Doelter (Cisterich Y De La Torre), Cornelio August Severinus

b. Arroyo, Guayama, Puerto Rico, 16 September 1850; d. Kolbnitz, Carinthia, Austria, 8 August 1930)

chemical mineralogy.

Doelter’s father, Carl August (b. Emmendingen, Baden, 1818), emigrated to Puerto Rico and there married Francisca de Cisterich y de la Torre, whose plantations he managed before becoming a partner of Aldecoa and Company. With his mother, Doelter moved to Karlsruhe, Baden, in 1855 and entered its lyceum in 1860. In 1865 his father brought him to Paris, where he attended the Lycée St. Louis, transferring in 1866 to the Lycée Bonaparte; in 1869 he received the bachelier degree and entered the École Centrale des Arts et Manufactures. In the fall of 1870 Doelter enrolled at the University of Freiburg im Breisgau and transferred in the spring of 1871 to Heidelberg. He studied chemistry, physics, mineralogy, and geology, and his most important teachers were Bunsen, J. F. C. Klein, and E. W. Benecke. Following his receipt of the Ph.D. in 1872 he studied under Suess, F. von Hochstetter, and Carl Hauer in Vienna. In 1873 Doelter became a laboratory assistant at the Imperial Geological Survey, and in 1875 he qualified as a lecturer at the University of Vienna. On 1 May 1876 he was appointed assistant professor of mineralogy and petrography at the University of Graz; he was named full professor in 1883. In 1907 Doelter succeeded Tschermak at the University of Vienna, and in 1911 he became imperial Hofrat. He retired in 1921 and continued to live in Vienna, concerning himself chiefly with the preparation of his Handbuch der Mineralchemie.

On 24 August 1876 Doelter married Eleonore Fötterle, who bore him one son and one daughter. The marriage was dissolved in 1915, and on 4 October 1919 he married Maria Theresia Schilgerius. His second wife contributed significantly to the maintenance of his ability to work.

Leitmeier described Doelter thus: “Doelter was a fiery spirit. His ability to make rapid connections was astonishing. Much was not matured, and could scarcely have been so considering the extent of the undertakings. He preferred to direct a staff of assistants, giving only suggestions himself.”¹ Grengg elaborated:

In lectures or in reports, Doelter stood dispassionately above the material, soberly joining one fact to another, illuminating here and there the possibilities of another view, and frequently even leaving to the audience to select for itself what it found most acceptable. Nevertheless, one always had the impression that a man of considerable understanding and wide views was speaking.²

In Graz, Doelter was for a long time editor, and in 1892 also president, of the Naturwissenschaftlicher Verein of Styria; in addition, he was a curator of the Landesmuseum Johanneum. The Akademie der Wissenschaften in Vienna named him a corresponding member on 4 May 1902 and a full member on 2 June 1928. His many students dedicated a Festschrift to him in 1920.

The question of the origin of dolomite had brought Doelter to Vienna in 1872. He worked in the eruptive regions of Hungary and South Tyrol for the Imperial Geological Survey. He considered microscopic and chemical investigation of igneous rock and the exact observation of geological occurrence to be the foundation of all petrology. Doelter conducted a thorough survey of the Pontine Islands (1874), of the volcanism of Monte Ferru on Sardinia, and of the volcanic areas of the Cape Verde Islands, which he visited in 1880–1881. On the trip to the Cape Verde Islands he also went to Portuguese Guinea, where he convincingly explained laterite formation and also made ethnographic studies. He repeatedly explored the Monzoni region and Predazzo in South Tyrol and worked in the crystalline areas of Styria.

Doelter insisted on the confirmation of all suppositions through experiment. He first devoted himself to synthesis and prepared nepheline and pyroxenes (1884), a sulfide and a sulfosalt (1886), micas (1888), and a zeolite (1890). In this work he improved Charles Friedel’s pressure vessels and used liquid and solid carbon dioxide to obtain higher pressure. Experiments on remelting and recrystallization carried out after 1883 had shown that minerals other than the original ones could be separated out from the fused mass. For example, Doelter obtained an augite andesite from a fused mass of eclogite. He likewise investigated the remelting of rocks and the influence of mineralizers on the occurrence of rock-forming minerals. His Allgemeine chemische Mineralogie (Leipzig, 1890) presented the knowledge he had gained of these matters.

In 1890 Doelter studied the absorption of water by dehydrated zeolites and the solubility of silicates in water. At the same time he demonstrated that in electrolysis, fused basalt concentrates iron at the cathode and that, therefore, fused silicates behave like electrolytes and not like alloys. Since the application of the physical-chemical laws developed for aqueous solutions to silicate fusions was hampered by the lack of reliable constants, Doelter began in 1899 to determine the melting points of important minerals and, in 1901, those of mixtures. In 1901 he ascertained the volume increase, of liquid and solidified rock fusions relative to the solid parent rock and found that minerals which are difficult to fuse are also difficult to dissolve and very hard (1902). In 1902 Doelter presented a viscosity series from liquid basalt to viscous granite, recognizing the influence of mineralizers on viscosity and on the lowering of the melting point, as well as their catalytic and chemical activity—e.g., in the formation of mica and of tourmaline. Moreover, he found that magmatic differentiation “is nothing else than the final result of mineral segregation.” ³ For melting-point determinations he constructed the crystallization microscope built by C. Reichert with the heating oven of W. C. Heraeus (described in 1904; improved in 1909). In 1904 he was able to confirm the suspected influence of the inoculation of solution-melts with seed crystals.

With his Physikalisch-chemische Mineralogie (Leipzig, 1905), Doelter showed himself to be, along with J. H. L. Vogt, the most important cofounder of this new discipline, even though he held that the direct transfer of the results of physical chemistry was not always possible, because in silicate fusions a restoration of equilibrium is impeded by the subcooling and by reduced diffusion resulting from viscosity. The chief advantage that he saw in physical chemistry was that it had set the direction that experimental work should follow.

In his Petrogenesis (Brunswick, 1906), a masterful work for its time, Doelter experimentally verified, on the whole, Rosenbusch’s order of crystallization series and related it to solubility, force and velocity of crystal growth, stability, cooling rates, and percentage of mineralizers. Furthermore, he distinguished (1) density differentiation (liquation), which he demonstrated experimentally; (2) crystallization or cooling differentiation by the freezing of basic facies at the boundary of the surfaces of cooling or by the sinking of the earliest segregation products which later form a rock matrix; and (3) isotectic differentiation, in which a definite association of various minerals separates out. In opposition to the views of Vogt, he was able to verify eutectic differentiation only for quartzorthoclase and sporadically for fayalite fusions.

Doelter next turned to research on estimation of the number of nuclei in fused masses, on the force of crystallization, and on the measurement of viscosity (1905); in 1911, with H. Sirk, he obtained the first measurement of the absolute viscosity of molten diopside at 1300°C. From 1907 to 1910 Doelter studied the dissociation constants, electrical conductivities, and polarization of solid and fused silicates. He discovered that in the transition from the moiten to the crystalline state the conductivity changed irregularly, while in the transition to the vitreous state the change was continuous. He held, in opposition to Groth’s conception of lattices of atoms in potassium sulfate, that “one could accept it as more probable that such lattices were made of K′ and SO₄″ ions.”⁴ Even solid, nonconducting sodium chloride could, in his opinion, separate completely or largely into ions, which are fixed in the lattice and which, since they are not mobile, cannot exhibit electrical conductivity.

In addition, Doelter concerned himself with gemmology, particularly with the cause of mineral coloration. In 1896 he began to investigate the influence of Roentgen rays on minerals, and later that of radium rays and of ultraviolet light. He also examined the changes in color resulting from heating minerals in oxidizing, reducing, and inert gases. On the basis of his experience with the coloring agents of synthetic corundums and spinels, Doelter warned against considering analytically or spectroscopically demonstrated trace elements as color pigments, without extensive testing of their behavior when heated in gases and under radiation. Unfortunately these warnings were ignored by many later workers in the field, with the result that contradictory assertions are still published. Doelter even drew upon colloid chemistry in order to clarify these questions—without, however, arriving at any definitive conclusions. Nevertheless his extensive collections of material contain very valuable observations.

Doelter’s some 200 works and those of his students have provided the essential experimental basis for modern petrology.

NOTES

1. H. Leitmeier, in Neue deutsche Biographie, IV (1959), 25.

2. R. Grengg, in Montanistische Rundschau, 22 , no. 19 (1930), 2.

3. Physikalisch-chemische Mineralogie, p. 147.

4. Sitzungsberichte der Akademie der Wissenschaften in Wien, sec. 1, 117 (1908), 333.

BIBLIOGRAPHY

I. Original Works. Doelter’s books include Bestimmung der petrographisch wichtigen Mineralien durch das Mikroskop (Vienna, 1876); Die Vulcane der Capverden und ihre Producte (Graz, 1882); Über die Capuerden nach dem Rio Grande und Futah-Djallon (Leipzig, 1884); Edelsteinkunde (Leipzig, 1893); Das Radium und die Farben (Dresden, 1910); Die Farben der Mineralien, inbesondere der Edelsteine (Brunswick, 1915); and Die Mineralschätze der Balkanländer und Kleinasiens (Stuttgart, 1916). His Handbuck der Mineralchemie was edited by C. Doelter and, from III, pt. 2, with H. Leitmeier; it appeared in 4 vols.: 11 in three pts., III in two pts., and IV in three pts. (Dresden-Leipzig, 1912–1931), About half of the material is by Doelter.

His papers include “Die Vulcangruppe der Pontinischen Inseln,” in Denkschriften der Akademie der Wissenschaften (Vienna), Math.-nat. Kl., 36 , pt. 2 (1876), 141–186; “Der Vulcan Monte Ferru auf Sardinien,” ibid, 38 , pt. 2 (1878), 113–214; “Die Producte des Vulcans Monte Ferru,” ibid., 39 , pt. 2 (1879), 41–95; “Chemische Zusammensetzung und Genesis der Monzonigesteine I–III,” in Tschermaks mineralogische und petrographische Mitteilungen, 21 (1902), 65–76, 97–106, 191–225; “Der Monzoni und seine Gesteine I–II,” in Sitzungsberichte der Akademie der Wissenschaften (Vienna), Math.-nat. Kl., sec. 1, III (1902), 929–986; 112 (1903), 169–236; “Die Silikatschmelzen I–IV.,” ibid., 113 (1904), 177–249, 495–511; 114 (1905), 529–588: 115 (1906), 723–755; “Über die Dissoziation der Silikatschmelzen I–II,” ibid., 116 (1907), 1243–1309; 117 (1908), 299–336; and “Die Elektrizitätsleitung in Krystallen bei höhen Temperaturen,” ibid, 119 (1910), 49–111.

An incomplete list of Doelter’s works, without his contributions to Handbuch der Mineralchemie, is in Poggendorff, III–VI .

II. Secondary Literature. On Doelter or his work see E. Dittler, in Zenlralblatt für Mineraiogie, pt A (1930), 476–477; R. Grengg, in Montanistische Rundschau; 22 , no.19 (1930), 1–2; W. Hammer, in Verhandlungen der Geologischen Bundesanstalt (Vienna, 1930), 213–214; A. Himmelbauer, in Almanach der Akademie der Wissenschaften in Wien, 81 (1931), 314–316; H. Leitmeier, in Neue deutsche Biographie IV (1959), 25–26; and L. J. Spencer, in Mineralogical Magazine, 22 (1930), 390–391.

Various biographical information is to be found in the archives at Graz and Vienna.

Walther Fischer