IRON ORES. 251 



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vania and other states. The brown hematite is largely worked along 

 Western New England and Eastern New York, in Pennsylvania, and ' 

 many states south and west. The earthy argillaceous carbonate like 

 that of England, and fhe hydrate, are found with the coal deposits, and 

 are a source of much iron. 



The several kinds of ore differ somewhat in the quality of the iron 

 they afford ; but the greatest part of the supposed difference, if we ex- 

 cept the bog ore, depends on the mode of working, and the use of pro- 

 per fluxes in the right proportion. The bog ore (a bog formation) often 

 contains phosphorus from animal decomposition, and generally yields 

 G brittle product, though from its fusibility good for some kinds of 

 casting. 



Mode of Assay. In the assay of ores in the dry way, for economical 

 purposes, somewhat different means are used for the different ores. As 

 in the reduction in the large way, the object is to separate the iron from 

 the oxygen with which it is united, and from the impurities clay, lime, 

 or quartz, if such be present. 



With the pure oxyds, or the carbonate in a pure state, a simple mix- 

 ture of the pulverized ore and charcoal strongly heated in a crucible, 

 will effect a reduction. But it is found better to add carbonate of lime 

 or burnt lime, with clay, or glass, or borax, which fuse into a slag, and 

 besides aiding the reduction, protect the reduced iron from combustion. 

 For specular iron, with 10 parts of the ore finely pulverized, mix as 

 much chalk or limestone, 6 to 8 parts of bottle glass, and sixteenth or 

 a twentieth of the whole by weight of charcoal. For a magnetic iron 

 ore, mix with 10 parts of the ore 12 of glass, and as much chalk, with 

 one part of charcoal ; or, say 3 parts of each burnt lime and burnt clay, 

 and 2£ of charcoal. For a brown hematite, 10 parts of burnt lime, as 

 many of burnt clay, and 3 of charcoal. These proportions, taken from 

 Mushet, are not given as invariably necessary, but simply to guide the 

 experimenter. The fitness of the proportions is to be determined from 

 the result. If the slag is clear and nearly colorless, the reduction is 

 perfect. If dark colored, it contains unreduced oxyd, and too much 

 glass or clay may have been added ; if opaque or porcellanous, too 

 much lime has been used. In the case of an argillaceous ore, the pro- 

 portions of lime and glass should be determined from the proportions of 

 lime and clay in the ore. 



The prepared ore with the fluxes, well mixed, is placed in a crucible 

 lined with moistened and well compacted charcoal dust ; the crucible is 

 filled with charcoal, and closed with a luted lid of fire clay. The 

 heat should be very slowly raised, not using the bellows for three quar- 

 ters of an hour, and finally sustained for a quarter of an hour at a white 

 heat, and then the crucible may be removed and the button of cast iron, 

 after cooling, taken out. 



Reduction of ores. In the reduction of iron ores, the simplest and 

 oldest process consists in heating the pounded ore with charcoalin an 

 open forge, (see beyond, page 237.) By the improved process, the ore 

 is headed in a blast furnace along with charcoal, coke, or mineral coal,. 



What is said of the iron from different ores ? Describe the general 

 mode of assaying iron ores? What is the usual mode of reduction? 

 Describe the blast furnace. 



