Theodore William Richards
Richards, Theodore William
RICHARDS, THEODORE WILLIAM
(b. Germantown, Pennsylvania, 31 January 1868; d. Cambridge, Massachusetts, 2 April 1928) chemistry.
Richards was the son of gifted parents: William Trost Richards, a noted painter of seascapes, and Anna Matlack Richards, a Quaker author and poet. Because his mother felt that public education was geared to the slowest student in the class, Richards received his elementary and secondary schooling at home. At the age of six he became friendly with Josiah Parsons Cooke, Jr., professor of chemistry at Harvard University, who by showing the child Saturn through a telescope, awakened Richards’ interest in science. By the time he joined the sophomore class at Haverford College at the age of fourteen, his only formal education had been attendance at some chemistry lectures at the University of Pennsylvania. In June 1885 he graduated at the head of his class with a degree in chemistry; and, eager to study under Cooke, he entered the senior class at Harvard the following fall. The youngest member of the class, Richards graduated in June 1886 with highest honors in chemistry.
As a graduate student at Harvard, Richards undertook—under Cooke’s direction—the difficult laboratory problem of accurately determining the composition of water in order to obtain the relative weights of hydrogen and oxygen. He found that the ratio 1:15.96 disproved the validity of the statement (Prout’s hypothesis) that atomic weights of the elements are integer multiples of that of hydrogen. In this investigation he learned the techniques that he later used so skillfully in his own laboratory: care, precision, and especially patience. In 1888 he received the doctorate; and because of the merit of his dissertation, he was awarded the Parker fellowship, which enabled him to spend a year abroad making many important professional friendships.
Upon his return in the autumn of 1889, Richards joined the Harvard faculty as an assistant in quantitative analysis and never severed his connection with the university (although he spent one year at the University of Berlin as an exchange professor in 1907). Promotions came rapidly for Richards: instructor in 1891; assistant professor in 1894; and full professor in 1901 (this last promotion coming as a result of his being offered the chair of physical chemistry at the University of Göttingen). He was chairman of the chemistry department from 1903 until 1911 and director of the Wolcott Gibbs Memorial Laboratory from its opening in 1912 until his death in 1928. Holding the prestigious Erving professorship of chemistry from 1912 until 1928, he remained active in teaching and research until less than a month before his death. Richards married Miriam Stuart Thayer, the daughter of a professor at the Harvard Divinity School, in 1856; they had three children.
Richards’s best-known studies were his determinations of the atomic weights of twenty-five elements, including those used to determine virtually all other atomic weights. For this work he was awarded the 1914 Nobel Prize in chemistry, the first chemist in the United States to be so honored. He also received the Davy Medal of the Royal Society (1910), the Faraday Medal of the Chemical Society (1911), and the Willard Gibbs Medal of the American Chemical Society (1912), among numerous awards, honorary degrees, and memberships in foreign societies. About one-half of his nearly three hundred published papers deal with atomic weights.
When Richards began publishing his work in 1887, the accepted values of atomic weights were based upon those determined by Stas in the 1860’s. Stas’s research was characterized by lengthy and careful procedures utilizing large quantities of materials and achieved an accuracy far exceeding that of earlier workers. These values were so well received that until 1905 no investigator seriously questioned them nor attempted to check his work.
After accurately determining the oxygen-hydrogen ratio, Richards turned to the atomic weights of several metallic elements. These early studies showed that copper from widely separated sources has exactly the same atomic weight. The studies also verified that the atomic weight of cobalt is greater than that of nickel, although cobalt precedes nickel in the periodic table. In his studies of the alkaline-earth strontium, he developed two important experimental devices: a bottling apparatus for transferring weighed samples without contact with moist air, and a nephelometer for accurately determining the amount of silver halide precipitate causing turbidity in samples Most of Richard’s analyses involved the precipitation of silver halide from solutions of halide salts of the desired element.
By 1905 Richards had become aware of serious errors in Stas’s classical studies. theory of precipitation had progressed far enough for him to see that his predecessor had neglected the slight but important solubility of silver chloride, that he had added solid silver nitrate to his solutions of metal halide salts (which caused silver nitrate to be included as an impurity in the precipitate), and that he had used such large quantities that impure samples dramatically increased the errors. Consequently, the Harvard group redetermined the atomic weights of several major elements previously studied by Stas: silver, nitrogen, chlorine, sodium, and potassium. In all cases Richards’ work produced significant changes in the accepted values.
Richards’ other major contribution to the field of atomic weights was a comprehensive study of the atomic weight of radioactivity lead from uranium minerals. Although radioactivity was actively studied in many laboratories and the isotope concept had been suggested in 1907, the only experimental verification that chemically identical substances could have different atomic weights came from the analytical laboratory. The study of Richards and Lembert, published in 1914, was one of the first confirmations that the lead from radioactive minerals does have a different atomic weight from normal lead. Until Aston developed the mass spectrograph in 1919, tedious chemical analysis continued to provide the only experimental confirmation of various isotopes.
Richards was indirectly responsible for determining the atomic weights of thirty additional elements, since they were investigated by two of his former students, Gregory Baxter at Harvard and Otto Hönigschmid at Munich. Baxter became the first Richards professor of chemistry, a chair endowed in Richards’ honor in 1925.
Although best known for his atomic weight studies, Richards directed a vigorous research program in thermochemistry and electrochemistry. He became interested in these subjects in 1895 when, upon the death of Cooke, Harvard sent him to visit the laboratories of Wilhelm Ostwald at Leipzig and Walther Nernst at Göttingen in order to improve his qualifications to teach physical chemistry. Many of his later investigations were a direct result of his theory of the compressible atom, an attempt to explain physically the variation of the constant “b” in van der Waals’s equation of state. He proposed that an atom had a changeable volume, the magnitude of which depends upon its chemical state. Thus the volume of a potassium atom in its chloride salt is much less than that of a free potassium atom. Although the hypothesis was never adopted by other investigators, and although Richards spent much of his last ten years unsuccessfully trying to place the theory upon a firm mathematical foundation, his efforts led to the accurate determination of the physical constants of many elements and compounds. In nearly thirty publications on the subject, he attempted to correlate compressibilities of substances with their densities, surface tensions, heats of reaction, and other properties. As a part of this study in 1902, while investigating the behavior of galvanic cells at low temperatures, he approached the discovery of the principles enunciated by Nernst in 1906 as the third law of thermodynamics.
While measuring thermodynamic values in his compressibility studies, Richards became aware of certain shortcomings in the calorimetric methods then in use, especially the need to apply a complex cooling correction to the calculation of his results, on account of heat transfer from the reaction vessel to the calorimeter jacket. Seeking to eliminate the problem, Richards, Lawrence J. Henderson, and George Shannon Forbes in 1905 devised an adiabatic calorimeter, in which the jacket temperature could be adjusted to that of the reaction vessel. Although a similar calorimeter had actually been invented in 1849 by the Frenchman Charles C. Person, Richards and his colleagues were the first to use such a calorimeter extensively.
Using continually improved versions of this calorimeter, Richards published sixty papers on thermochemistry—many of them containing data that are still standard among the accepted values in handbooks of physical constants. Notable in this work is an extensive study by Richards, Allan W. Rowe, and Frank T. Gucker on the heats of dilution of metals in acids; the specific heats of acids, bases, and salts; and the heats of neutralization of strong and weak acids and bases. Richards’ series of electrochemical studies includes the observation that “Faraday’s law is not a mere approximation, but is rather … among the most precise … laws of nature.” The Harvard group also carried out an extensive investigation of the electrical and thermodynamic properties of amalgams.
During his years as a member of the faculty, Richards created at Harvard a mecca for physical and analytical chemical research. Over sixty young men studied with him and became renowned chemists in their own right. Gilbert N. Lewis, Farrington Daniels, Arthur B. Lamb, Gregory P. Baxter, James B. Conant, Hobart H. Willard, and Otto Hönigschmid among others were products of the “Richards school.” Richards was also noted for the excellence of his courses in physical chemistry. Although he distrusted mathematics and taught a much less rigorous approach than is presently offered to undergraduates, he liked to include historical material. The first introduction to the history of science for Conant, Henderson, and Frederick Barry came from Richards’ lectures.
I. Original Works. No comprehensive bibliography of Richards’ works has ever been published; however, a list of Richards’ 292 published papers is in Sheldon J. Kopperl, The Scientific Work of Theodore William Richards, Ph.D. diss., University of Wisconsin, (Madison, 1970), 333–359.
On the composition of water, see “The Relative Values of the Atomic Weights of Hydrogen and Oxygen,” in Proceedings of the American Academy of Arts and Sciences, 23 (1887), 149, written with Josiah Parsons Cooke, Jr. On the nephelometer, see “The Nephelometer, an Instrument for Detecting and Estimating Opalescent Precipitates,” in American Chemical Journal, 31 (1904), 235, written with R. C. Wells. On the first redetermination of Stas’s values, see “A Revision of the Atomic Weights of Sodium and Chlorine,” in Journal of the American Chemical Society, 27 (1905), 459, written with R. C. Wells. Richards’ first paper on lead from uranium ores is “The Atomic Weight of Lead of Radioactive Origin,” ibid., 36 (1914), 1329, written with Max E. Lembert. The low-temperature work with galvanic cells is “The Significance of Changing Atomic Volume. III,” in Proceedings of the American Academy of Arts and Sciences, 38 (1902), 291.
The adiabatic calorimeter is first discussed in “The Elimination of Thermometric Lag and Accidental Loss of Heat in Calorimetry,” ibid., 41 (1905), 1, written with Lawrence J. Henderson and George Shannon Forbes. The remarks on Faraday’s law come from “The Universally Exact Application of Faraday’s Law,” ibid., 38 (1902), 407, written with W. N. Stull. Richards’ only book-length publication is a collection of his early papers on atomic weights, translated into German and published as Experimentelle Untersuchungen über Atomgewichte, 1887–1908 (Hamburg, 1909).
II. Secondary Literature. The only book-length treatment of Richards is Kopperl’s Ph.D diss. cited above. An extensive sketch is Harold Hartley, “Theodore William Richards Memorial Lecture,” in Journal of the Chemical Society (1930), 1930–1968, which summarizes Richards’ work in detail. A recent short study on Richards’ atomic weight investigations is Aaron J. Ihde, “Theodore William Richards and the Atomic Weight Problem,” in Science, 164 (1969), 647–651.
Sheldon J. Kopperl
Theodore William Richards
Theodore William Richards
The American chemist Theodore William Richards (1868-1928) ushered in a new age of accuracy in chemistry by determining the atomic weights of many elements.
Theodore W. Richards was born on Jan. 31, 1868, in Germantown, Pa. His father, William Trost Richards, was a prominent landscape and marine artist; his mother, Anna Matlock Richards, was a poet and a woman of great cultivation. Until he entered college, his education was at home under his mother's direction. At age 14 he entered Haverford College as a sophomore, uncertain whether to become an astronomer or a chemist. He had defective eyesight, however, and by the time of his graduation he had decided on a career in chemistry.
In 1885 Richards entered Harvard as a senior and the following year was granted the bachelor's degree. Two years later he was awarded the doctorate with a dissertation on the atomic weights of hydrogen and oxygen. He won a Harvard grant for a year of travel and study in Europe. On his return to Harvard in 1889, he became an assistant and subsequently an instructor in analytical chemistry.
Atomic Weight Determinations
To Richards, atomic weights were the most fundamental constants in nature, and he associated them with deep questions about the universe. They offered more promise of contributing to the understanding of the universe than any other area of chemistry. By very thorough, painstaking work he published revised atomic weights for copper, zinc, barium, strontium, magnesium, and calcium.
In 1894 Richards introduced two new devices to overcome the two most prevalent sources of error in atomic weight work: the presence of moisture and the loss of traces of precipitate. His bottling apparatus enabled him to fuse, handle, and weigh solids under absolutely dry conditions. His nephelometer (cloud measurer) enabled him to determine traces of unrecovered precipitate by measuring the turbidity of the filtrate.
Along with his research Richards was teaching quantitative analysis. In 1894 he was promoted to assistant professor. Harvard sent him to Germany for a year of training in physical chemistry. On his return from Europe in 1896 he married Miriam Stuart Thayer.
Over the next few years Richards corrected the atomic weights of nickel, cobalt, iron, uranium, and cesium. In every instance his results became the official ones of the International Commission on Atomic Weights. His revision of the atomic weights of J. S. Stas involved correcting for errors in purification, drying, and weighing of materials, and it inaugurated a new era of accuracy. His papers published from 1905 to 1910 exceeded in accuracy any chemical research ever published.
In 1901 Richards was promoted to full professor, and in 1912 he became Erving professor of chemistry and director of the new Wolcott Gibbs Memorial Laboratory (1913), which was the finest chemical laboratory in the world.
By 1913 the study of radioactive decay led to the possibility that an element may have more than one atomic weight. Richards analyzed radioactive samples of lead, and all of his determinations were below the atomic weight of ordinary lead, the lowest being 206.08. He concluded that there was no doubt that uranium transmuted itself into a light variety of lead. Frederick Soddy announced the isotope concept in 1913, and Richards's experiments were the first confirmation of the new theory and the only conclusive evidence for isotopes until the development of the mass spectrograph.
Atomic weights have remained the most frequently required units by chemists in quantitative measurements of all kinds. Richards determined the atomic weights of 25 elements. His students, Gregory Baxter at Harvard and Otto Hönigschmidt at Munich, continued his work and were responsible for 30 additional elements.
Of Richards's almost 300 papers, about one-half deal with atomic weights, the remainder being concerned with several aspects of physical chemistry. He was a leader in introducing this new field into the United States, and his laboratory was a center which prepared a new generation of physical chemists. Richards made investigations in thermochemistry, electrochemistry, and the physicochemical study of the properties of matter. In physical chemistry, as in atomic weights, his work represented an advance in precision and accuracy.
One of Richards's most productive areas of research was thermochemistry. In 1905 he introduced the adiabatic calorimeter to prevent the loss or gain of heat to and from the surroundings. He published over 60 papers on thermo-chemistry and for many years was a pioneer in precision calorimetry.
In 1899 Richards began a study of the atomic volumes and compressibilities of the elements after noting that the constant b occurring in the Van der Waals equation (p + a/V2)(V - b) = RT was not a constant but varied with pressure and temperature. Since b was the space occupied by the molecule, Richards asserted that the concept of the atom as a hard, rigid particle was incorrect. He proposed that atoms were compressible, the forces of affinity and cohesion exerting a compressing effect on atoms resulting in enormous internal pressures. He devised methods to determine the compressibilities of the elements up to 500 atmospheres pressure and tried to correlate this property with the other fundamental properties of the elements in the hope of discovering important relationships. He never completed these studies; nevertheless, his experimental data proved to be invaluable to atomic physics.
His Character and Honors
Richards was primarily an experimentalist of exceptional ability. Yet his measurements were only a means to an end; with them he searched for an understanding of the material structure of the universe.
Richards received many honorary degrees and medals. A Harvard professorship was endowed in his name in 1925. He received the Nobel Prize in chemistry in 1914, the first American chemist to be so honored. He was a man of noble character who made a deep impression on those who met him. The guiding principles of his life he described as "kindliness and common sense." He died on April 2, 1928.
Richards presented his atomic weight research in Determinations of Atomic Weights (1910). In his Nobel Prize lecture, printed in Nobel Foundation, Nobel Lectures: Chemistry, 1901-1921 (1966), he described both his research and his beliefs about the universe. Of the many biographical studies of Richards, the most informative are those in Benjamin Harrow, Eminent Chemists of Our Time (1927); Sir Harold Hartley, Memorial Lectures Delivered before the Chemical Society (3 vols., 1933); and Aaron J. Ihde, Great Chemists (1961). □