Chemical engineering . FIG I.— r.\RBON RHEOSTAT This can generally be done within limits where an alternatingcurrent is used, but the apparatus used for the purpose is some-what expensive, so that in experimental work it is often de-sirable to use merely a rheostat. For this method of regula-tion a water rheostat may be used, but it is believed that amore satisfactory apparatus is foimd in the granular carbonrheostat. This consists simply in a trough of fire brick filledwith granular carbon and connected in series with the fur-nace. An ammeter is included in the circuit and a voltmete
Chemical engineering . FIG I.— r.\RBON RHEOSTAT This can generally be done within limits where an alternatingcurrent is used, but the apparatus used for the purpose is some-what expensive, so that in experimental work it is often de-sirable to use merely a rheostat. For this method of regula-tion a water rheostat may be used, but it is believed that amore satisfactory apparatus is foimd in the granular carbonrheostat. This consists simply in a trough of fire brick filledwith granular carbon and connected in series with the fur-nace. An ammeter is included in the circuit and a voltmeterconnected to the furnace terminals, and from the readings ofthese instruments the power generated in the furnace may bedetermined. By increasing or diminishing the amount of car-bon in the rheostat its resistance mav be varied, so that. FIG. 2.—LONG RHEOST.\T, USED FOR BAKING. the amount of energj developed per second in the furnacemay be regulated as desired. When delicate regulation is re-quired it is not desirable to attempt the removal or additionof carbon; instead, the change in resistance by pressure ismade use of. In Fig. I a photograph of a granular carbonrheostat is shown. At the left is part of the carbon to the furnace and the rheostat, while at the right,part of the terminal of the rheostat is shown. The trough is3 bricks, that is, about 27 inches long, and is partly filled withgranular graphitized coke. The three bricks standing on endin the trough are resting on the granular coke and serve in that way for more delicate regulation of the energy devel-oped in the furnace. If the experiments made in the furnace re-quire very delicate regulation of temperature the granularcarbon rheostat should be made long, so that the placing ofa brick or other weight on the carbon produces but a smallch
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectmetallu, bookyear1902
