The daily morning journal and courier., 1898-08-24
THE ELECTRIC FURNACE.
A Wonderful Concentration of Heat in
 a Narrow Compass.

about the electric furnace, says: There have been three distinct eras in the practical application of electricity. The first was characterized by it's use in tel egraphy, the second by it's application to lighting, and the third by it's employ ment in the transmission of power We are now entering upon fourth era, in which electricity may be said to pay back it's debt to the energy which pro- duces it by generating heat in the elec- tric furnace.
 This use of electricity has already revolutionized certain processes in the arts. The heat of the furnace is gene rated by an electric arc such as we see in the case of the arc lights on our city streets. This arc is produced by cur rent of electricity flowing through the intensely heated air between two pieces of carbon The furnace consists of a box or parallelopiped of limestone, having a cavity of similar shape cut into it. The electric current Is led into the cavity by means of pieces, tern1i- nals or electrodes as they are techni- cally called, of hard carbon which pass through holes cut in opposite sides of l the cavity. Then the oxide of the met al which one desires to fuse is mixed with carbon powder and is packed around the carbon terminals and is re- duced by the great heat developed by | the voltaic arc, produced by the electric | current flowing through the cavity | from one carbon terminal to the other. In this way aluminium is produced, and | in similar way carbide of lime, which | on being dropped into water gives forth the gas acetylene in great quan- 1 tity.
 For scientific experimentation the | cavity holds small crucible which is composed of mixture of carbon and magnesia. In this crucible are placed the substances which are to be melted. There is no metal which has not been fused by this furnace. Even platinum and iridium, both of which remain sol i'd in the hottest furnace. such as had hitherto been used, melt like wax in the electric furnace.
 Sometimes a carbon tube is fixed in the latter furnace across the line of di- rection of the carbon terminals, or, in other words, at right angles to them, and so placed that it is about one-half an inch below the intense voltaic arc and about the same distance from the
 bottom of the limestone cavity. In this carbon tube are placed the sub stances which are to be heated. Mate rial can be introduced into one end of this tube, and after it is heated can be drawn off by tipping the tube, without stopping the current in the furnace.
 Tn order to produce diamonds iron is
 melted with a large quantity of carbon
 powder and when the mixture has at
 tained a high temperature-over six thousand degrees Fahrenheit--it is sud-
 denly plunged into cold water or a
 bath of molten lead. The lead, being a
 better conductor of heat than cold wa
 ter, more suddenly deprives the mixture
 of its heat. On examining the slag small colorless crystals of carbon are found, which are identical in their prop
 critics with natural diamonds.
 The electrical furnace has the great
 advantage over other furnaces in it's
 power to localize the heat in narrow
 compass, and the amount of heat we
 can produce in such furnace is almost
 unlimited. An amount of heat energy | equivalent to seven hundred horse-pow- CT has been produced in an electric fur
 mace cavity which was not larger than
 an ordinary tumbler of water. Some
 times a powerful magnet is used to di-
 rect the electric arc upon certain re-
 zion in the furnace. A magnet has the
 property of attracting or repelling an
 electrical current, and the voltaic arc in
 the furnace is such an electrical cur
 rent. With such an arrangement,
 namely, a voltaic arc and magnet, we
 have practically powerful blowpipe,
 which melts glass and the metals like
 wax and vaporizes even the lime walls
 of the furnace. There are a number of
 electric furnaces at Niagara Falls,
 which are used to reduce the oxides of
 metals and to form such substances as
 carbide of lime, from which acetylene is generated and corundum, which is used as grinding agent in the arts
 I have said that the temperature ob-
 tained by the electric furnace is not far from six thousand degrees Fahrenheit. , Since all substances which are availa- ble for making thermometers are melt !. ed by such heat, the question naturally
 arises, how can we measure such a . high temperature? It must be con-
 fessed that we cannot measure it ac-
 curately and can only form an estimate
 Iiiio Cotllilil0 tttu DG l1lddS py 6icClIlCdi
 means. Suppose that a measured l quantity of electricity is sent through
 a thin strip of platinum or a filament 5 similar to that in an Edison lamp. The I heat given out by the glowing platinum 7 or carbon filament depends upon the
 quantity of electricity which we can
 force through it. We can measure this , quantity very accurately and from it
 determine the amount of heat given out
 by the filament. We know that a strir
 of platinum red hot has temperature 5 in the neighborhood of eighteen hun- l dred degrees Fahrenheit, and when il is white hot temperature of thirty
 four hundred degrees. Suppose that we e keep the platinum strip red hot by a g known current of electricity and put a : delicate thermometer at a distance of
 three or four feet from the strip and
 read its indication. We will then ex- , pose the same thermometer to an elec- tric arc lamp, which represents the
 electric furnace, and move it until ii
 reads the same as it did when it was exposed to the red hot platinum strip We shall find that we must move the D thermometer much further from the l. electric furnace, and thus knowing the