Adapted from the Journal of the American Medical Association,
June 29, 1970, vol. 212, no 13, 2258-2259.
C. W. Scheele, the greatest organic chemist of his time and possibly of all times, spent all of his professional years as a practicing apothecary. He was born in Stralsund, Sweden, into a family of German descent (1). His father was a brewer and broker with limited resources, but he provided private schooling followed by Gymnasium training. Scheele was attracted to chemistry early in life and, at the age of 14, began an apprenticeship in Gothenburg in an apothecary shop, the only route at that time to the profession. In addition to fulfilling the duties of an apprentice, Scheele read the best chemical works available, including those of Lemery, Stahl, designer of the phlogiston theory, and Kunkel, discoverer of phosphorus. Also, he repeated with crude and simple equipment selected experiments of the recognized masters.
Scheele's apothecary work was continued in succession in Malmö and Stockholm; while in Upsala in 1770, he was appointed director of laboratory work in a pharmacy. This assignment permitted him to carry on his chemical experiments and to establish scientific liaison with Bergman, professor of chemistry in the University, and Gahn, a noted mineralogist. His final five years were spent in charge of the pharmacy in Koping: there he was sorely troubled with intractable gouty arthritis, a malady to which he made a great chemical contribution.
Scheele's fruitful investigations embraced inorganic, organic, and physical chemistry. Even though the phlogiston theory of combustion prevailed, his remarkable powers of observation and keen discernment overcame the concept which had been an obstacle for almost a century to an understanding of oxidation and reduction. Many of his studies were communicated to the Royal Academy of Science, Stockholm, and through translation became readily available in German, French and English. His greatest monograph, Chemical Treatise on Air and Fire (2), was written in Swedish in 1775, translated into German and published in 1777, and translated into English three years later. The last edition of Scheele's collected works, translated into English and from which the excerpts in this biography were taken appeared in 1931. His discoveries on the nature of combustion were conducted independently and paralleled those of Priestley who anticipated him in the discovery of oxygen, calling it "dephlogisticated air".
Although it had been accepted since the speculations of Aristotle and Galen that air was an element and indivisible, Scheele determined in simple but ingenious experiments that air is composed of two gases in the approximate ratio of three to one. Eventually breaking from the phlogiston theory, Scheele retained the term in the Treatise and assumed heat and light to be combinations of oxygen and phlogiston, each in different proportions. Oxygen was isolated during the ignition of red oxide of mercury, silver carbonate, magnesium nitrate, and potassium nitrate. The gas was recognized by him to be odorless and tasteless and essential to respiration and in the germination of seeds. One of Scheele's experiments was translated as follows:
First Experiment - I mixed so much concentrated oil of vitriol with finely powdered manganese that it became a stiff magma. I distilled this mixture from a small retort on the open fire. In place of a receiver I made use of a bladder, empty of air, and in order that the vapours which might pass over should not attack the bladder, I poured into it some milk of lime. As soon as the bottom of the retort became red hot, an air passed over which gradually expanded the bladder. This air had all the properties of a pure fire air.
Summaries of many of Scheele's original observations in inorganic and organic chemistry were enumerated by Dobbin in the translator's introduction to "The Collected Papers of Carl Wilhelm Scheele" (3).
These include the independent discovery of oxygen and the discovery of chlorine and of barium compounds; also the observations of the solubility of manganous carbonate in water containing dissolved carbon dioxide; of the dark colour of precipitated manganous hydroxide as due to the air dissolved in the solutions employed; of the formation of manganate and permanganate; of the effect of manganese dioxide in removing the green colour, due to iron, from ordinary bottle glass; of the production of mercuric cyanide in solution by boiling a mixture of Prussian blue and mercuric oxide with water; of the liberation of hydrogen by the interaction of iron with water only; of the varying effects of the different parts of the solar spectrum on silver chloride; of the different effects produced by the exposure to direct sunlight of two thermometers, otherwise similar but of which the one contained red-coloured and the other colourless spirit; and of the absorption of gases by charcoal.
Amongst numerous observations by Scheele which are of analytical importance, there are those concerned with the recognition of dissolved oxygen in water by means of ferrous sulphate and potassium carbonate; of hydrocyanic acid in a mixture with air by suspending in the air for some time a paper strip which has been moistened successively with ferrous sulphate and alkali-metal hydroxide solutions, and afterwards treating the strip with hydrochloric acid; of the presence of manganese in plant ash by fusing the ash with potassium nitrate; and of uric acid in calculus by heating the latter with nitric acid.
DISCOVERY OF URIC ACID
In the discovery of uric acid, the initial observations were made on a collection of bladder calculi, which were pulverized and their properties studied with various physical and chemical agents. The previously unknown concrete or calculus acid was found in all urines and in higher concentrations in the sick than in the healthy (4).
Pure water dissolves the calculus completely, but much water is required for this. When five ounces of water are poured upon eight grains of finely powdered calculus, and boiled for a short time, it is dissolved. The solution makes tincture of litmus red, and does not precipitate lime water. When it cools, the greater part of the calculus separates from it in the form of fine crystals.
Finally I have found some calculus dissolved in all urine, even in that of children. When four kannes of clear and fresh urine are evaporated till only two ounces of it remain, a fine powder is deposited on cooling, a part of which adheres firmly to the glass vessel. It is dissolved quite easily, without heat, by a few drops of caustic lye and possesses besides all the properties of calculus. The sediment which deposits itself like brick-dust in the urine of those who have the ague, is of the same nature.
In accordance with the experiments cited, all urine thus contains, besides the previously known substances (which are sal ammoniac, common salt, digestive salt, Glauber's salt, microcosmic salt, prelate salt, and an oily extract), a previously unknown concrete acid, or calculus, and animal earth. It is remarkable that the urine of sick persons is more acid and contains more animal earth than that of the healthy.
TRIBUTE TO CARL WILHELM SCHEELE
Scheele led a simple life, completely absorbed in his chemical studies, His genius was recognized at home and abroad, but always he preferred to be known as an "apothecary" and so signed his documents. When he was 32 years of age, he was elected to the Swedish Academy of Science and received a life annuity in recognition of his work. Several unaccepted offers to study and teach came from abroad, as well as membership in the Society of Naturalists in Berlin in 1778 and the Academy of Sciences of Turin in 1780. Monuments in Scheele's honor have been erected in Stockholm and Köping; his country and international learned societies have honored him posthumously.
- Urdang, G: Carl Wilhelm Scheele: A Pictorial Biography. Madison, Wis, American Institute of the History of Pharmacy, 1958.
- Scheele, CW: Chemical Treatise on Air and Fire (Ger), Upsala and Leipzig , M Swederus, 1777.
- Dobbin L: The Collected Papers of Carl Wilhelm Scheele, London, G Bell & Sons, Ltd., 1931.
- Scheele K: Investigations of bladder stones (Swed), Kongl Vetenskaps Acad Handl 37: 327-332, 1776