SéNARMONT, HENRI HUREAU DE

(b. Broué. Eure-et-Lorie, France, 6 September 1808; d Paris France, 30 June 1862)

Crystallography, moneralogy

At Sénarmont’s request, no obituaries appeared after his death; thus little is known of his private life. He was the son of Amèdeè Hureau Sènarmont, a landowner in Badonville in the commune of Brouè, and Amèlie Rey. After attending the Collège Rollin and the Collège Charlemangne in Paris, he entered the École Polytechnique in 1826. Three years later he joined the state mining administration as eleve-ingenieur. In this capacity he visited (1831) the arsenal in Toulouse and was assigned to the steel mills in Rive-de-Gier and LeCreusot. In 1833 he worked temporarily with the engineer Conte, who was carrying out special assignments in the Autun basin. In 1835 he became a mining engineer, second class.

Sénarmont’s work brought him to Nantes and Angers in 1835–1836. In the summer of the latter year he was assigned to prepare geological maps of Aube and Seine-et-Oise. (Seine-et-Marne was added in 1837, and the map of Aube was canceled in 1839.) In 1843 he published Sur la geologie des departements de Seine-et-Oise et Seine-et-Marne, which appeared in two sections the following year.

From 1840 to 1847 Sénarmont was engaged in inspecting steam engines in the Seine department. He was promoted to mining engineer, first class, in 1841 and then, in 1848, to assistant chief engineer. In 1847 he was made an examiner at the École Polytechnique; but in the same year he was transferred to the École des Mines, where he received the chair of mineralogy. In 1849 Sénarmont joined the editorial staff of the Annales des mines. Later he was named dean of students, librarian, and secretary of the council at the École des Mines. In 1852, following the death of Beudant, Sénarmont became a member of the mineralogy section as vice-president in 1858 and as president in 1859. In 1854 he became an editor of the Annales de chimie et de Physique and held this post until his death. He also received the chair of physics at the École Polytechnique (1856–1862).

Sénarmont’s enthusiasm for crystallography was first awakened by Fresnel. His importance is based on his demonstration of the directional dependency of the physical properties of crystals and on his experiments on the synthesis of minerals under conditions corresponding to those in nature. In his first paper, “Memoire sur les modifications que lareflexion spécularire á la surface des corps metalliques imprime á un rayon de lumiere polarisee” (1840), Sénarmont introduced, for the purpose of measuring phase differences, a thin layer of mica known as the 1/4 λ plate. In “Memoire sur la reflexion et la double refraction de la lumiére parles cristaux doués de l’"opacité metallique” (1847), he discussed perpendicular incidence on calcite and stated (1) that a rotation of the plane of polarization can be observed and (2) that an analogous rotation of the plane of polarization occurs for reflected light on stibnite (antimony sulfide) and is evidence of double refraction. The difficulty of the problems that Sénarmont investigated is evident when one considers that it was only in 1887 that Drude attempted to determine quantitatively the optical properties of stibnite, and not until 1931 that problems of quantitative ore microscopy were clarified by Max Berek.

In 1850 Sénarmont described his polariscope (Figure 1), a plate composed of four quartz prisms with its upper and lower faces normal to the optic axis (D and D’ are optically rotatory clockwise and G and G’ counterclockwise):

If this parallel-sided plate is set at right angles to a beam of polarized, parallel light–that is to say, in such a way that the light is traveling along the optic axis–the plate will be seen to be covered with straight fringes parallel to the refracting edges of the prisms. If the principal section of Academie des Sciences: he served as vice-president the analyzer is the same as the initial plane of polarization, the dark central fringe will be situated in the middle of the plate. Where the thickness of each of the crossed prisms is the same; hence it will form a straight line along the front back havlves of the plate,¹

Sénarmont made important contributions to isomorphism in “Recherches sur les Propriétés optiques biréfringentes des corps isomorphes” (1851). Besides an exact description of his procedures, he furnished a considerable amount of crystallographic data and described many isomorphic compounds. To determine the character of the axes of optical elasticity, he utilized quartz plates and wedges: “The thickness is always that which is required to produce colors by compensation if the slightly prismatic laminae recommended by M. Biot are employed; and the axis of the plate parallel to the optical axis of the quartz will always be the quartz will always be the one of greatest optical elasticity.”²

In his “Recherches” Sénarmont also provided a method for measuring the binormal angle (optic axial angle)

in convergently polarized light (Figure 2). If and , it follows that

Here, i and I are the corresponding angles of emergence, θ and θ the apparent half-angles of the optic axes after this emergence, and/the index of refraction. Thus Sénarmont was able to determine the binormal angle of K₂SO₄ without knowing the index of refraction. In this work he also described the dispersion of the optic axes and the shift of the plane of these axes toward red in crystalline solid solutions of potassium Rochelle salt and ammonium Rochelle salt.

In “Recherches sur la double réfraction” (1856), Sénarmont provided a thorough account of all of the phenomena related to parallel and convergent polarized light beams. He also observed carefully the boundary cones of rays in total reflection. In “Sur la réflexion totale de la lumiére extérieurement à la surface des cristaux biréfringents” (1856), he developed the formulas for conic sections in optically uniaxial crystals and in certain optically biaxial crystals. Virtually the only fluid refractive medium available to him was carbon disulfide. In “Note sur quelques formules propres à la détermination des trois indices principaux dans les cristaux biréfringents” (1857), he applied the method of minimal diffraction to prisms of doubly refractive crystals in order to determine the principal indexes of refraction.

In “Mémoires sur la conductibilité des substances cristallisées pour la chaleur” (1847), Sénarmont demonstrated that thermal conductivity is dependent on crystal symmetry. He bored through the middle of thin crystal plates, waxed them, and through the hole placed a silver tube, which he heated. The swelling of the wax indicated an isothermal corresponding to the melting temperature of the wax. On all the slices of isometric crystals and on all the basal slices of tetragonal and hexagonal crystals, the isotherms were circular; in all other cases they were elliptical. From these patterns of swelling in the wax he recognized the optically positive nature of quartz. In 1848 he showed that, when subjected to unilateral pressure, melting isotropic bodies (like glass) yield isotherms that resemble those that are characteristic of anisotropic materials.

Analogously, Sénarmont established the directional dependence of surface conductivity in crystals in “Mémoire sur la conductibilité superficielle des corps cristallisées pour l’électicité de tension” (1850). He discovered this dependence by wrapping a crystal in tinfoil (which had been grounded) and by placing a metal point on the crystal surface at a point where a circular piece of the tinfoil had been cut out; the point was then connected to the positive conductor of an electrostatic machine, and the whole apparatus was placed under the glass bell of an air pump. At reduced pressure he was able to observe, in the dark, circular or elliptical figures of light, depending on the nature of the crystal. He stated that: “The continuous and silent flux of the electricity of the rarefied air does not, it is true, leave permanent traces; but it does manifest itself in the darkness by a faint light that persists throughout the whole experiment and that makes all its details visible...."³

In “Expériences sur la production artificielle de polychromisme dans les substances cristallisées” (1851), Sénarmont was the first to describe the production of artificial pleochroism in strontium nitrate pentahydrate, which had been prepared by saturating the substance with ammoniacal logwood extract and other organic dyestuffs. He also reported on less successful experiments involving rock candy (sugar), Rochelle salt, potassium nitrate, and sodium nitrate.

The syntheses that Sénarmont carried out in the years 1849–1851 are recounted in “Expériences sur la formation des minéraux par la voie humide dans les gîtes métallifères concrétionnées” (1851) and are an essential contribution to the understanding of mineral formation. Since CO₂, H₂S, alkali salts, sulfides, and carbonates predominate in thermal springs, he assumed that the formation of ore veins from these components would necessarily occur at elevated temperatures and pressures. Thus he placed those components that he wished to have interact in sealed glass tubes, which were inserted into a sealed pipe filled with water. The apparatus was then embedded in coal dust and heated in the gas ovens of the steel mills at Ivry-sur-Seine. Through either double decomposition of a soluble salt with Na₂CO₃, or precipitation of a coluble salt using alkali carbonate in a supersaturated CO₂ solution, Sénarmont produced magnesite, siderite, rhodochrosite, cobalt carbonate, nickel carbonate, smithsonite, and malachite, as well as barite, fluorite, and quartz in crystalline form.

Sénarmont also synthesized pure silver, copper, arsenic, and hematite. From metallic salts and alkali sulfides he obtained mostly amorphous sulfides—including marcasite, pyrite, manganese sulfide, hauerite, NiS, CO₃S₄, Sphalerite, galena, and chalcopyrite; and he obtained realgar, orpiment, stibnite, bismuthinite, arsenopyrite, proustite, and pyrargyrite in crystalline form. He was similarly successful in crystallizing PbS and ZnS in a supersaturated H₂S solution and in obtaining pyrite and chalcopyrite in the form of a granulated powder with metallic luster. If he wished to avoid an immediate reaction, he inserted into the glass tube a thin ampul containing a salt and a gas bubble. When heat was applied the gas bubble burst the ampul. Altogether Sénarmont succeeded in synthesizing twenty-nine vein minerals from the alkali sulfides and carbonates commonly found in thermal springs with metallic salts. In these syntheses the temperature rarely exceeded 350° C. He gave an exact crystallographic description of all the compounds he was able to crystallize. In addition, he described the effect of the solutions employed on the glass tubes, the flaking off of pieces of glass from the tubes, and the danger of explosion involved in the use of sealed tubes (bombs).

In 1851 Sénarmont described for the first time both rhombic antimony bloom (valentinite) from Sensa in Algeria and natural isometric antimony oxide from Minina (near Sensa), thus confirming the dimorphism of Sb₂O₃. Dana gave the name senarmontite to the isometric form of Sb₂O₃. Sénarmont also demonstrated that common silicon carbide belongs to the isometric system (1856).

NOTES

1.Annales de chimie et de physique 3rd ser., 28 (1850), 281.

2.Ibid., 33 (1851), 401.

3.Ibid., 28 (1850), 261.

BIBLIOGRAPHY

I. Original Works. For many of Sénarmont’s important papers written between 1840 and 1851, see Annales de chimie et de physique, 2nd and 3rd ser. The Royal Society Catalogue of Scientific Papers, V (1871), 641–643, lists thirty-eight titles by Sénarmont. Poggendorff, curiously, omits most of the papers that appeared in German journals, as well as “Extraits de minéralogie,” which appeared in Annales des mines, 5th ser., 6–19 (1854–1861). Sénarmont’s personal instructions from and reports to the French mining administration are recorded in Annales des mines, 3rd ser. (1833–1841) and 4th ser. (1842–1851).

II. Secondary Literature. See J. L. F. Bertrand, “Eloge de Sénarmont, lu à la Société des amis des sciences, 16 avril 1863,” in Société de secours des amisdes sciences (1863), 27–56; Walter Fischer, Gesteins und Lagersstättenbildung im Wandel der wissenschaftlichen Anachauung (Stuttgart, 1961); E. Hoppe, Geschichte der Physik (Brunswick, 1926); F. von Kobell, Geschichte der Mineralogie 1650–1860 (Munich, 1864); T. Liebisch, Physikalische Kristallographie (Leipzig, 1891); Joseph Michaud, ed., Biographie universelle ancienne et moderne, XXXIX (1969), 56; F. Pockels, Lehrbuch der Kristalloptik (Leipzig—Berlin, 1906): and Nouvelle biographie générale. XLIII (Paris. 1864).

Walter Fischer