Columbium Compounds

Columbium Compounds for Smoke Producing Pyrotechnic Items were proposed by J. DeMent,... 

Niobium, discovered by Hatchett ia 1801, was first named columbium. In 1844, Rosed thought he had found a new element associated with tantalum (see Tantalum AND tantalum compounds). He called the new element niobium, for Niobe, daughter of Tantalus of Greek mythology. In 1949, the Union of Pure and Apphed Chemistry setded on the name niobium, but in the United States this metal is stiU known also as columbium. Sometimes called a rare metal, niobium is actually more abundant in the earth s cmst than lead. 

Hafnium had lain hidden for untold centuries, not because of its rarity but because of its dose similarity to zirconium (16), and when Professor von Hevesy examined some historic museum specimens of zirconium compounds which had been prepared by Julius Thomsen, C. F. Rammelsberg, A. E. Nordenskjold, J.-C. G. de Marignac, and other experts on the chemistry of zirconium, he found that they contained from 1 to 5 per cent of the new element (26, 27). The latter is far more abundant than silver or gold. Since the earlier chemists were unable to prepare zirconium compounds free from hafnium, the discovery of the new element necessitated a revision of the atomic weight of zirconium (24, 28). Some of the minerals were of nepheline syenitic and some of granitic origin (20). Hafnium and zirconium are so closely related chemically and so closely associated in the mineral realm that their separation is even more difficult than that of niobium (columbium) and tantalum (29). The ratio of hafnium to zirconium is not the same in all minerals. 

Tantalum is found in a number of oxide minerals, which almost invariably also contain niobium (columbium). The most important tantalum-bearing minerals are tantalite and columbite. which are variations of the same natural compound (Fe, Mn)(Ta, Nb Og. Much of the tantalum concentrates has been obtained as a byproduct from tin mining in recent years, tin slags, which are a byproduct of the smelting of cassiierite ores, such as those found in the Republic of Congo. Nigeria, Portugal. Malaya, and Thailand have been an important raw material source for tantalum. 

Preparation of Pure Tungsten Trioxlde.—The oxide prepared by any of the above processes is alwaj s impure, the nature of the imj urities depending on the composition of the ore and on the materials employed in the process. If alkali has been used, the presence of sodium, potassium, or calcium tends to give the product a greenish appearance. Iron, manganese, silica, phosphorus, tin, molybdenum, vanadium, and columbium may all be present, and since tungsten is prone to form complex compounds with many of these, the purification of the oxide is not easily accomplished. 

Compounds of Columbium. — In the majority of its compounds columbium is pentavalent, although it is sometimes trivalent and its oxides present some resemblance to the oxides of nitrogen. There is a marked tendency to form oxy-compounds. 

Superconducting materials can be divided into two general categories—brittle and ductile. The brittle superconductors consist of the intermetallic compounds such as columbium-tin (CbaSn) and vanadium-gallium (VsGa). The ductile superconductors consist of most of the elemental metals as well as alloys such as niobium-zirconium. 

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