Transactions . rolysed by the current, and the resultant silicon wouldalloy with platinum; but the little magnesia furnace here de-scribed seems to be wholly free from this objection. It hasbeen used in my laboratory for some months, and temperaturesup to 1100° C. have been developed in it over considerableperiods of time—indeed, it has been held near 1400° C. forabout two hours—without indication, thus far, of any deterio-ration of the platinum. In the section shown, F F are a pair of steel disks, boundtogether, but separated by the inverted thermo-junction, IN, ofthe thermo-electric pyromete
Transactions . rolysed by the current, and the resultant silicon wouldalloy with platinum; but the little magnesia furnace here de-scribed seems to be wholly free from this objection. It hasbeen used in my laboratory for some months, and temperaturesup to 1100° C. have been developed in it over considerableperiods of time—indeed, it has been held near 1400° C. forabout two hours—without indication, thus far, of any deterio-ration of the platinum. In the section shown, F F are a pair of steel disks, boundtogether, but separated by the inverted thermo-junction, IN, ofthe thermo-electric pyrometer. This arrangement permits theobservation and record of retardations in the heating and cool-ing of F F—in other words, the determinations of the coolingcurves of steel—a purpose for which the furnace has been used,thus far, more frequently than in the determination of melting-points. For the latter operation, however, it is also suitable. I RIC-RESIS I w< l. I i i:n kOB I OB L IBOF ITOIU -1 3E. I. Electric-Resistance Crucible-Furnace. (Vertical Section. Actual Size.) Indeed, it was originally designed for use in calibrating tliermo-electric couples by means of the melting-point of copper. Forthis purpose, the method described by Holman* had been found * Pruc. Am. Acad, of Arts and Sci., 1895-6, p. 240; also Technology Quarterly,viii., 1895, p. 300. 570 ELECTRIC-RESISTANCE FURNACE FOR LABORATORY-USE. upon repeated trial to be unsatisfactory, because of the liabil-ity of the copper to oxidation; and this apparatus was devisedto permit the crucible to be filled with an atmosphere composed of equal volumes of carbonic acid and carbonic oxide—a gase-ous mixture which does not oxidize copper,* and, at the sametime, is unlikely to cause deposition of carbon- In such an operation, the mixture of carbonic acid and oxide,or any other desired atmosphere, is introduced through thepipe H, which, as well as the openings I and K, may be tightlypacked, while the cover, C
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
