. Transactions. Magnesia Fire-Clay Gruphite Kryptol Fig. 6.—Electric-Resistance Furnace. constructed. This refers to furnaces in which the heating-rate is under such control as to permit their use for scientificinvestigation. A foreign carbon-resistance furnace was im-ported, but proved unsuitable in the work. After consider-able experimental work the furnace shown in detail drawing inFig. 6 and in perspective in Fig. 7 was built, and gave most ex-cellent service. The resistor is kryptol. The cross-section andlength of the resistor cylinder are designed for a 115-volt directcurrent. The curren
. Transactions. Magnesia Fire-Clay Gruphite Kryptol Fig. 6.—Electric-Resistance Furnace. constructed. This refers to furnaces in which the heating-rate is under such control as to permit their use for scientificinvestigation. A foreign carbon-resistance furnace was im-ported, but proved unsuitable in the work. After consider-able experimental work the furnace shown in detail drawing inFig. 6 and in perspective in Fig. 7 was built, and gave most ex-cellent service. The resistor is kryptol. The cross-section andlength of the resistor cylinder are designed for a 115-volt directcurrent. The current-consumption is from 10 to 30 amperes. 770 CONSTITUTION AND MELTING-POINTS OF PiG. 7.—Electric Furxack. Kryptol. \ I BH 1 Fig. 8.—Ei-kctric Fuhxace. Platinum \\ ire. CONSTITUTION AND MELTING-POINTS OF COPPER-SLAGS. 771 dependent upon the temperature to be obtained. With thelatter current the limit of the platinum-rhodium thermo-coupleis reached in about 4 hr., if the furnace is protected againstexcessive radiation. The essential features ^^ of the furnace arethe following: (1) Two concentric cylindrical tubes, the innerone of which forms the heating-chamber, made of either mag-nesia (calcined magnesite furnished by the Harbison-WalkerCo., Pittsburg) or alundum, and the cylindrical space betweenwhich, when filled with a resistor like kryptol, becomes theresistor cylinder. (2) Uniform and continuous contact of theresistor on its whole cross-section with the lower graphite elec-trode plate. (3) A resistor of uniform cross-section throughoutits length. (4) The positive and firm insertion of the tubes inthe electrode plates, thus maintaining the resistor chamber
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Keywords: ., bo, bookcentury1800, bookdecade1870, booksubjectmineralindustries
