Popular Science Monthly/Volume 31/October 1887/Sketch of Karl Wilhelm Scheele
|SKETCH OF KARL WILHELM SCHEELE|
THE life of Scheele affords a most conspicuous example in the history of science of a worker who has accomplished great things with the most limited resources. "We stand astonished," said Professor Clève, in his oration at the celebration of the one-hundredth anniversary of the chemist's death—from, which we have derived most of the materials for this sketch—"that a man who only reached his forty-third year should have been able, during his short life, always tormented by material wants, to have arrived, by means restricted and inconvenient, at results which have had so mighty an influence on chemistry." Dumas, comparing him with Lavoisier and Priestley, has said of him that "brought up in a pharmacy, poor and modest, unknown to every one, and hardly knowing himself, inferior to the former but superior to the latter, vanquishing Nature by the force of patience and genius, he snatched her secrets from her and assured an eternal fame for himself."
Karl Wilhelm Scheele was descended from an old family of German origin, and was born at Stralsund, Sweden, December 9 or 19 (authorities differ), 1742. He gave no particular promise in childhood, but was considered "slow," and only moderately intelligent. He took no part in the sports of his brothers and sisters, but amused himself with making all sorts of little objects, and would appear greatly pleased when any of his devices proved successful. His instruction began early at home, and he was at a later period given the usual course at the gymnasium in Stralsund. He became interested in pharmacy through the influence of two friends of the family; and, when fourteen years of age, he was entered as an apprentice with Banch, a pharmacist of Gothenburg, where he soon found himself at home. A friend suggested to him to study chemistry, and his real vocation was revealed to him by the reading of the works of Neumann. From these he advanced to the works of Lémery, of Stahl, the author of the theory of phlogiston, and of Kunkel, the discoverer of phosphorus. He used to repeat secretly at night the experiments he read about in these books, and thus accustomed himself early to do the works of the masters over again with the most scanty and imperfect materials.
After six years of apprenticeship and two years longer of residence in Gothenburg, Scheele became engaged at Malmö, with the pharmacist Kjellström, who, having himself a taste for experimental chemistry, could sympathize with him. He spent his spare money in buying books upon this science; and it was during his residence here that he made the researches on the Sal acetosellæ that led up to the discovery of oxalic acid. He sent a memoir on this subject to the Academy of Sciences at Stockholm, which Bergman, to whom he intrusted it, withheld, because, he said, it contained nothing new. In 1768 he obtained a place in a pharmacy at Stockholm, where he was not allowed any part in laboratory-work. He would make experiments, nevertheless, and so he studied from the windows of the shop the effects of sunlight upon different bodies. He made himself known, too, at Stockholm as a skillful chemist, and formed friendships with the distinguished scientific men of the time. In 1770 he removed to Upsala, where he was installed director of the laboratory-work in a pharmacy, with permission to continue his own experiments.
Forbern Bergman was then Professor of Chemistry in the University of Upsala, and the two men were soon brought into association. Scheele's master had remarked that, on exposing melted saltpeter to a continuous heat, a salt is developed which, on adding acetic acid, gives out red vapors. Neither the chemist Bergman nor the mineralogist Gahn could explain the phenomenon. Scheele had an explanation. He said that the heated saltpeter absorbed phlogiston (is reduced, as we would have it), and gave the salt of a new acid (nitrous acid), which is weak, and can be expelled by acetic acid. Gahn told Bergman of this explanation, and he sought an introduction to the young pharmacist. Thus was laid the foundation of a lasting friendship and co-operation between the two.
In 1775 Scheele obtained the direction of the pharmacy of Köping, whose proprietor had just died, leaving the concern to his widow. This gave him a more comfortable subsistence than he had enjoyed before, although his task in keeping the establishment in good condition and paying up its debts was hard enough. Yet he wrote to one of his friends at about this time: "You may think, perhaps, that material cares are going to absorb me, and take me away from experimental chemistry. Not at all! That noble science is my ideal. Be patient, and you will soon have something new to learn." He was much annoyed about six months afterward by some one coming to buy the pharmacy, and offers of other positions came to him from every side, among them an offer of the superintendency of a distillery, and invitations to Stockholm, Berlin, and London, with salaries that would have been tempting to common men. But the people of Köping said that they would have no pharmacist but Scheele; and he declined all the invitations, saying: "I can not do more than eat my meat; if I can do that at Köping, I need not seek it elsewhere"; and, in reference to an offer which had been made to him from Berlin: "After mature reflection, I decline it. I lack considerably of being as far advanced in chemistry as such a position requires, and I am persuaded that I shall find my daily bread even at Köping."
During his residence at Köping he only gave himself a single vacation, when he went to Stockholm to attend a meeting of the Swedish Academy of Sciences, of which he had been elected a member in 1775. It was the only meeting of the Academy he ever attended, although nearly all of his papers were published in its proceedings. Bergman presided on that day, and received Scheele in the name of the Academy, addressing him in terms of warm eulogy. It was on this occasion that Scheele read his paper on the preparation of calomel. He had just passed his examination as a pharmacist, and received an authorization, free of charge in consideration of his services, to keep the shop at Köping. Bergman, in the same year, secured for him a pension of one hundred riksdalers to encourage and assist his investigations in chemistry, which was continued till his death.
Scheele had now before him the prospect of an easier future. But, although he had never before been ill, he had an attack of gout toward the end of 1775. He nevertheless continued his studies. In February, 1786, he sent to the Academy of Sciences his memoir on gallic acid. In the same month he was attacked with phthisis; and this disease ended with his death on the 21st of May of that year, two days after he had married the widow of his predecessor in the pharmacy.
Scheele was a man of medium stature and vigorous constitution, and was as modest as he was deservedly famous. Thus he wrote to a friend on the occasion of his being elected to the Academy of Turin: "I really believe they think that I am one of the greatest chemists of the time, and they might make me proud. If they keep on in this way, I might come to think I had as much experience and genius as Macquer and Bergman. But I believe, in truth, that those worthy men have more knowledge in their fingers than I have in my head." His education was not extensive, but he had been accustomed from his youth to think independently and without prejudice, and to verify his conclusions, and never to believe any assertion in chemistry till he had personally tested its validity.
There were no grand, elaborately furnished laboratories in those days, and nearly all the great chemists who did so much to put the science on a firm foundation began their work in pharmacists' shops. Scheele's apparatus was of the most simple character, and included a few retorts, common bottles and flasks, and, for experiments on gases, bladders. To collect a gas, he fastened the bladder tightly to the neck of the retort, in which the chemicals for the development of the gas had been placed. If he had to deal with such a gas as nitrous oxide, he saw that the interior of the bladder was well imbued with oil. He usually employed wooden tubes instead of glass ones, lining their interior with a goose-quill. It would be discouraging to a young chemist of to-day to be limited to such apparatus; but Scheele made up for what was wanting in his tools by his remarkable faculty of observation, perseverance, and keenness of discernment. In his experiments he observed all of the slightest details, and went so near to the bottom of things that he left very little for others to discover in any of the work that he did.
Scheele's scientific labors were performed in different fields of chemistry—general, inorganic, organic, and physiological. The "Treatise on Air and Fire" was written in 1775, and published in German in 1777; was translated into English in 1780, and into French in 1781. It contained many facts of great value, together with theories on the nature of combustion, fire, light, and heat, which can have now only historical importance. His researches on the subject, although they were parallel with those of Priestley, and although Priestley anticipated him in the discovery of oxygen, were conducted without any knowledge of what the English chemist was doing. Scheele showed in his treatise, from numerous simple and ingenious experiments, that air is composed of two gases, in a proportion, as he calculated, of about three to one; and he described the special properties of oxygen and nitrogen, as we know them, with their effects on combustion and on animal and plant life.
From experiments with "black magnesia," or the binoxide of manganese and saltpeter, now familiar to all students, Scheele deduced the theory that heat was a combination of phlogiston and oxygen, while combustion was the combination of the oxygen of the air with the phlogiston of the combustible body, resulting in the formation of the compound above named, or heat. Light was also a combination of oxygen and phlogiston, but richer in phlogiston than heat. The different kinds of light were different combinations of oxygen and phlogiston—an assertion which was based upon the fact that violet light exercises a stronger decomposing influence on the chloride of silver than does light of the other colors. Thus Scheele was the discoverer of the fact which is the basis of photography. He found that fluor-spar became phosphorescent when heated moderately, but not when heated to incandescence. This was because the mineral contains phlogiston, which, under a moderate heating, unites with the heat and forms light; but when heat is applied to the degree of incandescence, the phlogiston is all taken away and light can not be formed.
Hydrogen, or inflammable air, as it was then called, he regarded as composed of phlogiston and heat. But after Lavoisier, Cavendish, and Priestley had shown that water is produced by the combustion of hydrogen, and hydrogen is formed by passing the vapor of water over incandescent iron, Scheele changed his theory of oxygen, and assumed that it was composed of a saline principle of water and phlogiston; of these components, the former gave heat with phlogiston, and water caused an increase in the weight of the burned body. These theories attracted much attention at the time; but they are no part of science, for they were quickly dispelled by the publication of Lavoisier's more correct views on combustion. But the facts which Scheele sought to explain by them—nearly all his own discoveries—remain, valuable gifts to chemistry.
His experiments with fluor-spar, carried on in the course of his investigations on light, led to the discovery of hydrofluoric acid, and its property of acting on glass. In the course of three years' researches on black magnesia, or the binoxide of manganese, which M. Clève suggests may have been the most important that he made, he discovered that the basis of the mineral was a new fundamental body, manganese; that it contained, as an impurity, a new earth, baryta, and that when it was treated with muriatic acid another new substance was evolved, chlorine. Further experiments with the last substance revealed its bleaching qualities, which have been so extensively applied in the arts. Finding that the presence of white arsenic helped the solution of the oxide of manganese in acids, he experimented with that body, and discovered the more important arsenical compounds. Scheele discovered that phosphorus was the cause of cold-shortness in iron, and showed that argillaceous earth was distinct from silicious earth, and not an acid-worked modification of it, as had been supposed. He experimented with plumbago, and found that it was "a kind of mineral sulphur or carbon, composed of carbonic acid and a large quantity of phlogiston," or, as we would express it, of carbon, and showed that it was the insoluble substance that occurred in cast-iron, thus opening the way to the further researches that have been made in the differences between iron, cast-iron, and steel, which, still under prosecution, lie at the foundation of our greatest industries. Connected with this investigation, on account of the resemblance of the minerals to graphite, were his researches in molybdenum and in wolfram. The last resulted in the discovery of the metal tungsten, for which the name Scheelium has been proposed.
Very little was known of organic compounds in Scheele's time. It is one of his great titles to merit that he first opened the way to the rich field of the fruitful and enriching discoveries that distinguish the medical and industrial chemistry of our day. The first in order of his researches in this line is his memoir on Prussian-blue, which well illustrates the readiness with which, bringing his extraordinary penetration to bear, he was able to arrive at the truth. In the course of his research he obtained a colorless liquid, which he described as "a substance having a curious odor, but not disagreeable, with a taste somewhat like that of sugar, which heated the mouth slightly and provoked coughing." He little imagined that he had in his hands one of the deadliest poisons known, prussic acid; and we shudder when we think how near it might have come to making an end of him. His researches on the different species of alcohol, described in 1782, indicate that he obtained aldehyde, a substance which has since been the starting-point for numerous important combinations, but of which the discovery is attributed to Liebig, in 1835; he appears also to have encountered chloral in his researches.
The preparations made in his shop led Scheele, in 1783, to the discovery of glycerine, which was at first called Scheele's sweet principle of oils. Boiling oxide of lead with water and oils, he obtained a plaster which he called a kind of hard soap, and which was not soluble in water. Examining the liquid which was left, he observed glycerine.
In a memoir relative to a new method of preserving vinegar (1782), Scheele showed that further change could be prevented by bringing the vinegar to the boiling-point. Scheele was the first to examine the substances which give an acid taste to fruits and plants. To this order belongs his examination of the "salt of sorrel." He also, in one of bis earlier scientific labors, isolated tartaric acid, and introduced the method by which numerous other organic acids have since been separated. In 1784 he discovered citric acid in the lemon, gooseberry, and other fruits, and malic acid in the gooseberry and in fruits generally; and shortly before his death he produced gallic acid, or "salt of gall-nuts," from which he distilled pyrogallic acid, which has been found useful in photography. He first found benzoic acid, saccharic acid, and mucic acid. Examining what was called rhubarb-earth, in 1784, he found it to be composed of oxalate of lime, and from this proceeded to show that that substance is generally present in roots and bark.
In animal chemistry, he examined the concretions of urinary calculus, discovered uric acid, observed its connection with intermittent fevers, and prepared alloxane and cyanuric acid. In 1780 he investigated the phenomena of the curdling of milk, and speculated as to its cause, and in this research discovered lactic acid.
Scheele's nomination as member of the Royal Academy of Sciences, in 1775, is said to have been the only public mark of distinction he received in his native land. He was elected to the Society of Naturalists in Berlin, in 1778; and of the Academy of Sciences of Turin, in 1780, in the presence of his king, Gustavus III. His Majesty, it is said, had not heard much of Scheele before this, and was a little astonished, on hearing the eulogies passed upon the newly-elected member, to hear what a great man he had in his states. He was sorry that he had done nothing for him, and decided to make amends; he would confer an order upon him. The minister to whom he gave his directions was puzzled, for he, too, did not know Scheele. The order was conferred—but upon another Scheele than the chemist!
Scheele's collected works were published at Leipsic, in Latin, in 1788-'89, and in German in 1793. His papers in the Royal Academy have been translated into English by Thomas Beddoes, and are published under the title of "The Chemical Essays of C. W. Scheele."
On the 21st of May, 1886, the one-hundredth anniversary of Scheele's death, the people of Köping held an imposing celebration in memory of the man who had distinguished their town by making it the chosen home of one of the founders of the modern science of chemistry; and the representatives of science in Sweden, Germany, France, Switzerland, and other countries, expressed their sympathy in the occasion in appropriate messages.