Pott’s dissertation on bismuth is of considerable value. He collects in it the statements and opinions of all preceding writers on this metal, and describes its properties with considerable accuracy and minuteness. The same observations apply to his dissertation on zinc.
John Theodore Eller, of Brockuser, was born on the 29th of November, 1689, at Pletzkau, in the principality of Anhalt Bernburg. He was the fourth son of Jobst Hermann Eller, a man of a respectable family, whose ancestors were proprietors of considerable estates in Westphalia and the Netherlands. Young Eller received the rudiments of his education in his father’s house, from which he went to the University of Quedlinburg; and from thence to the University of Jena, in 1709. He was sent thither to study law; but his passion was for natural philosophy, which led him to devote himself to the study of medicine. From Jena he went to Halle, and finally to Leyden, attracted by the reputation of the older Albinus, of Professor Sengerd and the celebrated Boerhaave, at that time in the height of his reputation. The only practical anatomist then in Leyden, was M. Bidloo, an old man of eighty, and of course unfit for teaching. This induced Eller to repair to Amsterdam, to study under Rau, and to inspect the anatomical museum of Ruysch. Bidloo soon dying, Rau was appointed his successor at Leyden, whither Eller followed him, and dissected under him till the year 1716. After taking his degree at Leyden, Eller returned to Germany, and devoted a considerable time to the study and examination of the mines of Saxony and the Hartz, and of the metallurgic processes connected with these mines. From these mines he repaired to France, and resumed his anatomical studies under Du Verney and Winslow. Chemistry also attracted a good deal of his attention, and he frequented the laboratories of Grosse, Lemery, Bolduc, and Homberg, at that time the most eminent chemists in Paris.
From Paris he repaired to London, where he formed an acquaintance with the numerous medical men of eminence who at that time adorned this capital. On returning to Germany in 1721, he was appointed physician to Prince Victor Frederick of Anhalt Bernburg. From Bernburg he went to Magdeburg; and the King of Prussia called him to Berlin in 1724, to teach anatomy in the great anatomic theatre which had been just erected. Soon after he was appointed physician to the king, a counsellor and professor in the Royal Medico-Chirurgical College, which had been just founded in Berlin. He was also appointed dean of the Superior College of Medicine, and physician to the army and to the great Hospital of Frederick. In the year 1755 Frederick the Great made him a privy-counsellor, which is the highest rank that a medical man can attain in Prussia. The same year he was made director of the Royal Academy of Sciences of Berlin. He died in the year 1760, in the seventy-first year of his age. He was twice married, and his second wife survived him.
Many chemical papers of Eller are to be found in the memoirs of the Berlin Academy. They were of sufficient importance, at the time when he published them, to add considerably to his reputation, though not sufficiently so to induce me to give a catalogue of them here. I am not aware of any chemical discovery for which we are indebted to him; but have been induced to give this brief notice of him, because he is usually associated with Pott and Margraaf, making with them the three celebrated chemists who adorned Berlin, during the splendid reign of Frederick the Great.
Andrew Sigismund Margraaf was born in Berlin, in the year 1709, and acquired the first principles of chemistry from his father, who was an apothecary in that city. He afterwards studied under Neumann, and travelling in quest of information to Frankfort, Strasburg, Halle, and Freyburg, he returned to Berlin enriched with all the knowledge of his favourite science which at that time existed. In 1760, on the death of Eller, he was made director of the physical class of the Berlin Academy of Sciences. He died in the year 1782, in the seventy-third year of his age. He gradually acquired a brilliant reputation in consequence of the numerous chemical papers which he successively published, each of which usually contained a new chemical fact, of more or less importance, deduced from a set of experiments generally satisfactory and convincing. His papers have a greater resemblance to those of Scheele than of any other chemist to whom we can compare them. He may be considered as in some measure the beginner of chemical analysis; for, before his time, the chemical analysis of bodies had hardly been attempted. His methods, as might have been expected, were not very perfect; nor did he attempt numerical results. His experiments on phosphorus and on the method of extracting it from urine are valuable; they communicated the first accurate notions relative to this substance and to phosphoric acid. He first determined the properties of the earth of alum, now known by the name of alumina; showed that it differed from every other, and that it existed in clay, and gave to that substance its peculiar properties. He demonstrated the peculiar nature of soda, the base of common salt, which Pott had called in question, and thus verified the conclusions of Duhamel. He gives an easy process for obtaining pure silver from the chloride of that metal: his method is to dissolve the pure chloride of silver in a solution of caustic ammonia, and to put into the liquid a sufficient quantity of pure mercury; the silver is speedily reduced and converted into an amalgam, and when this amalgam is exposed to a red heat the mercury is driven off and pure silver remains. The usual method of reducing the chloride of silver is to heat it in a crucible with a sufficient quantity of carbonate of potash, a process which was first recommended by Kunkel. But it is scarcely possible to prevent the loss of a portion of the silver when the chloride is reduced in this way. The modern process is undoubtedly the simplest and the best, to reduce it by means of hydrogen. If a few pieces of zinc be put into the bottom of a beer-glass and some dilute sulphuric acid be poured over it an effervescence takes place, and hydrogen gas is disengaged. Chloride of silver, placed above the zinc in the same glass, is speedily reduced by this hydrogen and converted into metallic silver.
Margraaf’s chemical papers, down to the time of publication, were collected together, translated into French and published at Paris in the year 1762, in two very small octavo volumes, they consist of twenty-six different papers: some of the most curious and important of which are those that have been just particularized. Several other papers written by him appeared in the memoirs of the Berlin Academy, after this collection of his works was published, particularly “A demonstration of the possibility of drawing fixed alkaline salts from tartar by means of acids, without employing the action of a violent fire.” It was this paper, probably, that led Scheele, a few years after, to his well-known method of obtaining tartaric acid, a modification of which is still followed by manufacturers.
“Observations concerning a remarkable volatilization of a portion of a kind of stone known by the names of flosse, flusse, fluor spar, and likewise by that of hesperos: which volatilization was effectuated by means of acids.” Pott had already shown the value of fluor spar as a flux. Three years after the appearance of Margraaf’s paper, Scheele discovered the nature of fluor spar, and first drew the attention of chemists to the peculiar properties of fluoric acid.
In France, in consequence chiefly of the regulations established in the Academy of Sciences, in the year 1699, a race of chemists always existed, whose specific object was to cultivate chemistry, and extend and improve it. The most eminent of these chemical labourers, after the Stahlian theory was fully admitted in France till its credit began to be shaken, were Reaumur, Hellot, Duhamel, Rouelle, and Macquer. Besides these, who were the chief chemists in the academy, there were a few others to whom we are indebted for chemical discoveries that deserve to be recorded.
René Antoine Ferchault, Esq., Seigneur de Reaumur, certainly one of the most extraordinary men of his age, was born at Rochelle, in 1683. He went to the school of Rochelle, and afterwards studied philosophy under the Jesuits at Poitiers. Hence he went to Bourges, to which one of his uncles, canon of the holy chapel in that city, had invited him. At this time he was only seventeen years of age, yet his parents ventured to intrust a younger brother to his care, and this care he discharged with all the fidelity and sagacity of a much older man. Here he devoted himself to mathematics and physics, and he soon after went to Paris to improve the happy talents which he had received from nature. He was fortunate enough to meet with a friend and relation in the president, Henault, equally devoted to study with himself, equally eager for information, and possessed of equal honour and integrity, and equally promising talents.
He came to Paris in 1703. In 1708 he was admitted into the Academy of Sciences, in the situation of élève of M. Varignon, vacant by the promotion of M. Saurin to the rank of associate.