. Electrical world. best therequirements of a carrier of the arc flame, since it is well con-ducting, stable at all temperatures, very plentiful in nature, andgives a white arc of high efficiency. Pure magnetite, however, is not quite satisfactory, since its effi-ciency is not very high, hardly twice as high as that of the ordinarycarbon arc: and the arc tends to flicker and the rate of consumptionof the electrode is rather high; as high as % in. per hour. This,while very much lower than the rate of consumption of flame carbons,of I in. to 2 in. per hour, would still give only 50 to 60 hours l
. Electrical world. best therequirements of a carrier of the arc flame, since it is well con-ducting, stable at all temperatures, very plentiful in nature, andgives a white arc of high efficiency. Pure magnetite, however, is not quite satisfactory, since its effi-ciency is not very high, hardly twice as high as that of the ordinarycarbon arc: and the arc tends to flicker and the rate of consumptionof the electrode is rather high; as high as % in. per hour. This,while very much lower than the rate of consumption of flame carbons,of I in. to 2 in. per hour, would still give only 50 to 60 hours lifewith the standard size of electrode adopted for the magnetite arclamp, of 8 in. length. Therefore, with the magnetite as carrier ofthe arc flame are incorporated other substances in small quantitiesas arc-steadying compounds—titanium compounds for increasing theethciency, etc. In the manufacture of these magnetite arc electrodes, by partiallyreducing the material to metal, a greater density is produced and so a. FIG. 4.—M.^GNETITE STREET LAMP. greater amount of material with the same size of electrode, whichgives a longer life. Such partial reduction, however, has the disad-vantage that when not carried far enough it leaves the electrodeporous and of relatively short life, while when carried too far, thelight tends to unsteadiness, turns faint and blue whenever the arcstrikes metal and in this case scintillating sparks are thrown off,which may crack the outer lamp globe. A much better method ofproducing electrodes was found by not reducing the material, butadding a restrainer; that is, a substance which added to the electrodematerial in small quantities reduces the rate of , without any loss of efficiency, rates of consumption of 20o 30 hours per inch are produced, which give a life of 150 to 200-urs for the 8-in. electrode. With very little sacrifice of efficiency:. life of 500 to 600 hours is produced and such an electrode has aboutthe same life as an
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectelectri, bookyear1883
