ANALYSIS OF ORES OF IRON.

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If we suppose 193 parts of red oxid, and J 93 parts of iron tobe heated together : 193 parts of red oxid are composed of 137black oxid -f- 56 oxigen : 193 parts of ifon, to be converted intoblack oxid, require 71 parts of oxigen; but the second dose,which they can alone attract, consists of only 56 parts, conse-quently 15 parts of oxigen are wanting. This small portion musteither be supplied by the atmosphere, or 55 parts of the ironmust remain uncombincd with oxigen. *

ANALYSIS OF ORES OF IRON.

As to the manner of assaying iron ores, for the purpose ofmaking a calculation of the quantity of metal which may be ex-tracted from the ore, if to be wrought on a large scale, thefollowing methods have been found to answ'er the end very ac-curately :

A certain quantity of the ore which is to be assayed, is firstreduced to small particles, and torrefied bv a gentle heat, notstronger than is required to separate the moisture, and to vola-tilize the sulphur, if the ore contains any, which is easily per-ceived by the smell during the torrefaction. When the moistureand sulphur are separated, four parts of the remaining ore is tobe mixed with an equal quantity of common salt, or muriate ofsoda (which has leert previously deprived of its water of crystal-lization hy stirring it in a flat earthen vessel over fire) and withthe same quantity of a mixture of equal parts of fluor sparand lime, and half a part of charcoal. This mixture is kept redhot in a crucible covered with charcoal, for | of an hour, afterwhich the iron contained in that quantity of ore is found in ametallic state in the bottom of the crucible.

Or, four hundred grains of sub-borate of soda, 40 grains ofslacked lime, and 200 grains of the ore to be assayed, are mixed

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* This is a proof that the proportions of oxigen in the oxids are not yet accuratelyascertained. Indeed, from the. very nature of the experiments, nothing but ap*proximations can be expected.

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