STOCK, ALFRED

(b. Danzig, West Prussia [now Gdansk, Poland], 16 July 1876; d Aken, Germany, 12 August 1946) chemistry.

The son of a bank executive, Stock received a Gymnasium education in Berlin. He developed an interest in science as a schoolboy and matriculated as a chemistry student at the University of Berlin in 1894. Attracted to Emil Fischer’s institute, he began his doctoral research in 1895 under Oscar Piloty. Following his graduation, magna cum laude, in 1899. Stock spent a year in Paris as an assistant to Moissan. On 21 August 1906 he married Clara Venzky, who bore him two daughters. Stock pioneered in the development of the chemistry of the boron and silicon hydrides, developed the chemical high-vacuum technique, held numerous high positions in chemical organizations and educational institutes, and made important contributions to chemical education and nomenclature. Some of his work had important technological applications. His intensive investigations into the pathology and detection of mercury were prompted by his desire to spare others the suffering he endured from the effect of chronic mercury poisoning.

Stock devoted the first nine years (1900–1909) of his professional career at the University of Berlin to the preparation and characterization of the modifications of phosphorus, arsenic, and antimony, and their compounds with hydrogen, sulfur, and nitrogen. He identified an unstable yellow form of antimony, and a new polymeric hydride (P₂H₉) and nitride (P₃N₅) of phosphorus. His research on the phosphorus-sulfur system resolved many ambiguities in the literature and established the existence of three of the four well-established phosphorus sulfides. His study of the kinetics of the decomposition of antimony hydride was a classic example of an autocatalytic, heterogeneous decomposition.

In July 1909, Stock was appointed to organize and direct the new Inorganic Chemistry Institute at Breslau, where he began an experimental program inspired by the belief that boron ought to have an extensive and diverse chemistry analogous to that of the hydrocarbons. Previous attempts, by Ramsay and others, to produce hydroboranes by the reaction of magnesium boride with mineral acids had led to incomplete and erroneous conclusions because of the difficulty of isolating and characterizing the small amounts of volatile, unstable, and highly reactive compounds formed. The problem was complicated by the presence of silanes and other gases in the reaction mixture. Stock devised a high-vacuum apparatus that permitted the quantitative manipulation and fractionation of small amounts of gaseous and volatile materials in the absence of air and lubricating greases. He soon established the existence of three boranes–B₂, H₆ ,B₄H₁₀ B₁₀H₁₄–and produced evidence for others that later proved to be B₅H₉ and B₆H₁₀.

In 1916 Stock moved to the Kaiser Wilhelm Institute in Berlin. During this time he concerned himself with problems related to the war and to the restoration of German chemistry afterward. His research efforts were devoted primarily to the study of the reactive and volatile silicon hydrides. At the time of Stock’s entry into this field, only SiH₄ had been well characterized. His high-vacuum technique enabled him to purify and characterize Si₂H₆ and two new silanes, Si₃H₈ and Si₄H₁₀, and to establish the existence of Si₅H₁₂ and Si₆H₁₄. Stock prepared numerous halogen derivatives of these compounds that in turn were used to produce many new and interesting compounds, such as siloxanes, silyl amines and amides, and alkyl silanes. Supported by the experimental knowledge obtained through work on the silanes, he prepared very pure samples of B₂H₆ and B₄H₁₀ and isolated B₅H₉ and B₆H₁₀. In 1924 he discovered yet another borane, B₅H₁₁.

Ever since his early postdoctoral years, Stock had suffered from headaches, vertigo, numbness, catarrhs, poor hearing, and ailments of the upper respiratory tract that would not respond to any medical treatment. During 1923 he suffered an almost total loss of memory and hearing. In March 1924, after an unbearable winter, he discovered that his difficulties stemmed from mercury poisoning, caused by prolonged exposure to mercury vapors (several micrograms of mercury per cubic meter) in poorly ventilated laboratories. After a brief rest Stock began a program of research into the analysis and pathology of mercury that continued to the end of his active life. He devised techniques capable of detecting 0.01 microgram of mercury, which he used to determine mercury concentrations in natural materials and common reagents. He examined the modes of ingestion of mercury and traced its path through the body and its accumulation in various organs, often using himself as an experimental subject. He wrote numerous articles warning of the dangers of mercury and suggested precautionary measures.

After his appointment as director of the Chemical Institute at Karlsruhe in October 1926, Stock constructed a model chemical laboratory designed to minimize mercury contamination. Here he determined the genetic relationships between the boranes and developed more effective preparation techniques; studied the reactions of boranes with active metals and prepared compounds that were later recognized as borohydrides, now an important class of reducing agents in organic chemistry; and prepared borazine B₃ N₃H₆, an important inorganic analogue of benzene.

In addition to his hydride research, Stock investigated a number of compounds of carbon with oxygen, sulfur, selenium, and tellurium; introduced many improvements in apparatus, including the mercury valve, automatic Töpler pump, vapor-tension thermometer, zinc arc, and gas buoyancy balance; and devised numerous accessories for the widely used Stock high-vacuum technique. He drew up a system of chemical nomenclature that has been universally adopted by inorganic chemists. Stock perfected an instructional epidiascope that could project chemical demonstrations on a large screen by means of incident or reflected light. Some of his research led to industrial applications: P₄ S₃ was used as a substitute for phosphorus in matches, and P₃ N₅ was used to remove traces of oxygen from incandescent lamps. His technique for the electrolytic preparation of beryllium became the basis for the first commercial production of that metal. His work on silicon helped establish the chemical foundations for the technologically important silicone plastics.

Stock not only opened up two important fields of chemistry but also devised apparatus and techniques of great versatility and exactness that made the achievement possible, and established the associated health hazards and precautionary measures necessary for safety. E. Wiberg described him as punctual, neat, exact, and patient, yet witty and sociable. Although his work stimulated a great deal of theoretical speculation, and in some cases led to practical applications, Stock always remained an experimentalist who was driven by the pure joy of discovery. He placed as little value on speculative opinion as he did on seeking practical applications of his research.

Stock received many honors, including the presidency of both the Verein Deutscher Chemiker (1926–1929) and the Deutsche Chemische Gesellschaft (1936–1938). He was appointed to many major policy committees and represented Germany at several international conferences. His deteriorating health and increasing difficulties with political authorities caused him to retire in October 1936, at the age of sixty. He returned to Berlin, where he continued his research on mercury. By 1940 his movements had become so restricted by the onset of myogelosis (hardening of the muscles) that he was almost completely confined to his home. In May 1943 he gave up his small laboratory, which was needed for war work, and retired to Bad Warmbrunn in Silesia. With Russian cannon rumbling in the distance, he and his wife packed the few belongings they could carry and undertook a grueling train trip to Aken, a small city on the Elbe. Stock died there in obscurity, after a life of great accomplishment and tragic suffering.

BIBLIOGRAPHY

I. Original Works. A complete bibliography of Stock’s 274 publications is in Wiberg (see below). His books include Praktikum der quantitativen anorganischen Analyse (Berlin, 1909), written with Arthur Stähler; Ultra-Strukturchemie (Berlin, 1920); and Hydrides of Silicon and Boron (Ithaca, N. Y., 1933)

II. Secondaery Literature The major biography is E. Wiberg, “Alfred Stock,” in Chemische Berichte, 83 (1950), xix-lxxvi; a short summary of this article is in E. Farber, ed., Great Chemists (New York, 1961), 1423–1432

John E. Frey