Page:Encyclopædia Britannica, Ninth Edition, v. 14.djvu/308

 292 L A N L A O lively. But Mendelejeff on theoretical grounds insisted that the lower oxide must be looked upon as a sesquioxide Ce 2 3, where Ce 2 = 3F or Ce = |F, and the higher (accordingly) as a binoxide, Ce 2 4 or rather Ce0. 2 . And he asserted the same in regard to the reputed monoxides of lanthanum and didymium. These remarks were little heeded even by the specialists until Hillebraud (partly in conjunc tion with Norton) succeeded in obtaining the three metals as such, and in a truly metallic condition, which admitted of an exact deter mination of the specific heats. The specific heats were found to be for Ce 04479, for La 04485, for Di 04563; and these numbers must be multiplied with MendelejelFs atomic weight to produce &quot;atomic heats&quot; (6 6 ; 6 23 ; 6 6), approximating to values obtain ing for other metals of established atomic weight. Hence MendelejeiF was right. Cerous oxide, Ce 2 3, is obtained by heating the oxalate in an atmosphere of hydrogen, as a bluish-grey powder. The higher oxide Oe0 2 is obtained when any certain salt of a volatile acid (e.g., nitric) is ignited in air ; it is a white powder, which when cold has only a slight touch of yellow in it, but at high temperatures assumes a deep orange-red colour. Cerous chloride, CeCl 3, is obtained by heating the metal, or a mixture of either oxide and charcoal, in dry chlorine gas, as a yellowish-white sublimate, uniting with water into in distinct crystals Ce 2 Cl 6 + 5H 2 0. The cerous sulphate, Ce 2 (S0 4 ) 3 , separates out when its solution is heated. It is soluble in 6 parts of cold, and in about 60 of hot water, and forms a difficultly soluble double salt with sulphate of potash. To obtain the eerie sulphate, when the dioxide is treated with cold concentrated sulphuric acid, and the solution formed by addition of water allowed to evaporate, the salt Ce 2 (SO 4 ) 3 (ous) + 2Ce(S0 4 ) 2 (ic) + 25H 2 separates out in red crystals looking like bichromate of potash. The mother-liquor yields yellow crystals of = Ce(S0 4 ) 2 + 4H 2 0. The most characteristic test for cerium salts is that the colourless cerous solutions, on addition of hypochlorite of soda, give a ml precipitate of a eerie hydrate. Didyniium (Di 2 3 ) solutions have an astringent sweetish taste and a rose-red or violet colour. But their most characteristic property is their beautiful absorption-spectrum, which comes out distinctly with as little as half an inch deep of a solution containing rn-irth of a per cent, of the oxide (Gladstone). Lanthanum (La 2 3 ) solutions have a similar taste to those of didymium salts. They are colourless. The chloride when volatilized between the poles of an induction coil yields a highly characteristic rich line-spectrum, by means of which the least traces of the metal can be detected (Bunsen). Of higher oxides of lanthanum or didymium we had hitherto only indications ; but quite lately Dr Brauner (Chcm. News for 1881, December 23), in Roscoe s laboratory, succeeded in preparing a definite pentoxide, Di 2 5, of didvmium, and also a hydrate of it, Di 2 5 .3H 2 0. Sources. Cerite, though the most abundant, is not the only native source of cerium, lanthanum, and didymium. A. Cossa has found traces of the metals in the ashes of numerous plants, and even in the human body. But it is more important to state that there are a number of rare minerals, of which the chief are known by the names of gadolinite, euxenite, samarskite, which, along with more or less of cerite-metals, contain other rarer earth-metals similar to these. Until lately the handbooks of chemistry quoted only three such rarer members of the family under the names of yttrium, erbium, and terbium ; but these reputed individual elements have, during the last few years, been searchingly analysed by Marignac, M. Delafontaine, L. F. Nilson, P. T. Cleve, J. L. Smith, and others, and under their hands resolved themselves into about a dozen separate elements. The rare earth-metals in fact bid fair to multiply like the little planets in astronomy; and, although in chemistry no firmly established fact can justly be called unim portant, the minor rare earths, in the meantime, are of no general interest, even to the general chemist. Sec Wttrtz, DMionnairede Chimie, 1870; Roscoc and Schorlemmcr, Handbook of Chemistry, 1879; Marignae s and Delafontaine s Memoirs in the Archives des Sciences physiques et natureUes, Liebig s Annalen der Cltemie, 1858-04: Pog- Kendorffs Annalen, 1875 ; Journal f. prakt. Chemie, 1858-62 ; Zeitschrift f. C/iemie, 1862. The Jahresbericht der Chemie is the surest guide to all the literature. (W. D.) LAXZI, LTJIGI (1732-1S10), a writer on Etruscan anti quities and on the history of Italian painting, was born in 1732, and educated as a priest. In 1773 lie was appointed keeper of tlie galleries of Florence, from which time his attention seems to have been divided between the study of Italian painting and the study of Etruscan antiquities and language. In the one field his labours are represented by his Storia Pittorica della Italia, the first portion of which, containing the Florentine, Sienese, Roman, and Neapolitan schools, appeared in 1792, the rest in 1796. The work is translated by Eoscoe. In archaeology his great achieve ment was the work entitled Saggiodi lingua Etrusca, 1789, followed by Saggio delle lingue Jtal. Antiche, 180G. In his memoir on the so called Etruscan vases (Dei va.^i anlichi dipinti volgarmente chiamati Etruschi, 1806) Lanzi rightly perceived their Greek origin and characters. What was true of the antiquities would be true also, he argued, of the Etruscan language, and the object of the Saggio di lingua Etrusca was to prove that this language must be related to that of the neighbouring peoples Romans, Umbrians, Oscans, and Greeks. It is admitted that he was wanting in critical method after a certain point, though at the same time much of the impulse he gave to study arose from his general method of inquiry. It is a sign of the recognition he re ceived that he was allied with E. Q. Yisconti in his great but never accomplished plan of illustrating antiquity alto gether from existing literature and monuments. His notices of ancient sculpture and its various styles appeared as an appendix to the Saggio di lingua Etrusca, and arose out of his careful and minute study of the treasures then added to the Florentine collection from the Villa Medici. The abuse he has often met with from modern writers in the Etruscan language led Corssen (Sprache der Etrusker, i. p. vi.) to protest in the name of his real services to philology and archaeology. Among his latest produc tions may be mentioned his edition of Hesiod s Works and Days, with valuable notes, and a translation in terza It had been begun as far back as 1785, but was recast and completed in 1808. The list of his works closes with his Opere Sacre, a series of treatises on spiritual subjects. Lanzi died of apoplexy, March 30, 1810, in the seventy-eighth year of his age. He was buried in the church of the Santa Croce at Florence, by the side of Michelangelo. LAOCOOX, in Greek legend, was a brother of Anchises, and had been a priest of Apollo, but having married against the will of the god he and the two sons of this marriage were attacked by serpents while preparing to sacrifice a bull at the altar of Poseidon, in whose service Laocoon was then acting as priest. An additional motive for his punish ment consisted in his having warned the Trojans against the wooden horse left by the Greeks. But, whatever his crime may have been, the punishment stands out even among the tragedies of Greek legend as marked by its horror particularly so as it comes to us in Virgil (sEneid, ii. 199 sq. ), and as it is represented in the marble group in the Vatican (see Plate V.). In the oldest existing version of the legend that of Arctinus of Miletus, which has so far been preserved in the excerpts of Proclus the calamity is lessened by the fact that only one of the two sons is killed; and this, as has been pointed out (Arch. Zeitung, 1879, p. 167), agrees with the interpretation which Goethe in his Fropylxa had put on the marble group without reference to the literary tradition. He says : &quot; The younger son struggles and is powerless, and is alarmed ; the father struggles ineffectively, indeed his efforts only increase the opposition; the elder son is least of all injured, he feels neither anguish nor pain, but he is horrified at what he sees happening to his father, and he screams while he pushes the coils of the serpent off from his legs. He is thus an observer, witness, and participant in the incident, and the work is then complete.&quot; Again, &quot; the gradation of the incident is this : the father has become powerless among the coils of the serpent ; the younger son has still strength for resistance but is wounded ; the elder has a prospect of escape.&quot; Lessing, on the other hand, maintained the view that the marble group illustrated the version of the legend given by Virgil, with such differences as were necessary from the different limits of representation imposed on the arts of sculpture and of poetry. These limits required a new definition, and this he undertook in his still famous work, Laokoon (see the edition of Hugo Bliimner, Berlin,