MARIGNAC, JEAN CHARLES GALISSARD DE

(b. Geneva, Switzerland, 24 April 1817; d. Geneva, 15 April 1894)

inorganic chemistry, physical chemistry.

Descended from a distinguished Huguenot family, Marignac was the son of Jacob de Marignac, a judge and conseiller d’état. His mother was the sister of the pharmacist and physiologist Augustin Le Royer, whose house and laboratory adjoining the Marignac home was a center of Genevan scientific life. In 1835, after education at the Académie de Genève, Marignac entered the école Polytechique in Paris, where he attended the chemistry lectures of Le Royer’sformer pupil J. B. Dumas. From 1837 to 1839 he studied engineering and mineralogy at the école des Mines. During 1840 Marignac traveled extensively through Europe, and for a short time he studied the derivatives of naphthalene in Liegig’s laboratory at Giessen—his only research on organic chemistry. Through the influence of Dumas, he spent six months during 1841 at the porcelain factory at Sèvres; but, eager for an academic carrer, in the same year he succeeded Benjamin Delaplanche in the chair of chemistry at the Académie de Genève, taking on in addition the chair of mineralogy in 1845. He resigned in 1878, five years after the Academy became the University of Geneva. From 1884 on, chronic heart disease rendered Marignac a stoic but helpless invalid.

Marignac married Marie Dominicé in 1845. They had five children, one of whom, Édouard, died while a student at the école Polytechnique. Marignac worked unassisted in a damp cellar laboratory for most of his life; and this, together with his reticence and modesty, helped to create the erroneous impression that he was a recluse. From 1846 to 1857 he was a joint editor of the Swiss journal Archives des sciences. He commanded great respect from his students and, with the aged Berzelius’ enthusiastic approval, a worldwide renown for his analytical accuracy. Always modern in outlook, he supported the work on mass action of Guldberg and Waage; he switched to two-volume formulas (such as H₂O) in 1858; and he attended the important Karlsruhe conference in 1860. In the French controversy over equivalent weight versus atomic weights in 1877, he gave statesmanlike support for the modern school.¹

Although Marignac completed a large amount of research on mineralogy (showing, for example, that silica should be represented by the formula SiO₂, not SiO₃, because of the isomorphism between fluorstannates and fluorsilicates) and physical chemistry (where he explored the thermal effects of adding variable concentrations of different solutions together, and the alteration of the specific heats of solutions with dilution), only his contributions to inorganic chemistry will be mentioned here. In this field he accurately determined the atomic weights of nearly thirty elements and helped to unravel the tortuous chemistry of niobium and tantalum, the silicates, the tungstates, and the rare earths.

In 1842, inspired by a wave of criticism of Berzeliu’s atomic weights and by the plausibility of Prout’s hypothesis that atomic weights were whole-number multiples of that of hydrogen, Marignac determined the atomic weights of chlorine, potassium, and silver by various methods accurate to ±10^-3, Although his results did not confirm “Pourt’s law” (as he termed it), he suggested in 1843 that the real multiple might possess only half the atomic weight of hydrogen—a suggestion not approved by Berzelius.²

When, in 1860, Stas dismissed Prout’s law as an “illusion,” Marignac cautioned that deviations from the law of definite proportions might sometimes occur—a possibility suggested by an erroneous view of the composition of acids which he then held. More specultively, he suggested that Prout’s law might be an “ideal” law (like Boyle’ law) which was subject to perturbing influences such that the weights of the sub-atomic particles of the primordial matter (from which ordinary chemical atoms were composed) did not add up to exactly the experimentally determined “atomic” weights. This daring speculation was revived in 1915 by W. D. Harkins and E. D. Wilson, and from it the concept of the packing fraction was developed by F. W. Aston in 1920. Marignac was full of praise for Stas’s reply to his challenge in 1865, but unlike Stas he was never able to accept that chance alone was the reason why atomic weights were so close to integers on the O = 16 scale (which he urged chemists to adopt in 1883). Unlike Crookes, Marignac did not speculate concerning the genesis of elements; althought obviously sympathetic toward Crookes’s hypothesis of 1887, he found it wanting for its dubious arguments drawn from rare-earth separations and spectrocopy.³

Marignac’s groundwork with the rare earths (in which he was frequently helped spectroscopically by his physicist colleague J. L. Soret) began in the 1840’s with the separation of the three cerium oxides from cerite. In 1878 he showed, after exacting fractionations based on differing solubilities, that the erbia extracted from gadolinite contained a colorless earth, ytterbia, which he correctly supposed was an oxide of a new metal, ytterbium. His ytterbia was in fact impure, for L. F. Nilson was able to extract scandia from it in 1879; and in 1907 Urbain separated in into (neo)ytterbia and lutecia (now called lutetia). In 1880 Marignac isolated white and yellow oxides from samarskite, which he uncommittdly labeled Yα and Yβ (samaria). In 1886, at Boisbaudran’s request, he named the former gadolinia, and the element “gadolinium.” Marignac is usually regarded as the discoverer of Ytterbium and gadolinium. In general, his seperations were a strategic and indispensable part of chemist,’ success in understanding the elements of the rare-earth series.

NOTES

1. For the debates at the French Academy of Sciences, see Comptes rendus … de l’Académie des sciences, 84 (1877), passim; and Marignac’s comments, in his Oeuvres, II, 649–667.

2. J. J. Berzelius, in the Swedish Academy’s Jahres-Bericht, 2 (1845), 60–62. In 1858 Marignac pointed out that a quarter-unit would preserve Prout’s law. Oeuvres, I, 571.

3. For Crookes’ reply, see Chemical News …, 56 (1887), 39–40.

BIBLIOGRAPHY

I. Original Works. Marignac’s 111 published papers were handsomely repr. as Oeuvres complètes de J. C. Galisard de Marignac, E. Ador, ed., 2 vols. (Geneva, 1902–1903). with portrait and a complete list of Marignac’s atomic weights. From 1846 to 1847 Marignac was joint editor with A. de La Rive of Archives des sciences physiques et naturalles,1–36 (a supp. of the Bibliothèque universelle de Genève). Marignac’s criticism of J. S. Stas is translated in [L. Dobbin and J. Kendall.] Prout’s Hypothesei, Alembic Club Reprints, no, 20 (Ediburgh, 1932), which also contains the relevant portions of Stas’s “answer” of 1865, see “Nouvelles recherches sur les lois des proportions chimiques, sur les poids atomiques et leur rapports mutuels,” in Mémoires de l’ Académie royalede Belgique,35 (1865), 3–311. For Kekeulé’s critiue of Marignac’s criticism, see his “Considérations d’un mémoire de M. Stas su les lois des proportions chimiques,” in Bulletin de l’ Académie royale de Belgique,19 (1865), 411–420. repr. in R. Anschütz, August KeKulé (Berlin, 1929), II, 357–364, For a view of Marginac’s mineralogy by a lifelong friend, see A. L.O. Le Grand des Cloizeaux, Manuel de minéralogie, 2 vols. (Paris, 1862–1874). Two letters from the Berzelius-Marignac correspondence are in H. G. Söderbaum, ed., Jac. Berzelius Bref, III, pt. 7 (Uppsala, 1920), 210–216; note also 253–254.

MSS held by the Bibliothèque Publique et Universitaire de Genève include travel diaries (1839, 1840), analytical notebooks (1844 on), Swiss correspondence, and lecture notes of Marignac’s students.

II. Secondary Literature. The basic life of Marignac is by Ador in the Oeuvres, I, i–lv, repr. from the Archives des sciences,32 (1894), 183–215, and partly repr. with portrait and bibliography in Bulletin de la Société chimique de Paris, 17 (1894), 233–239 and Berichte der Deutschen chemischen Gesellschaft,27 (1894), 979–1021. Other useful notices are P. T. Cleve, “Marignac Memorial Lecture,” in Journal of the Chemical Society,67 (1895), 468–489, with portrait and bibliography, repr. in Memorial Lectures Delivered Before the Chemical Society, 1893–1900 (London, 1901); and “De Marigance,” in Société des Amis de l’école, L’école polytechnique (Paris, 1932), pp. 194–196.

Information on Marignac’s atomic weights is in Prout’s Hypothesis (see above); I. Freund, The Study of Chemical Composition (Cambridge, 1904; repr. New York, 1968), pp. 599–603; and W. V. Farrar, “Nineteenth-Century Speculations on the Complexity of the Chemical Elements,” in British Journal for the History of Science,2 (1965), 307–308. For Marignac’s contribution to rare-earth chemistry, see the obituary by Cleve (above); O. I. Deineka, “Issledovania Mariniaka po khimii redkozemelnykh elementov” (“The Research of Marignac in the Chemistry of the Rare-Earth Elements”), in Trudy Instituta istorii estestvoznaniya i tekhniki,39 (1962), 87–94; and M. E. Weeks, Discovery of the Elements, 7th ed. (Easton, Pa., 1968), ch. 16, passim.

W. H. Brock