IRON. 



149 



In Scotland the use of the hot blast has given a 

 great impulse to the manufacture. This has been 

 aided by the introduction of a rich bed of iron stone, 

 called black band, which could not be wrought well 

 with the cold air. The number of furnaces in Scot- 

 land are : 



Pure Iron. In specific gravity is 7.7, but it may 

 be made 7.8 by hammering. The specific gravity of 

 cast iron is 7.281; that of steel, 7.795. Under the 

 the article Cohesion, the tenacity of iron, compared 

 with that of some of the other metals, is given. 

 In malleability, it is much inferior to gold, silver 

 and copper ; but in ductility, it approaches these 

 metals, iron wires of one hundred and fiftieth of an 

 inch being frequently drawn. It melts in the 

 extreme heat of chemical furnaces, which equals 

 158 Wedgewood. We have noticed, under the 

 head of Native Iron, the crystalline texture of this 

 metal, as found in nature. A mass of bar iron, 

 which has undergone all the operations of puddling 

 and rolling, after being left in liquid muriatic acid 

 till saturation, presents the appearance of a bundle 

 of fasces, whose fibres run parallel through its whole 

 length. At the two ends of the mass, the points 

 appear perfectly detached from each other, and the 

 fibres are so distinct as to seem to the eye to be but 

 loosely compacted. Iron by friction acquires a 

 peculiar smell, and it possesses the colour distinctive- 

 ly called iron-gray. Bars of it, kept in a vertical 

 position, or at an angle of 70 to the horizon, become 

 magnetic spontaneously. They may also be mag- 

 netized by percussion, or an electric shock, either 

 from a common machine or a thunder eloud. The 

 magnetic effect is rendered most powerful, in a bar 

 of iron, by allowing galvanic electricity to circulate 

 in circles round it, after being bent into the shape of 

 i horse shoe. A bar, weighing twenty-one pounds, 

 has, in this manner, been made to support a weight of 

 750 pounds ; and the galvanic battery employed 

 consisted merely of two concentric copper cylinders, 

 with a third, of zinc, between them, which were 

 immersed in half a pint of dilute acid. The magne- 

 tism of soft iron, however, is not permanent, like 

 that of steel. Iron burns with the greatest facility, 

 as may be seen in the shops of the smiths, where, on 

 withdrawing a bar of iron from the fire, at a white 



tieat, it emits brilliant sparks in every direction. 

 It is also visible by projecting iron filings upon a 

 lighted candle or a common fire. Its combustion in 

 these cases is the result of its combination with the 

 oxygen of the atmosphere. When it is heated and 

 introduced into a vessel of pure oxygen gas, its 

 combustion is vastly more rapid, and the scintillation 

 which it occasions is extremely brilliant. There 

 are only two non-metallic combustibles, hydrogen 

 and nitrogen, which have not hitherto been combined 

 with iron. Carbon, boron, phosphorus, sulphur and 

 selenium, form with it compounds more or less 

 intimate. The same thing holds of most of the 

 metals. When cold, it is without action on pure 

 water, but decomposes it rapidly when heated to the 

 degree of incandescence. The rusting of iron in a 

 damp atmosphere has been ascribed to the joint 

 agency of carbonic acid and water. 



Compounds of Iron. Iron unites with oxygen to 

 form three, and, possibly, four oxides. The first 

 oxide is obtained either by digesting an excess of 

 iron filings in water, by the combustion of iron wire 

 in oxygen, or by adding pure ammonia to a solution 

 of green copperas, and drying the precipitate out of 

 contact of air. It is of a black colour, becoming 

 white by its union with water in the hydrate, attract- 

 able by the magnet, but more feebly than iron. Its 

 composition is, 



Iron, 100.0 77.82 3.5 



Ogygen, 28.5.... 22.18 1.0 



The second or deutoxide of iron is formed by expos- 

 ing a coil of fine iron wire, in an ignited porcelain 

 tube, to a current of steam, as long as any hydrogen 

 comes over. Its composition is, 



Iron, 100 72.72 



Oxygen, 37.5 27.28 



The fourth oxide is obtained by igniting the nitrate, 

 or carbonate of iron, by calcining iron in open 

 vessels, or simply by treating the metal with strong 

 nitric acid, then washing and drying the residuum. 

 Colcothar of vitriol, or thoroughly calcined copperas 

 may be considered as peroxide of iron. This oxide 

 exists abundantly in nature, as may lie seen by 

 referring to the preceding account of the Ores of 

 Iron. It is a compound of iron, 100, and oxygen, 

 43. The third oxide has not been satisfactorily 

 established. If the experiments upon its nature are 

 correct, its relation to the others may be perceived 

 in the following statement of M. Berthier, in which 

 the quantities of oxygen combined with the same 

 quantity of metal, in the four oxides, are to each 

 other as the numbers 6, 7, 8, 9. There are two 

 chlorides of iron; the first consisting of iron, 46.57 

 and chlorine 53.43; the second of iron 35.1, and 

 chloride 64.9. The proto-chloride is a fixed, the 

 deuto-chioride, a volatile substance. Iodine forms 

 with iron a compound of a light green colour 

 soluble in water. There are two sulphurets of iron. 

 The proto-sulphuret is formed by heating equal 

 weights of iron filings and sulphur in a crucible or 

 iron vessel, to incandescence. It is of a dark gray 

 colour, brittle, feebly magnetic. Its composition is 

 iron 28, sulphur 16. It abounds in nature. (See 

 Magnetic Iron Pyrites, among the Ores of Iron.) 

 The artificial sulphuret varies in composition from 

 the excess of one or the other of its ingredients. It 

 is employed in eudiometry, and is used for the pro- 

 duction of sulphureted hydrogen gas, which it 

 evolves copiously on the addition of diluted muriatic 

 or sulphuric acid. The persulphuret of iron is the 

 common iron pyrites found so abundantly in nature. 

 It is composed of iron 28, and sulphur 32. There is 

 also a phosphuret, formed by calcining four parts of 

 phosphate of iron, and one of lampblack, in a covered 

 crucible. It does not act on the magnetic needle ; 



