THE CONQUEST OF NATURE 



lar purpose, no other known means of producing 

 high temperatures could at all compete with the 

 electric arc. 



There are numerous other operations involving the 

 employment of high temperatures in which electricity 

 is equally preeminent. It is feasible with the electric 

 arc to attain a temperature of about 3,600 degrees 

 centigrade and even this might be exceeded were 

 it not that carbon, of which the electrodes are com- 

 posed, volatilizes at that temperature. Meantime, 

 the highest attainable temperature with ordinary fuels 

 in the blast furnace is only about 1,800 degrees; and 

 the oxy-hydrogen flame is only about two hundred 

 degrees higher. A mixture of oxygen and acetylene, 

 however, burns at a temperature almost equaling that 

 of the electric arc; and this flame, manipulated with 

 the aid of a blowpipe, offers a useful means of applying 

 a high temperature locally, for such processes as the 

 welding of metals. The very highest temperatures 

 yet reached in laboratory or workshop, however, are 

 due to the use of explosive mixtures. Thus a mixture 

 of the metal aluminum granulated, and oxide of iron, 

 when ignited by a fulminating powder, readjusts its 

 atoms to form oxide of aluminum and pure iron, and 

 does this with such fervor that a temperature of about 

 three thousand degrees is reached, the resulting iron 

 being not merely melted but brought almost to the 

 boiling point. Practical advantage is taken of this 

 reaction for the repair of broken implements of iron 

 or steel, the making of continuous rails for trolleys, 

 and the like. 



[314] 



