near the latitude of the Canaries: Bergman found in it only common salt, muriate of magnesia, and sulphate of lime. His not having discovered the presence of sulphate of magnesia is a sufficient proof of the imperfection of his analytical methods; the other constituents exist in such small quantity in sea-water that they might easily have been overlooked, but the quantity of sulphate of magnesia in sea-water is considerable.

4. I shall pass over the paper on oxalic acid, which constituted the subject of a thesis, supported in 1776, by John Afzelius Arfvedson. It is now known that oxalic acid was discovered by Scheele, not by Bergman. It is impossible to say how many of the numerous facts stated in this thesis were ascertained by Scheele, and how many by Afzelius. For, as Afzelius was already a magister docens in chemistry, there can be little doubt that he would himself ascertain the facts which were to constitute the foundation of his thesis. It is indeed now known that Bergman himself intrusted all the details of his experiments to his pupils. He was the contriver, while his pupils executed his plans. That Scheele has nowhere laid claim to a discovery of so much importance as that of oxalic acid, and that he allowed Bergman peaceably to bear away the whole credit, constitutes one of the most remarkable facts in the history of chemistry. Moreover, while it reflects so much credit on Scheele for modesty and forbearance, it seems to bear a little hard upon the character of Bergman. When he published the essay in the first volume of his Opuscula, in 1779, why did he not in a note inform the world that Scheele was the true discoverer of this acid? Why did he allow the discovery to be universally assigned to him, without ever mentioning the true state of the case? All this appeared so contrary to the character of Bergman, that I was disposed to doubt the truth of the statement, that Scheele was the discoverer of oxalic acid. When I was at Fahlun, in the year 1812, I took an opportunity of putting the question to Assessor Gahn, who had been the intimate friend of Scheele, and the pupil, and afterwards the friend of Bergman. He assured me that Scheele really was the discoverer of oxalic acid, and ascribed the omission of Bergman to inadvertence. Assessor Gahn showed me a volume of Scheele's letters to him, which he had bound up: they contained the history of all his chemical labours. I have little doubt that an account of oxalic acid would be found in these letters. If the son of Assessor Gahn, in whose possession these letters must now be, would take the trouble to inspect the volume in question, and to publish any notices respecting this acid which they may contain, he would confer an important favour on every person interested in the history of chemistry.

5. The dissertation on the manufacture of alum has been mentioned before. Bergman shows himself well acquainted with the processes followed, at least in Sweden, for making alum. He had no notion of the true constitution of alum; nor was that to be expected, as the discovery was thereby years later in being made. He thought that the reason why alum leys did not crystallize well was, that they contained an excess of acid, and that the addition of potash gave them the property of crystallizing readily, merely by saturating that excess of acid. Alum is a double salt, composed of three integrant particles of sulphate of alumina, and one integrant particle of sulphate of potash, or sulphate of ammonia. In some cases, the alum ore contains all the requisite ingredients. This is the case with the ore at Tolfa, in the neighbourhood of Rome. It seems, also, to be the case with respect to some of the alum ores in Sweden; particularly at Hoensoeter on Kinnekulle, in West Gothland, which I visited in 1812. If any confidence can be put in the statements of the manager of those works, no alkaline salt whatever is added; at least, I understood him to say so when I put the question.

6. In his dissertation on tartar-emetic, he gives an interesting historical account of this salt and its uses. His notions respecting the antimonial preparations best fitted to form it, are not accurate: nor, indeed, could they be expected to be so, till the nature and properties of the different oxides of antimony were accurately known. Antimony forms three oxides: now it is the protoxide alone that is useful in medicine, and that enters into the composition of tartar-emetic; the other two oxides are inert, or nearly so. Bergman was aware that tartar-emetic is a double salt, and that its constituents are tartaric acid, potash, and oxide of antimony; but it was not possible, in 1773, when his dissertation was published, to have determined the true constituents of this salt by analysis.

7. Bergman's paper on magnesia was also a thesis defended in 1775, by Charles Norell, of West Gothland, who in all probability made the experiments described in the essay. In the introduction we have a history of the discovery of magnesia, and he mentions Dr. Black as the person who first accurately made out its peculiar chemical characters, and demonstrated that it differs from lime. This essay contains a pretty full and accurate account of the salts of magnesia, considering the state of chemistry at the time when it was published. There is no attempt to analyze any of the magnesian salts; but, in his treatise on the analysis of mineral waters, he had stated the quantity of magnesia contained in one hundred parts of several of them.

8. His paper on the shapes of crystals, published in 1773, contains the germ of the whole theory of crystallization afterwards developed by M. Hauy. He shows how, from a very simple primary form of a mineral, other shapes may proceed, which seem to have no connexion with, or resemblance to the primary form. His view of the subject, so far as it goes, is the very same afterwards adopted by Hauy: and, what is very curious, Hauy and Bergman formed their theory from the very same crystalline shape of calcareous spar—from which, by mechanical divisions, the same rhombic nucleus was extracted by both. Nothing prevented Bergman from anticipating Hauy but a sufficient quantity of crystals to apply his theory to.2

9. In his paper on silica he gives us a history of the progress of chemical knowledge respecting this substance. Its nature was first accurately pointed out by Pott; though Glauber, and before him Van Helmont, were acquainted with the liquor silicus, or the combination of silica and potash, which is soluble in water. Bergman gives a detailed account of its properties; but he does not suspect it to possess acid properties. This great discovery, which has thrown a new light upon mineral bodies, and shown them all to be chemical combinations, was reserved for Mr. Smithson.

10. Bergman's experiments on the precious stones constitute the first rudiments of the method of analyzing stony bodies. His processes are very imperfect, and his apparatus but ill adapted to the purpose. We need not be surprised, therefore, that the results of his analyses are extremely wide of the truth. Yet, if we study his processes, we shall find in them the rudiments of the very methods which we follow at present. The superiority of the modern analyses over those of Bergman must in a great measure be ascribed to the platinum vessels which we now employ, and to the superior purity of the substances which we use as reagents in our analyses. The methods, too, are simplified and perfected. But we must not forget that this paper of Bergman's, imperfect as it is, constitutes the commencement of the art, and that fully as much genius and invention may be requisite to contrive the first rude processes, how imperfect soever they may be, as are required to bring these processes when once invented to a state of comparative perfection. The great step in analyzing minerals is to render them soluble in acids. Bergman first thought of the method for accomplishing this which is still followed, namely, fusing them or heating them to redness with an alkali or alkaline carbonate.

11. The paper on fulminating gold goes a great way to explain the nature of that curious compound. He describes the properties of this substance, and the effects of alkaline and acid bodies on it. He shows that it cannot be formed without ammonia, and infers from his experiments that it is a compound of oxide of gold and ammonia. He explains the fulmination by the elastic fluid suddenly generated by the decomposition of the ammonia.

12. The papers on platinum, carbonate of iron, nickel, arsenic, and zinc, do not require many remarks. They add considerably to the knowledge which chemists at that time possessed of these bodies; though the modes of analysis are not such as would be approved of by a modern chemist; nor were the results obtained possessed of much precision.

13. The Essay on the Analysis of Metallic Ores by the wet way, or by solution, constitutes the first attempt to establish a regular method of analyzing metallic ores. The processes are all imperfect, as might be expected from the then existing state of analytical chemistry, and the imperfect knowledge possessed, of the different metallic ores. But this essay constituted a first beginning, for which the author is entitled to great praise. The subject was taken up by Klaproth, and speedily brought to a great degree of improvement by the labours of modern chemists.

14. The experiments on the way in which minerals behave before the blowpipe, which Bergman published, were made at Bergman's request by Assessor Gahn, of Fahlun, who was then his pupil. They constitute the first results obtained by that very ingenious and amiable man. He afterwards continued the investigation, and added many improvements, simplifying the reagents and the manner of using them. But he was too indolent a man to commit the results of his investigations to writing. Berzelius, however, had the good sense to see the importance of the facts which Gahn had ascertained. He committed them to writing, and published them for the use of mineralogists. They constitute the book entitled "Berzelius on the Blowpipe," which has been translated into English.

15. The object of the Essay on Metallic Precipitates is to determine the quantity of phlogiston which each metal contains, deduced from the quantity of one metal necessary to precipitate a given weight of another. The experiments are obviously made with little accuracy: indeed they are not susceptible of very great precision. Lavoisier afterwards made use of the same method to determine the quantity of oxygen in the different metallic oxides; but his results were not more successful than those of Bergman.

16. Bergman's paper on iron is one of the most important in his whole works, and contributed very materially to advance the knowledge of the cause of the difference between iron and steel. He employed his pupils to collect specimens of iron from the different Swedish forges, and gave them directions how to select the proper pieces. All these specimens, to the number of eighty-nine, he subjected to a chemical examination, by dissolving them in dilute sulphuric acid. He measured the volume of hydrogen gas, which he obtained by dissolving a given weight of each, and noted the quantity and the nature of the undissolved residue. The general result of the whole investigation was that pure malleable iron yielded most hydrogen gas; steel less, and cast-iron least of all. Pure malleable iron left the smallest quantity of insoluble matter, steel a greater quantity, and cast-iron the greatest of all. From these experiments he drew conclusions with respect to the difference between iron, steel, and cast-iron. Nothing more was necessary than to apply the antiphlogistic theory to these experiments, (as was done soon after by the French chemists,) in order to draw important conclusions respecting the nature of these bodies. Iron is a simple body; steel is a compound of iron and carbon; and cast-iron of iron and a still greater proportion of carbon. The defective part of the experiments of Bergman in this important paper is his method of determining the quantity of manganese in iron. In some specimens he makes the manganese amount to considerably more than a third part of the weight of the whole. Now we know that a mixture of two parts iron and one part manganese is brittle and useless. We are sure, therefore, that no malleable iron whatever can contain any such proportion of manganese. The fact is, that Bergman's mode of separating manganese from iron was defective. What he considered as manganese was chiefly, and might be in many cases altogether, oxide of iron. Many years elapsed before a good process for separating iron from manganese was discovered.

17. Bergman's experiments to ascertain the cause of the brittleness of cold-short iron need not occupy much of our attention. He extracted from it a white powder, by dissolving the cold-short iron in dilute sulphuric acid. This white powder he succeeded in reducing to the state of a white brittle metal, by fusing it with a flux and charcoal. Klaproth soon after ascertained that this metal was a phosphuret of iron, and that the white powder was a phosphate of iron: and Scheele, with his usual sagacity, hit on a method of analyzing this phosphate, and thus demonstrating its nature. Thus Bergman's experiments led to the knowledge of the fact that cold-short iron owes its brittleness to a quantity of phosphorus which it contains. It ought to be mentioned that Meyer, of Stettin, ascertained the same fact, and made it known to chemists at about the same time with Bergman.

18. The dissertation on the products of volcanoes, first published in 1777, is one of the most striking examples of the sagacity of Bergman which we possess. He takes a view of all the substances certainly known to have been thrown out of volcanoes, attempts to subject them to a chemical analysis, and compares them with the basalt, and greenstone or trap-rocks, the origin of which constituted at that time a keen matter of dispute among geologists. He shows the identity between lavas and basalt and greenstone, and therefore infers the identity of formation. This is obviously the true mode of proceeding, and, had it been adopted at an earlier period, many of those disputes respecting the nature of trap-rocks, which occupied geologists for so long a period, would never have been agitated; or, at least, would have been speedily decided. The whole dissertation is filled with valuable matter, still well entitled to the attention of geologists. His observations on zeolites, which he considered as unconnected with volcanic products, were very natural at the time when he wrote: though the subsequent experiments of Sir James Hall, and Mr. Gregory Watt, and, above all, an accurate attention to the scoriÆ from different smelting-houses, have thrown a new light on the subject, and have shown the way in which zeolitic crystals might easily have been formed in melted lava, provided circumstances were favourable. In fact, we find abundant cavities in real lava from Vesuvius, filled with zeolitic crystals.

19. The last of the labours of Bergman which I shall notice here is his Essay on Elective Attractions, which was originally published in 1775, but was much augmented and improved in the third volume of his Opuscula, published in 1783. An English translation of this last edition of the Essay was made by Dr. Beddoes, and was long familiar to the British chemical world. The object of this essay was to elucidate and explain the nature of chemical affinity, and to account for all the apparent anomalies that had been observed. He laid it down as a first principle, that all bodies capable of combining chemically with each other, have an attraction for each other, and that this attraction is a definite and fixed force which may be represented by a number. Now the bodies which have the property of uniting together are chiefly the acids and the alkalies, or bases. Every acid has an attraction for each of the alkalies or bases; but the force of this attraction differs in each. Some bases have a strong attraction for acids, and others a weak; but the attractive force of each may be expressed by numbers.

Now, suppose that an acid a is united with a base m with a certain force, if we mix the compound a m with a certain quantity of the base n, which has a stronger attraction for a than m has, the consequence will be, that a will leave m and unite with n;—n having a stronger attraction for a than m has, will disengage it and take its place. In consequence of this property, which Bergman considered as the foundation of the whole of the science, the strength of affinity of one body for another is determined by these decompositions and combinations. If n has a stronger affinity for a than m has, then if we mix together a, m, and n in the requisite proportions, a and n will unite together, leaving m uncombined: or if we mix n with the compound a m, m will be disengaged. Tables, therefore, may be drawn up, exhibiting the strength of these affinities. At the top of a column is put the name of an acid or a base, and below it are put the names of all the bases or acids in the order of their affinity. The following little table will exhibit a specimen of these columns:

• Sulphuric Acid.
• Barytes
• Strontian
• Potash
• Soda
• Lime
• Magnesia.

Here sulphuric acid is the substance placed at the head of the column, and under it are the names of the bases capable of uniting with it in the order of their affinity. Barytes, which is highest up, has the strongest affinity, and magnesia, which is lowest down, has the weakest affinity. If sulphuric acid and magnesia were combined together, all the bases whose names occur in the table above magnesia would be able to separate the sulphuric acid from it. Potash would be disengaged from sulphuric acid by barytes and strontian, but not by soda, lime, and magnesia.

Such tables then exhibited to the eye the strength of affinity of all the different bodies that are capable of uniting with one and the same substance, and the order in which decompositions are effected. Bergman drew up tables of affinity according to these views in fifty-nine columns. Each column contained the name of a particular substance, and under it was arranged all the bodies capable of uniting with it, each in the order of its affinity. Now bodies may be made to unite, either by mixing them together, and then exposing them to heat, or by dissolving them in water and mixing the respective solutions together. The first of these ways is usually called the dry way, the second the moist way. The order of decompositions often varies with the mode employed. On this account, Bergman divided each of his fifty-nine columns into two. In the first, he exhibited the order of decompositions in the moist way, in the second in the dry. He explained also the cases of double decomposition, by means of these unvarying forces acting together or opposing each other—and gave sixty-four cases of such double decompositions.

These views of Bergman's were immediately acceded to by the chemical world, and continued to regulate their processes till Berthollet published his Chemical Statics in 1802. He there called in question the whole doctrine of Bergman, and endeavoured to establish one of the very opposite kind. I shall have occasion to return to the subject when I come to give an account of the services which Berthollet conferred upon chemistry.

I have already observed, that we are under obligations to Bergman, not merely for the improvements which he himself introduced into chemistry, but for the pupils whom he educated as chemists, and the discoveries which were made by those persons, whose exertions he stimulated and encouraged. Among those individuals, whose chemical discoveries were chiefly made known to the world by his means, was Scheele, certainly one of the most extraordinary men, and most sagacious and industrious chemists that ever existed.

Charles William Scheele was born on the 19th of December, 1742, at Stralsund, the capital of Swedish Pomerania, where his father was a tradesman. He received the first part of his education at a private academy in Stralsund, and was afterwards removed to a public school. At a very early period he expressed a strong desire to study pharmacy, and obtained his father's consent to make choice of this profession. He was accordingly bound an apprentice for six years to Mr. Bouch, an apothecary in Gotheborg, and after his time was out, he remained with him still, two years longer.

It was here that he laid the groundwork of all his future celebrity, as we are informed by Mr. Grunberg, who was his fellow-apprentice, and afterwards settled as an apothecary in Stralsund. He was at that time very reserved and serious, but uncommonly diligent. He attended minutely to all the processes, reflected upon them while alone, and studied the writings of Neumann, Lemery, Kunkel, and Stahl, with indefatigable industry. He likewise exercised himself a good deal in drawing and painting, and acquired some proficiency in these accomplishments without a master. Kunkel's Laboratorium was his favourite book, and he was in the habit of repeating experiments out of it secretly during the night-time. On one occasion, as he was employed in making pyrophorus, his fellow-apprentice was malicious enough to put a quantity of fulminating powder into the mixture. The consequence was a violent explosion, which, as it took place in the night, threw the whole family into confusion, and brought a very severe rebuke upon our young chemist. But this did not put a stop to his industry, which he pursued so constantly and judiciously, that, by the time his apprenticeship was ended, there were very few chemists indeed who excelled him in knowledge and practical skill. His fellow-apprentice, Mr. Grunberg, wrote to him in 1774, requesting to know by what means he had become such a proficient in chemistry, and received the following answer: "I look upon you, my dear friend, as my first instructor, and as the author of all I know on the subject, in consequence of your advising me to read Neumann's Chemistry. The perusal of this book first gave me a taste for experimenting, myself; and I very well remember, that upon mixing some oil of cloves and smoking spirit of nitre together, they took fire. However, I kept this matter secret. I have also before my eyes the unfortunate experiment which I made with pyrophorus. Such accidents only served to increase my passion for making experiments."

In 1765 Scheele went to Malmo, to the house of an apothecary, called Mr. Kalstrom. After spending two years in that place, he went to Stockholm, to superintend the apothecary's shop of Mr. Scharenberg. In 1773 he exchanged this situation for another at Upsala, in the house of Mr. Loock. It was here that he accidentally formed an acquaintance with Assessor Gahn, of Fahlun, who was at that time a student at Upsala, and a zealous chemist. Mr. Gahn happening to be one day in the shop of Mr. Loock, that gentleman mentioned to him a circumstance which had lately occurred to him, and of which he was anxious to obtain an explanation. If a quantity of saltpetre be put into a crucible and raised to such a temperature as shall not merely melt it, but occasion an agitation in it like boiling, and if, after a certain time, the crucible be taken out of the fire and allowed to cool, the saltpetre still continues neutral; but its properties are altered: for, if distilled vinegar be poured upon it, red fumes are given out, while vinegar produces no effect upon the saltpetre before it has been thus heated. Mr. Loock wished from Gahn an explanation of the cause of this phenomenon: Gahn was unable to explain it; but promised to put the question to Professor Bergman. He did so accordingly, but Bergman was as unable to find an explanation as himself. On returning a few days after to Mr. Loock's shop, Gahn was informed that there was a young man in the shop who had given an explanation of the phenomenon. This young man was Scheele, who had informed Mr. Loock that there were two species of acids confounded under the name of spirit of nitre; what we at present call nitric and hyponitrous acids. Nitric acid has a stronger affinity for potash than vinegar has; but hyponitrous acid has a weaker. The heat of the fire changes the nitric acid of the saltpetre to hyponitrous: hence the phenomenon.

Gahn was delighted with the information, and immediately formed an acquaintance with Scheele, which soon ripened into friendship. When he informed Bergman of Scheele's explanation, the professor was equally delighted, and expressed an eager desire to be made acquainted with Scheele; but when Gahn mentioned the circumstance to Scheele, and offered to introduce him to Bergman, our young chemist rejected the proposal with strong feelings of dislike.

It seems, that while Scheele was in Stockholm, he had made experiments on cream of tartar, and had succeeded in separating from it tartaric acid, in a state of purity. He had also determined a number of the properties of tartaric acid, and examined several of the tartrates. He drew up an account of these results, and sent it to Bergman. Bergman, seeing a paper subscribed by the name of a person who was unknown to him, laid it aside without looking at it, and forgot it altogether. Scheele was very much provoked at this contemptuous and unmerited treatment. He drew up another account of his experiments and gave it to Retzius, who sent it to the Stockholm Academy of Sciences (with some additions of his own), in whose Memoirs it was published in the year 1770.3 It cost Assessor Gahn considerable trouble to satisfy Scheele that Bergman's conduct was merely the result of inadvertence, and that he had no intention whatever of treating him either with contempt or neglect. After much entreaty, he prevailed upon Scheele to allow him to introduce him to the professor of chemistry. The introduction took place accordingly, and ever after Bergman and Scheele continued steady friends—Bergman facilitating the researches of Scheele by every means in his power.

So high did the character of Scheele speedily rise in Upsala, that when the Duke of Sudermania visited the university soon after, in company with Prince Henry of Prussia, Scheele was appointed by the university to exhibit some chemical processes before him. He fulfilled his charge, and performed in different furnaces several curious and striking experiments. Prince Henry asked him various questions, and expressed satisfaction at the answers given. He was particularly pleased when informed that he was a native of Stralsund. These two princes afterwards stated to the professors that they would take it as a favour if Scheele could have free access to the laboratory of the university whenever he wished to make experiments.

In the year 1775, on the death of Mr. Popler, apothecary at KÖping (a small place on the north side of the lake MÆler), he was appointed by the Medical College provisor of the apothecary's shop. In Sweden all the apothecaries are under the control of the Medical College, and no one can open a shop without undergoing an examination and receiving licence from that learned body. In the course of the examinations which he was obliged to undergo, Scheele gave great proofs of his abilities, and obtained the appointment. In 1777 the widow sold him the shop and business, according to a written agreement made between them; but they still continued housekeeping at their joint expense. He had already distinguished himself by his discovery of fluoric acid, and by his admirable paper on manganese. It is said, too, that it was he who made the experiments on carbonic acid gas, which constitute the substance of Bergman's paper on the subject, and which confirmed and established Bergman's idea that it was an acid. At KÖping he continued his researches with unremitting perseverance, and made more discoveries than all the chemists of his time united together. It was here that he made the experiments on air and fire, which constitute the materials of his celebrated work on these subjects. The theory which he formed was indeed erroneous; but the numerous discoveries which the book contains must always excite the admiration of every chemist. His discovery of oxygen gas had been anticipated by Priestley; but his analysis of atmospheric air was new and satisfactory—was peculiarly his own. The processes by means of which he procured oxygen gas were also new, simple, and easy, and are still followed by chemists in general. During his residence at KÖping he published a great number of chemical papers, and every one of them contained a discovery. The whole of his time was devoted to chemical investigations. Every action of his life had a tendency to forward the advancement of his favourite science; all his thoughts were turned to the same object; all his letters were devoted to chemical observations and chemical discussions. Crell's Annals was at that time the chief periodical work on chemistry in Germany. He got the numbers regularly as they were published, and was one of Crell's most constant and most valuable correspondents. Every one of his letters published in that work either contains some new chemical fact, or exposes the errors and mistakes of some one or other of Crell's numerous correspondents.

Scheele's outward appearance was by no means prepossessing. He seldom joined in the usual conversations and amusements of society, having neither leisure nor inclination for them. What little time he had to spare from the hurry of his profession was always employed in making experiments. It was only when he received visits from his friends, with whom he could converse on his favourite science, that he indulged himself in a little relaxation. For such intimate friends he had a sincere affection. This regard was extended to all the zealous cultivators of chemistry in every part of the world, whether personally known to him or not. He kept up a correspondence with several; though this correspondence was much limited by his ignorance of all languages except German; for at least he could not write fluently in any other language. His chemical papers were always written in German, and translated into Swedish, before they were inserted in the Memoirs of the Stockholm Academy, where most of them appeared.

He was kind and affable to all. Before he adopted an opinion in science, he reflected maturely on it; but, after he had once embraced it, his opinions were not easily shaken. However, he did not hesitate to give up an opinion as soon as it had been proved to be erroneous. Thus, he entirely renounced the notion which he once entertained that silica is a compound of water and fluoric acid; because it was demonstrated, by Meyer and others, that this silica was derived from the glass vessels in which the fluoric acid was prepared; that these glass vessels were speedily corroded into holes; and that, if fluoric acid was prepared in metallic vessels, and not allowed to come in contact with glass or any substance containing silica, it might be mixed with water without any deposition of silica whatever.

It appears also by a letter of his, published in Crell's Annals, that he was satisfied of the accuracy of Mr. Cavendish's experiments, showing that water was a compound of oxygen and hydrogen gases, and of Lavoisier's repetition of them. He attempted to reconcile this fact with his own notion, that heat is a compound of oxygen and hydrogen. But his arguments on that subject, though ingenious, are not satisfactory; and there is little doubt that if he had lived somewhat longer, and had been able to repeat his own experiments, and compare them with those of Cavendish and Lavoisier, he would have given up his own theory and adopted that of Lavoisier, or, at any rate, the explanation of Cavendish, which, being more conformable to his own preconceived notions, might have been embraced by him in preference.

It is said by Dr. Crell that Scheele was invited over to England, with an offer of an easy and advantageous situation; but that his love of quiet and retirement, and his partiality for Sweden, where he had spent the greatest part of his life, threw difficulties in the way of these overtures, and that a change in the English ministry put a stop to them for the time. The invitation, Crell says, was renewed in 1786, with the offer of a salary of 300l. a-year; but Scheele's death put a final stop to it. I have very great doubts about the truth of this statement; and, many years ago, during the lifetime of Sir Joseph Banks, Mr. Cavendish, and Mr. Kirwan, I made inquiry about the circumstance; but none of the chemists in Great Britain, who were at that time numerous and highly respectable, had ever heard of any such negotiation. I am utterly at a loss to conceive what one individual in any of the ministries of George III. was either acquainted with the science of chemistry, or at all interested in its progress. They were all so intent upon accomplishing their own objects, or those of their sovereign, that they had neither time nor inclination to think of science, and certainly no money to devote to any of its votaries. What minister in Great Britain ever attempted to cherish the sciences, or to reward those who cultivate them with success? If we except Mr. Montague, who procured the place of master of the Mint for Sir Isaac Newton, I know of no one. While in every other nation in Europe science is directly promoted, and considerable sums are appropriated for its cultivation, and for the support of a certain number of individuals who have shown themselves capable of extending its boundaries, not a single farthing has been devoted to any such purpose in Great Britain. Science has been left entirely to itself; and whatever has been done by way of promoting it has been performed by the unaided exertions of private individuals. George III. himself was a patron of literature and an encourager of botany. He might have been disposed to reward the unrivalled eminence which Scheele had attained; but this he could only have done by bestowing on him a pension out of his privy purse. No situation which Scheele could fill was at his disposal. The universities and the church were both shut against a Lutheran; and no pharmaceutical places exist in this country to which Scheele could have been appointed. If any such project ever existed, it must have been an idea which struck some man of science that such a proposal to a man of Scheele's eminence would redound to the credit of the country. But that such a project should have been broached by a British ministry, or by any man of great political influence, is an opinion that no person would adopt who has paid any attention to the history of Great Britain since the Revolution to the present time.

Scheele fell at last a sacrifice to his ardent love for his science. He was unable to abstain from experimenting, and many of his experiments were unavoidably made in his shop, where he was exposed during winter, in the ungenial climate of Sweden, to cold draughts of air. He caught rheumatism in consequence, and the disease was aggravated by his ardour and perseverance in his pursuits. When he purchased the apothecary's shop in which his business was carried on, he had formed the resolution of marrying the widow of his predecessor, and he had only delayed it from the honourable principle of acquiring, in the first place, sufficient property to render such an alliance desirable on her part. At length, in the month of March, 1786, he declared his intention of marrying her; but his disease at this time increased very fast, and his hopes of recovery daily diminished. He was sensible of this; but nevertheless he performed his promise, and married her on the 19th of May, at a time when he lay on his deathbed. On the 21st, he left her by his will the disposal of the whole of his property; and, the same day on which he so tenderly provided for her, he died.

I shall now endeavour to give the reader an idea of the principal chemical discoveries for which we are indebted to Scheele: his papers, with the exception of his book on air and fire, which was published separately by Bergman, are all to be found either in the Memoirs of the Stockholm Academy of Science, or in Crell's Journal; they were collected, and a Latin translation of them, made by Godfrey Henry Schaefer, published at Leipsic, in 1788, by Henstreit, the editor of the three last volumes of Bergman's Opuscula. A French translation of them was made in consequence of the exertions of M. Morveau; and an English translation of them, in 1786, by means of Dr. Beddoes, when he was a student in Edinburgh. There are also several German translations, but I have never had an opportunity of seeing them.

1. Scheele's first paper was published by Retzius, in 1770; it gives a method of obtaining pure tartaric acid: the process was to decompose cream of tartar by means of chalk. One half of the tartaric acid unites to the lime, and falls down in the state of a white insoluble powder, being tartrate of lime. The cream of tartar, thus deprived of half its acid, is converted into the neutral salt formerly distinguished by the name of soluble tartar, from its great solubility in water: it dissolves, and may be obtained in crystals, by the usual method of crystallizing salts. The tartrate of lime is washed with water, and then mixed with a quantity of dilute sulphuric acid, just capable of saturating the lime contained in the tartrate of lime; the mixture is digested for some time; the sulphuric acid displaces the tartaric acid, and combines with the lime; and, as the sulphate of lime is but very little soluble in water, the greatest part of it precipitates, and the clear liquor is drawn off: it consists of tartaric acid, held in solution by water, but not quite free from sulphate of lime. By repeated concentrations, all the sulphate of lime falls down, and at last the tartaric acid itself is obtained in large crystals. This process is still followed by the manufacturers of this country; for tartaric acid is used to a very considerable extent by the calico-printers, in various processes; for example, it is applied, thickened with gum, to different parts of cloth dyed Turkey red; the cloth is then passed through water containing the requisite quantity of chloride of lime: the tartaric acid, uniting with the lime, sets the chlorine at liberty, which immediately destroys the red colour wherever the tartaric acid has been applied, but leaves all the other parts of the cloth unchanged.

2. The paper on fluoric acid appeared in the Memoirs of the Stockholm Academy, for 1771, when Scheele was in Scharenberg's apothecary's shop in Stockholm, where, doubtless, the experiments were made. Three years before, Margraaf had attempted an analysis of fluor spar, but had discovered nothing. Scheele demonstrated that it is a compound of lime and a peculiar acid, to which he gave the name of fluoric acid. This acid he obtained in solution in water; it was separated from the fluor spar by sulphuric, muriatic, nitric, and phosphoric acids. When the fluoric acid came in contact with water, a white crust was formed, which proved, on examination, to be silica. Scheele at first thought that this silica was a compound of fluoric acid and water; but it was afterwards proved by Weigleb and by Meyer, that this notion is inaccurate, and that the silica was corroded from the retort into which the fluor spar and sulphuric acid were put. Bergman, who had adopted Scheele's theory of the nature of silica, was so satisfied by these experiments, that he gave it up, as Scheele himself did soon after.

Scheele did not obtain fluoric acid in a state of purity, put only fluosilicic acid; nor were chemists acquainted with the properties of fluoric acid till Gay-Lussac and Thenard published their Recherches Physico-chimiques, in 1811.

3. Scheele's experiments on manganese were undertaken at the request of Bergman, and occupied him three years; they were published in the Memoirs of the Stockholm Academy, for 1774, and constitute the most memorable and important of all his essays, since they contain the discovery of two new bodies, which have since acted so conspicuous a part, both in promoting the progress of the science, and in improving the manufactures of Europe. These two substances are chlorine and barytes, the first account of both of which occur in this paper.

The ore of manganese employed in these experiments was the black oxide, or deutoxide, of manganese, as it is now called. Scheele's method of proceeding was to try the effect of all the different reagents on it. It dissolved in sulphurous and nitrous acids, and the solution was colourless. Dilute sulphuric acid did not act upon it, nor nitric acid; but concentrated sulphuric acid dissolved it by the assistance of heat. The solution of sulphate of manganese in water was colourless and crystallized in very oblique rhomboidal prisms, having a bitter taste. Muriatic acid effervesced with it, when assisted by heat, and the elastic fluid that passed off had a yellowish colour, and the smell of aqua regia. He collected quantities of this elastic fluid (chlorine) in bladders, and determined some of its most remarkable properties: it destroyed colours, and tinged the bladder yellow, as nitric acid does. This elastic fluid, in Scheele's opinion, was muriatic acid deprived of phlogiston. By phlogiston Scheele meant, in this place, hydrogen gas. He considered muriatic acid as a compound of chlorine and hydrogen. Now this is the very theory that was established by Davy in consequence of his own experiments and those of Gay-Lussac and Thenard. Scheele's mode of collecting chlorine gas in a bladder, did not enable him to determine its characters with so much precision as was afterwards done. But his accuracy was so great, that every thing which he stated respecting it was correct so far as it went.

Most of the specimens of manganese ore which Scheele examined, contained more or less barytes, as has since been determined, in combination with the oxide. He separated this barytes, and determined its peculiar properties. It dissolved in nitric and muriatic acids, and formed salts capable of crystallizing, and permanent in the air. Neither potash, soda, nor lime, nor any base whatever, was capable of precipitating it from these acids. But the alkaline carbonates threw it down in the state of a white powder, which dissolved with effervescence in acids. Sulphuric acid and all the sulphates threw it down in the state of a white powder, which was insoluble in water and in acids. This sulphate cannot be decomposed by any acid or base whatever. The only practicable mode of proceeding is to convert the sulphuric acid into sulphur, by heating the salt with charcoal powder, along with a sufficient quantity of potash, to bring the whole into fusion. The fused mass, edulcorated, is soluble in nitric or muriatic acid, and thus may be freed from charcoal, and the barytes obtained in a state of purity. Scheele detected barytes, also, in the potash made from trees or other smaller vegetables; but at that time he was unacquainted with sulphate of barytes, which is so common in various parts of the earth, especially in lead-mines.

To point out all the new facts contained in this admirable essay, it would be necessary to transcribe the whole of it. He shows the remarkable analogy between manganese and metallic oxides. Bergman, in an appendix affixed to Scheele's paper, states his reasons for being satisfied that it is really a metallic oxide. Some years afterwards, Assessor Gahn succeeded in reducing it to the metallic state, and thus dissipating all remaining doubts on the subject.

4. In 1775 he gave a new method of obtaining benzoic acid from benzoin. His method was, to digest the benzoin with pounded chalk and water, till the whole of the acid had combined with lime, and dissolved in the water. It is requisite to take care to prevent the benzoin from running into clots. The liquid thus containing benzoate of lime in solution is filtered, and muriatic acid added in sufficient quantity to saturate the lime. The benzoic acid is separated in white flocks, which may be easily collected and washed. This method, though sufficiently easy, is not followed by practical chemists, at least in this country. The acid when procured by precipitation is not so beautiful as what is procured by sublimation; nor is the process so cheap or so rapid. For these reasons, Scheele's process has not come into general use.

5. During the same year, 1775, his essay on arsenic and its acid was also published in the Memoirs of the Stockholm Academy. In this essay he shows various processes, by means of which white arsenic may be converted into an acid, having a very sour taste, and very soluble in water. This is the acid to which the name of arsenic acid has been since given. Scheele describes the properties of this acid, and the salts which it forms, with the different bases. He examines, also, the action of white arsenic upon different bodies, and throws light upon the arsenical salt of Macquer.

6. The object of the little paper on silica, clay, and alum, published in the Memoirs of the Stockholm Academy, for 1776, is to prove that alumina and silica are two perfectly distinct bodies, possessed of different properties. This he does with his usual felicity of experiment. He shows, also, that alumina and lime are capable of combining together.

7. The same year, and in the same volume of the Stockholm Memoirs, he published his experiments on a urinary calculus. The calculus upon which his experiments were made, happened to be composed of uric acid. He determined the properties of this new acid, particularly the characteristic one of dissolving in nitric acid, and leaving a beautiful pink sediment when the solution is gently evaporated to dryness.

8. In 1778 appeared his experiments on molybdena. What is now called molybdena is a soft foliated mineral, having the metallic lustre, and composed of two atoms sulphur united to one atom of metallic molybdenum. It was known before, from the experiments of Quest, that this substance contains sulphur. Scheele extracted from it a white powder, which he showed to possess acid properties, though it was insoluble in water. He examined the characters of this acid, called molybdic acid, and the nature of the salts which it is capable of forming by uniting with bases.

9. In the year 1777 was published the Experiments of Scheele on Air and Fire, with an introduction, by way of preface, from Bergman, who seems to have superintended the publication. This work is undoubtedly the most extraordinary production that Scheele has left us; and is really wonderful, if we consider the circumstances under which it was produced. Scheele ascertained that common air is a mixture of two distinct elastic fluids, one of which alone is capable of supporting combustion, and which, therefore, he calls empyreal air; the other, being neither capable of maintaining combustion, nor of being breathed, he called foul air. These are the oxygen and azote of modern chemists. Oxygen he showed to be heavier than common air; bodies burnt in it with much greater splendour than in common air. Azote he found lighter than common air; bodies would not burn in it at all. He showed that metallic calces, or metallic oxides, as they are now called, contain oxygen as a constituent, and that when they are reduced to the metallic state, oxygen gas is disengaged. In his experiments on fulminating gold he shows, that during the fulmination a quantity of azotic gas is disengaged; and he deduces from a great many curious facts, which are stated at length, that ammonia is a compound of azote and hydrogen. His apparatus was not nice enough to enable him to determine the proportions of the various ingredients of the bodies which he analyzed: accordingly that is seldom attempted; and when it is, as was the case with common air, the results are very unsatisfactory. He deduces from his experiments, that the volume of oxygen gas, in common air, is between a third and a fourth: we now know that it is exactly a fifth.

In this book, also, we have the first account of sulphuretted hydrogen gas, and of its properties. He gives it the name of stinking sulphureous air.

The observations and new views respecting heat and light in this work are so numerous, that I am obliged to omit them: nor do I think it necessary to advert to his theory, which, when his book was published, was exceedingly plausible, and undoubtedly constituted a great step towards the improvements which soon after followed. His own experiments, had he attended a little more closely to the weights, and the alterations of them, would have been sufficient to have overturned the whole doctrine of phlogiston. Upon the whole it may be said, with confidence, that there is no chemical book in existence which contains a greater number of new and important facts than this work of Scheele, at the time it was published. Yet most of his discoveries were made, also, by others. Priestley and Lavoisier, from the superiority of their situations, and their greater means of making their labours speedily known to the public, deprived him of much of that reputation to which, in common circumstances, he would have been entitled. Priestley has been blamed for the rapidity of his publications, and the crude manner in which he ushered his discoveries to the world. But had he kept them by him till he had brought them to a sufficient degree of maturity, it is obvious that he would have been anticipated in the most important of them by Scheele.

10. In the Memoirs of the Stockholm Academy, for 1779, there is a short but curious paper of Scheele, giving an account of some results which he had obtained. If a plate of iron be moistened by a solution of common salt, or of sulphate of soda, and left for some weeks in a moist cellar, an efflorescence of carbonate of soda covers the surface of the plate. The same decomposition of common salt and evolution of soda takes place when unslacked quicklime is moistened with a solution of common salt, and left in a similar situation. These experiments led afterwards to various methods of decomposing common salt, and obtaining from it carbonate of soda. The phenomena themselves are still wrapped up in considerable obscurity. Berthollet attempted an explanation afterwards in his Chemical Statics; but founded on principles not easily admissible.

11. During the same year, his experiments on plumbago were published. This substance had been long employed for making black-lead pencils; but nothing was known concerning its nature. Scheele, with his usual perseverance, tried the effect of all the different reagents, and showed that it consisted chiefly of carbon, but was mixed with a certain quantity of iron. It was concluded from these experiments, that plumbago is a carburet of iron. But the quantity of iron differs so enormously in different specimens, that this opinion cannot be admitted. Sometimes the iron amounts only to one-half per cent., and sometimes to thirty per cent. Plumbago, then, is carbon mixed with a variable proportion of iron, or carburet of iron.