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tetroxide, Cb2O4 is obtained as a black powder when the pentoxide is heated to a high temperature in a current of hydrogen. It is unattacked by acids. Columbium pentoxide (columbic acid), Cb2O5, is obtained from columbite, after the removal of tantalum (see above). The mother liquors are concentrated, and the double salt of composition 2KF·CbOF3·H2O, which separates, is decomposed by sulphuric acid, or by continued boiling with water (C. Marignac; see also G. Krüss and L. F. Nilson, Ber. 1887, 20, p. 1676). It is a white amorphous infusible powder, which when strongly heated in sulphuretted hydrogen, yields an oxysulphide. Several hydrated forms are known, yielding salts known as columbates. A percolumbic acid, HCbO4·nH2O, has been prepared by P. Melikoff and L. Pissarjewsky (Zeit. f. anorg. Chem. 1899, 20, p. 341), as a yellow amorphous powder by the action of dilute sulphuric acid on the potassium salt, which is formed when columbic acid is fused in a silver crucible with eight times its weight of caustic potash (loc. cit.). Salts of the acid H3CbO8 have been described by C. W. Balke and E. F. Smith (Jour. Amer. Chem. Soc. 1908, 30, p. 1637).

Columbium trichloride, CbCl3, is obtained in needles or crystalline crusts, when the vapour of the pentachloride is slowly passed through a red-hot tube. When heated in a current of carbon dioxide it forms the oxychloride CbOCl3, and carbon monoxide. Columbium pentachloride, CbCl5, is obtained in yellow needles when a mixture of the pentoxide and sugar charcoal is heated in a current of air-free chlorine. It melts at 194° C. (H. Deville) and boils at 240.5° C. It is decomposed by water, and dissolves in hydrochloric acid. Columbium oxychloride, CbOCl3, is formed when carbon tetrachloride, and columbic acid are heated together at 440° C.: 3CCl4 + Cb2O5 = 2CbOCl3 + 3COCl2, and also by distilling the pentachloride, in a current of carbon dioxide, over ignited columbic acid. It forms a white silky mass which volatilizes at about 400° C. It deliquesces in moist air, and is decomposed violently by water. Columbium pentafluoride, CbF5, is obtained when the pentoxide is dissolved in hydrofluoric acid. It is only known in solution; evaporation of the solution yields the pentoxide. The oxyfluoride, CbOF3, results when a mixture of the pentoxide and fluorspar is heated in a current of hydrochloric acid. It forms many double salts with other metallic fluorides.

Columbium oxysulphide, CbOS3, is obtained as a dark bronze coloured powder when the pentoxide is heated to a white heat in a current of carbon bisulphide vapour; or by gently heating the oxychloride in a current of sulphuretted hydrogen. It burns when heated in air, forming the pentoxide and sulphur dioxide.

Columbium nitride, Cb3N5 (?), is formed when dry ammonia gas is passed into an ethereal solution of the chloride. A heavy white precipitate, consisting of ammonium chloride and columbium nitride, is thrown down, and the ammonium chloride is removed by washing it out with hot water, when the columbium nitride remains as an amorphous residue (Hall and Smith, loc. cit.).

Potassium fluoxy percolumbate, K2CbO2F5·H2O, is prepared by dissolving potassium columbium oxyfluoride in a 3% solution of hydrogen peroxide. The solution turns yellow in colour, and, when saturated, deposits a pasty mass of crystals. The salt separates from solutions containing hydrofluoric acid in large plates, which are greenish yellow in colour.

The atomic weight was determined by C. Marignac (Ann. chim. et phys. 1866 (4), 8, p. 16) to be 94 from the analysis of potassium columbium oxyfluoride, and the same value has been obtained by T. W. Richards (Journ. Amer. Chem. Soc. 1898, 20, p. 543).

COLUMBUS, CHRISTOPHER [in Spanish Cristobal Colón] (c. 1446, or perhaps rather 1451,–1506) was the eldest son of Domenico Colombo and Suzanna Fontanarossa, and was born at Genoa either about 1446 or in 1451, the exact date being uncertain. His father was a wool-comber, of some small means, who lived till 1498. According to the life of Columbus by his son Ferdinand (a statement supported by Las Casas), young Christopher was sent to the university of Pavia, where he devoted himself to astronomy, geometry and cosmography. Yet, according to the admiral’s own statement, he became a sailor at fourteen. Evidently this statement, however, cannot mean the abandonment of all other employment, for in 1470, 1472, and 1473 we find him engaged in trade at Genoa, following the family business of weaving, and (in 1473) residing at the neighbouring Savona. In 1474–1475 he appears to have visited Chios, where he may have resided some time, returning to Genoa perhaps early in 1476. Thence he seems to have again set out on a voyage in the summer of 1476, perhaps bound for England; on the 13th of August 1476, the four Genoese vessels he accompanied were attacked off Cape St Vincent by a privateer, one Guillaume de Casenove, surnamed Coullon or Colombo (“Columbus”); two of the four ships escaped, with Christopher, to Lisbon. In December 1476, the latter resumed their voyage to England, probably carrying with them Columbus, who, after a short stay in England, claims to have made a voyage in the northern seas, and even to have visited Iceland about February 1477. This last pretension is gravely disputed, but it is perhaps not to be rejected, and we may also trace the Genoese about this time at Bristol, at Galway, and probably among the islands west and north of Scotland. Soon after this he returned to Portugal, where (probably in 1478) he married a lady of some rank, Felipa Moñiz de Perestrello, daughter of Bartholomew Perestrello, a captain in the service of Prince Henry the Navigator, and one of the early colonists and first governor of Porto Santo. Felipa was also a cousin of the archbishop of Lisbon at this time (1478).

About 1479 Columbus visited Porto Santo, here as in Portugal probably employing his time in making maps and charts for a livelihood, while he pored over the logs and papers of his deceased father-in-law, and talked with old seamen of their voyages, and of the mystery of the western seas. About this time, too, if not earlier, he seems to have arrived at the conclusion that much of the world remained undiscovered, and step by step conceived that design of reaching Asia by sailing west which was to result Idea of western passage to Asia. in the discovery of America. In 1474 he is said to have corresponded with Paolo Toscanelli, the Florentine physician and cosmographer, and to have received from him valuable suggestions, both by map and letter, for such a Western enterprise. (The whole of this incident has been disputed by some recent critics.) He had perhaps already begun his studies in a number of works, especially the Book of Marco Polo and the Imago Mundi of Pierre d’Ailly, by which his cosmographical and geographical conceptions were largely moulded. His views, as finally developed and presented to the courts of Portugal and Spain, were supported by three principal lines of argument, derived from natural reasons, from the theories of geographers, and from the reports and traditions of mariners. He believed the world to be a sphere; he underestimated its size; he overestimated the size of the Asiatic continent. And the farther that continent extended towards the east, the nearer it came towards Spain. Nor were these theories the only supports of his idea. Martin Vicente, a Portuguese pilot, was said to have found, 400 leagues to the westward of Cape St Vincent, and after a westerly gale of many days’ duration, a piece of strange wood, wrought, but not with iron; Pedro Correa, Columbus’s own brother-in-law, was said to have seen another such waif at Porto Santo, with great canes capable of holding four quarts of wine between joint and joint, and to have heard of two men being washed up at Flores “very broad-faced, and differing in aspect from Christians.” West of Europe, now and then, men fancied there hove in sight the mysterious islands of St Brandan, of Brazil, of Antillia or of the Seven Cities. In his northern journey, too, some vague and formless traditions may have reached the explorer’s ear of the voyages of Leif Ericson and Thorfinn Karlsefne, and of the coasts of Markland and Vinland. All were hints and rumours to bid the bold mariner sail towards the setting sun, and this he at length determined to do.

The concurrence of some state or sovereign, however, was necessary for the success of this design. Columbus, on the accession of John II. of Portugal, seems to have entered the service of this country, to have accompanied Quest of a patron.Diego d’Azambuja to the Gold Coast, and to have taken part in the construction of the famous fort of St George at El Mina (1481–1482). On his return from this expedition, he submitted to King John the scheme he had now matured for reaching Asia by a western route across the ocean. The king was deeply interested in the rival scheme (of an eastern or south-eastern route round Africa to India) which had so long held the field, which had been initiated by the Genoese in 1291, and which had been revived, for Portugal, by Prince Henry the Navigator; but he listened to the Genoese, and referred him to a committee of council for geographical affairs. The council’s report was adverse; but the king, who was yet inclined to favour the theory of Columbus, assented to the suggestion of the bishop of Ceuta that the plan should be carried out in secret and without its author’s knowledge. A caravel was despatched; but it returned after a brief absence, the sailors