IRON. 



Siberia, and in the internal parts of South 

 America. This metal, however, in its na- 

 tive state is scarce : most iron is found in 

 the state of oxide, in ochres, bog ores, and 

 other friable earthy substances, of a red, 

 brown, yellow, or black colour. The 

 hematites, or blood stones, are likewise 

 ores with oxide of iron : these are either 

 of a red colour, or blue, yellow, or brown. 

 An iron ore is likewise found, of a blue 

 colour, and powdery appearance. This 

 useful metal is so abundant, that whole 

 mountains are composed of iron stone ; 

 whereas other metals usually run in small 

 veins. Besides these ores of iron, which 

 are either nearly pure, or else mixed with 

 earths, as in spars, jaspers, boles, basaltes, 

 &c. iron is mineralized with sulphur, as 

 in the pyrites, or with arsenic. The coally 

 iron ores contain bitumen. The magnet, 

 or load stone, is an iron ore, the constitu- 

 tion of which has not yet been accurate- 

 ly examined. Iron is also found in com- 

 bination with the sulphuric acid, either 

 dissolved in water, or in the form of sul- 

 phate. 



To analyse the ores of iron in the humid 

 way, they must be reduced to a very sub- 

 tle powder, and repeatedly boiled in mu- 

 riatic acid If the sulphureous ores should 

 prove slow of solution, a small quantity 

 of nitric acid must be added to accelerate 

 the operation. The iron being thus ex- 

 tracted, the insoluble part of the matrix 

 only will remain. Prussiate of potash be- 

 ing added to the decanted solution, will 

 precipitate the iron in the form of Prus- 

 sian blue. This precipitate, when washed 

 and dried, will be equal in weight to six 

 times the quantity of metallic iron it con- 

 tains ; and from this iron four parts in the 

 hundred must be deducted, to allow for 

 the iron which is contained in the prus- 

 siate of potash itself. But as this alkali, 

 and every other preparation containing 

 the prussic acid, does not constantly afford 

 the same quantity of iron, the most exact 

 way, in the use of such preparations, con- 

 sists in previously dissolving a known 

 quantity of iron in sulphuric acid, and 

 .precipitating the whole by the addition of 

 the prussiate of potash. This result will 

 afford a rule for the use of the same 

 alkali in other solutions. For as the 

 weight of the precipitate obtained in the 

 trial experiment is to the quantity of iron 

 which was dissolved and precipitated, so 

 is the weight of the precipitate obtained 

 from any other solution to the quantity of 

 iron sought. 



If the iron be united to any consider- 

 able proportion of zinc or manganese, the 



VOL, Vf. 



Prussian blue must be calcined to red- 

 ness, and treated with strong nitric acid, 

 which will take up the oxide of zinc. 

 The manganese may then be dissolved 

 by nitric acid with the addition of sugar ; 

 and the remaining iron being dissolved by 

 muriatic acid, and precipitated by sub- 

 carbonate of soda, will afford 225 grains 

 of precipitate for every 100 grains of 

 metallic iron. 



To examine the ores of iron in the dry 

 way, the only requisite is fusion, in con- 

 tact with charcoal. For this purpose 

 eight parts of pulverized glass, one of 

 calcined borax, and half a part of char- 

 coal, are to be well mixed together. Two 

 or three parts of this flux being mixed 

 with one of the pounded ore, and placed 

 in a crucible, lined with a mixture of a 

 little clay, and pounded charcoal, with a 

 cover luted on, is to be urged with the 

 strong heat of a smith's forge for half an 

 hour. The weight of the ore, in this ex- 

 periment, should not exceed sixty grains. 

 Other processes for determining the con- 

 tents, or metallic product, of iron ores, 

 are instituted, by performing the same 

 operations in the small, as are intended 

 to be used in the large way. 



In the large iron works, it is usual to 

 roast or calcine the ores of iron, pre- 

 viously to their fusion ; as well for the pur- 

 pose of expelling sulphureous or arseni- 

 cal parts, as to render them more easily 

 broken into fragments of a convenient size 

 for melting. The mineral is melted or 

 run down in large furnaces, from sixteen 

 to thirty feet high ; and variously shaped, 

 either conical or elliptical, according to 

 the opinion of the iron-master. Near the 

 bottom of the furnace is an aperture for 

 the insertion of the pipe of large bellows, 

 worked by water or steam, or of other 

 machines for producing a current of air ; 

 and there are also holes at proper parts 

 of the edifice, to be occasionally opened, 

 to permit the scoriae and the metal to 

 flow out, as the process may require. 

 Charcoal, or coke, with lighted brush- 

 wood, is first thrown in; and when the 

 whole inside of the furnace has acquired 

 a strong ignition, the ore is thrown in by 

 small quantities at a time, with more of- 

 the fuel, and commonly a portion of lime- 

 stone, as a flux : the ore gradually sub- 

 sides into the hottest part of the furnace, 

 where it becomes fused ; the earthy part 

 being converted into a kind of glass, 

 while the metallic part is reduced by the 

 coal, and falls through the vitreous mat- 

 ter to the lowest place. The quantity of 

 fuel, the additions, and the heat, must bv 



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