COATI, or Coati-Mundi, the native name of the members of the genus Nasua, of the mammalian family Procyonidae. They are easily recognized by their long body and tail, and elongated, upturned snout; from which last feature the Germans call them Rüsselbären or “snouted bears.” In the white-nosed coati, a native of Mexico and Central America, the general hue is brown, but the snout and upper lip are white, and the tail is often banded. In the red coati, ranging from Surinam to Paraguay, the tail is marked with from seven to nine broad fulvous or rufous rings, alternating with black ones, and tipped with black. Coatis are gregarious and arboreal in habit, and feed on birds, eggs, lizards and insects. They are common pets of the Spaniards in South America. (See [Carnivora].)
COB, a word of unknown origin with a variety of meanings, which the New English Dictionary considers may be traced to the notions of something stout, big, round, head or top. In “cobble,” e.g. in the sense of a round stone used in paving, the same word may be traced. The principal uses of “cob” are for a stocky strongly built horse, from 13 to 14 hands high, a small round loaf, a round lump of coal, in which sense “cobble” is also used, the fruiting spike of the maize plant, and a large nut of the hazel type, more commonly known as the cob-nut.
“Cobbler,” a patcher or mender of boots and shoes, is probably from a different root. It has nothing to do with an O. Fr. coubler, Mod. coupler, to fasten together. In “cobweb,” the web of the spider, the “cob” represents the older cop, coppe, spider, cf. Dutch spinnekop.
COBALT (symbol Co, atomic weight 59), one of the metallic chemical elements. The term “cobalt” is met with in the writings of Paracelsus, Agricola and Basil Valentine, being used to denote substances which, although resembling metallic ores, gave no metal on smelting. At a later date it was the name given to the mineral used for the production of a blue colour in glass. In 1735 G. Brandt prepared an impure cobalt metal, which was magnetic and very infusible. Cobalt is usually found associated with nickel, and frequently with arsenic, the chief ores being speiss-cobalt, (Co,Ni,Fe)As2, cobaltite (q.v.), wad, cobalt bloom, linnaeite, Co3S4, and skutterudite, CoAs3. Its presence has also been detected in the sun and in meteoric iron. For the technical preparation of cobalt, and its separation from nickel, see [Nickel]. The metal is chiefly used, as the oxide, for colouring glass and porcelain.
Metallic cobalt may be obtained by reduction of the oxide or chloride in a current of hydrogen at a red heat, or by heating the oxalate, under a layer of powdered glass. As prepared by the reduction of the oxide it is a grey powder. In the massive state it has a colour resembling polished iron, and is malleable and very tough. It has a specific gravity of 8.8, and it melts at 1530° C. (H. Copaux). Its mean specific heat between 9° and 97° C. is 0.10674 (H. Kopp). It is permanent in dry air, but in the finely divided state it rapidly combines with oxygen, the compact metal requiring a strong heating to bring about this combination. It decomposes steam at a red heat, and slowly dissolves in dilute hydrochloric and sulphuric acids, but more readily in nitric acid. Cobalt burns in nitric oxide at 150° C. giving the monoxide. It may be obtained in the pure state, according to C. Winkler (Zeit. für anorg. Chem., 1895, 8, p. 1), by electrolysing the pure sulphate in the presence of ammonium sulphate and ammonia, using platinum electrodes, any occluded oxygen in the deposited metal being removed by heating in a current of hydrogen.
Three characteristic oxides of cobalt are known, the monoxide, CoO, the sesquioxide, Co2O3, and tricobalt tetroxide, Co3O4; besides these there are probably oxides of composition CoO2, Co8O9, Co6O7 and Co4O5. Cobalt monoxide, CoO, is prepared by heating the hydroxide or carbonate in a current of air, or by heating the oxide Co3O4 in a current of carbon dioxide. It is a brown coloured powder which is stable in air, but gives a higher oxide when heated. On heating in hydrogen, ammonia or carbon monoxide, or with carbon or sodium, it is reduced to the metallic state. It is readily soluble in warm dilute mineral acids forming cobaltous salts. Cobaltous hydroxide, Co(OH)2, is formed when a cobaltous salt is precipitated by caustic potash in the absence of air. A blue basic salt is precipitated first, which, on boiling, rapidly changes to the rose-coloured hydroxide. It dissolves in acids forming cobaltous salts, and on exposure to air it rapidly absorbs oxygen, turning brown in colour. A. de Schulten (Comptes Rendus, 1889, 109, p. 266) has obtained it in a crystalline form; the crystals have a specific gravity of 3.597, and are easily soluble in warm ammonium chloride solution. Cobalt sesquioxide, Co2O3, remains as a dark-brown powder when cobalt nitrate is gently heated. Heated at 190-300° in a current of hydrogen it gives the oxide Co3O4, while at higher temperatures the monoxide is formed, and ultimately cobalt is obtained. Cobaltic hydroxide, Co(OH)3, is formed when a cobalt salt is precipitated by an alkaline hypochlorite, or on passing chlorine through water containing suspended cobaltous hydroxide or carbonate. It is a brown-black powder soluble in hydrochloric acid, chlorine being simultaneously liberated. This hydroxide is soluble in well cooled acids, forming solutions which contain cobaltic salts, one of the most stable of which is the acetate. Cobalt dioxide, CoO2, has not yet been isolated in the pure state; it is probably formed when iodine and caustic soda are added to a solution of a cobaltous salt. By suspending cobaltous hydroxide in water and adding hydrogen peroxide, a strongly acid liquid is obtained (after filtering) which probably contains cobaltous acid, H2CoO3. The barium and magnesium salts of this acid are formed when baryta and magnesia are fused with cobalt sesquioxide. Tricobalt tetroxide, Co3O4, is produced when the other oxides, or the nitrate, are heated in air. By heating a mixture of cobalt oxalate and sal-ammoniac in air, it is obtained in the form of minute hard octahedra, which are not magnetic, and are only soluble in concentrated sulphuric acid.
The cobaltous salts are formed when the metal, cobaltous oxide, hydroxide or carbonate, are dissolved in acids, or, in the case of the insoluble salts, by precipitation. The insoluble salts are rose-red or violet in colour. The soluble salts are, when in the hydrated condition, also red, but in the anhydrous condition are blue. They are precipitated from their alkaline solutions as cobalt sulphide by sulphuretted hydrogen, but this precipitation is prevented by the presence of citric and tartaric acids; similarly the presence of ammonium salts hinders their precipitation by caustic alkalis. Alkaline carbonates give precipitates of basic carbonates, the formation of which is also retarded by the presence of ammonium salts. For the action of ammonia on the cobaltous salts in the presence of air see Cobaltammines (below). On the addition of potassium cyanide they give a brown precipitate of cobalt cyanide, Co(CN)2, which dissolves in excess of potassium cyanide to a green solution.
Cobalt chloride, CoCl2, in the anhydrous state, is formed by burning the metal in chlorine or by heating the sulphide in a current of the same gas. It is blue in colour and sublimes readily. It dissolves easily in water, forming the hydrated chloride, CoCl2·6H2O, which may also be prepared by dissolving the hydroxide or carbonate in hydrochloric acid. The hydrated salt forms rose-red prisms, readily soluble in water to a red solution, and in alcohol to a blue solution. Other hydrated forms of the chloride, of composition CoCl2·2H2O and CoCl2·4H2O have been described (P. Sabatier, Bull. Soc. Chim. 51, p. 88; Bersch, Jahresb. d. Chemie, 1867, p. 291). Double chlorides of composition CoCl2·NH4Cl·6H2O; CoCl2·SnCl4·6H2O and CoCl2·2CdCl2·12H2O are also known. By the addition of excess of ammonia to a cobalt chloride solution in absence of air, a greenish-blue precipitate is obtained which, on heating, dissolves in the solution, giving a rose-red liquid. This solution, on standing, deposits octahedra of the composition CoCl2·6NH3. These crystals when heated to 120° C. lose ammonia and are converted into the compound CoCl2·2NH3 (E. Frémy). The bromide, CoBr2, resembles the chloride, and may be prepared by similar methods. The hydrated salt readily loses water on heating, forming at 100° C. the hydrate CoBr2·2H2O, and at 130° C. passing into the anhydrous form. The iodide, CoI2, is produced by heating cobalt and iodine together, and forms a greyish-green mass which dissolves readily in water forming a red solution. On evaporating this solution the hydrated salt CoI2·6H2O is obtained in hexagonal prisms. It behaves in an analogous manner to CoBr2·6H2O on heating.