Georges entered the École Polytechnique in 1885, having placed first in the competitive entrance examination.
Gallery of Georges Friedel
158 Cours Fauriel, 42023 Saint-Étienne, France
Georges entered the École Nationale des Mines in St. Etienne for a three-year course in 1887. Mallard was his professor of mineralogy, and his father introduced him to research in mineral synthesis.
Georges entered the École Nationale des Mines in St. Etienne for a three-year course in 1887. Mallard was his professor of mineralogy, and his father introduced him to research in mineral synthesis.
Georges Friedel was a French mineralogist and crystallographer. He was also director of the Ecole Nationale des Mines at Saint-Étienne.
Background
Georges Friedel was born on July 19, 1865, in Mulhouse, France. He was the son of the famous chemist Charles Friedel, who taught mineralogy and organic chemistry at the University of Paris and was, at the same time, the curator of the mineralogical collections of the School of Mines. Charles’s father was a banker in Strasbourg. His maternal grandfather was Georges Duvernoy, a co-worker of Cuvier and his successor at the Collège de France. The Friedel family had left their Alsatian home before the Franco-Prussian War. Georges spent his childhood, until the age of fifteen, in Paris, where his parents’ apartment was in the building of the School of Mines. This school was to exert a profound influence on his career.
Education
Georges entered the École Polytechnique in 1885, having placed first in the competitive entrance examination. Upon graduation, he returned to the School of Mines for a three-year course. Mallard was his professor of mineralogy, and his father introduced him to research in mineral synthesis.
As a mining engineer Friedel received an appointment in the French civil service in 1891 and was put in charge of the Moulins district. In 1893 he entered the School of Mines at Saint-Étienne, where he taught courses in assaying, ferrous metallurgy, physics, mineralogy, geology, and the applications of electricity to mining. From 1899 he lectured only on geology and mineralogy, and after he became a director in 1907, he limited himself to mineralogy. Friedel felt strong ties to the Saint-Étienne school and declined several calls from the School of Mines in Paris. But, after World War I, he did accept the chairmanship of the Institute of Geological Sciences at the newly reopened French University of Strasbourg, where his great-grandfather Duvernoy had been the dean of the Faculty of Sciences some eighty-five years before. The return to his liberated Alsace was one of the great joys of his life. For some time before his retirement in 1930, a painful illness prevented Friedel from giving his courses, and his son Edmond substituted for him.
The work of Friedel is remarkable for its diversity. It is essentially crystallographic and mineralogical, but it deals also with petrology, geology, and even engineering and pedagogy.
Jointly with his father, Friedel first published accounts of a number of syntheses produced in a steel tube lined with platinum, at about 500°C. and under high pressure. Synthetic minerals were prepared by letting group I hydroxides and silicates or salt solutions act on mica.
Friedel’s work established the interstitial nature of zeolitic water, which can be replaced by many liquids and gases in the zeolitic “sponge.” He found zeolitic water in compounds other than zeolites.
In 1893 Friedel developed a method for the accurate measurement of path-difference that is based on the restoration of elliptically polarized light to plane polarized light. This method was later applied to the study of stressed glass by R. W. Goranson and L.H. Adams.
In 1904 the law of Bravais, based as it was on speculative considerations, was far from being generally accepted. Friedel established its validity as a law of observation, regardless of theory. Another empirical law enunciated by Fiedel, and shown by Alfred Liénard to be a consequence of the law of Bravais, is the law of mean indices. After 1912, when the structural lattice, which expresses the periodicity of the crystal structure, could be determined by X-ray diffraction, Friedel noted that in many instances it did not coincide with his morphological lattice. This discrepancy, he pointed out, does not diminish but, rather, enhances the value of the morphological lattice, which remains the expression of duly observed facts. Final confirmation of the law of Bravais came with its generalization by J. D. H. Donnay and D. Harker in 1937, after Friedel’s death, when it was found that the effective interplanar spacings depend not only on the lattice mode but also on the glide planes and screw axes in the space group.
In 1905 the Bravais lattice was, structurally speaking, only a hypothesis. Friedel proved its physical reality by noting that irrational threefold axes had never been found in crystals. This fundamental observation is known as Friedel’s law of rational symmetric intercepts.
Bravais and Mallard had begun the theory of twinning. In 1904 Friedel completed it and stated the general law that governs all twins: a lattice, the “twin lattice,” extends through the whole crystalline edifice; it is the crystal lattice itself or one of its superlattices; its prolongation from one of the twinned crystals to another can be exact or approximate. Hence the four possibilities and the classification of twins into four classes. The theory accounted for all known twins but one: the Zinnwald twin in quartz.
Lehmann’s so-called liquid crystals were thoroughly investigated by Friedel and his co-workers Francois Grandjean, Louis Royer, and his son Edmond from 1907 to 1931. Two new stases, the nematic and the smectic, were found to exist between the amorphous and the crystalline. The four stases are separated by discontinuous transformations, which justify the classification. Friedel’s work on the mesomorphous stases is perhaps the most important of all his contributions: its many new observations and interpretations opened up most of the lines of research now pursued in this field, where it remains the basic reference.
Friedel took an immediate, although theoretical, interest in Laue’s discovery of X-ray diffraction by crystals. As early as 1913 he enumerated the eleven centrosymmetries that can be determined by X rays. Other papers deal with the role of the length of the X-ray wave train, the calculation of intensities, and diffraction by solid solutions.
Friedel was responsible for a theory of crystal growth that brings out the similarity of crystal corrosion by a slightly undersaturated solution and crystal growth in a slightly supersaturated one. The two phenomena are symmetrical with respect to the saturation point. The theory thus explains negative crystals. Curved faces are accounted for by convergent and divergent diffusion.
Friedel pointed out that a holoaxial hemihedry may be simulated by a holohedral crystal grown in an optically active medium. He also studied diamond, clarified its holohedry, discussed its inclusions, ascribed its birefringence to strain, and on rapid heating to 1885°C., found a new allotropic form, still unconfirmed but possibly the “white carbon” described by A. El Goresy and G. Donnay.
Friedel’s chief geological contribution was the recognition of the first mylonite in France in 1906.
As a school administrator at Saint-Étienne, Friedel stressed laboratory work and introduced new courses in statistics, foreign languages, economics, and industrial hygiene. At Strasbourg, he planned the scientific training of geological engineers and was one of the founders of the Petroleum Institute. As a teacher he exerted an enormous influence, which is still felt: his admirable textbook Leçons de cristallographie was reprinted in 1964. Its often quoted preface, entitled “A Warning,” is a sort of scientific testament, stressing the importance of meticulous observation and scrupulous acceptance of well-established facts.