THE ELECTRIC FURNACE. 



301 



ciirV)on.s. Tu])osTT lead from the upper portion of the earl)on cylin- 

 der B to the annular chandler R,.just outside and inclosing- the space 

 bounded by the lower electrode C. The g-ases of combustion pass up 

 the center of B, which acts as a Hue, and down by way of the tubes 

 T T to R, where they mingle with air, adiuitted through perforations 

 in the casing, and are consumed, the linal products passing- out through 

 the discharge pipe P. 



The raw material is fed into the mouth of the furnace around the 

 central electrode, and, passing through tlie annular arcing- region at 

 the l)ottom, where it becomes converted into carbide, falls onto the 

 adjustable conical table D. This is provided with a lip around its 

 lower edge and is mounted on a stem .s', which, gearing- with the lever 

 Z, permits of its being raised or lowered according as the operation of 

 the furnace is intermittent or continuous. 



The Denbergh furnace for the manufacture of sulphuric and phos- 

 phoric acids, and also " water-glass," or sodium ortho-silicate, is shown 

 in tig. 7. It consists of an ordinar}" 

 fire-brick structure F, lined at /■ with 

 a refractory material impervious to 

 the gases produced in the reactions, 

 an outlet for which gases is provided 

 at (>. The bod}^ of the furnace is 

 contracted below, as shown, and the 

 outlet R for the fused products is 

 led up within the walls themselves, 

 from the point of lowest level to 

 another point of higher level, which 

 defines the depth of converted ma- 

 terial contained within the furnace. 



The lid L carries a charge inlet i and a hopper H, the feeding being 

 secured mechanicalh' by a reciprocating movement communicated to 

 the piston p, which works in a C3dinder c, carrying- a definite quantity 

 before it at each stroke. The electrodes E E are of carbon, passing 

 thi'ough terminal sockets in which they are capable of motion in a 

 direction corresponding with their axes, which permits of feeding as 

 they wear away, whilst the sockets, in turn, are mounted in a species 

 of swivel joint, which allows the angle of inclination, and consequently 

 the height of the arc, to bo varied at will. 



Roller's arc furnace is of a simple description. It consists of a 

 longitudinal chamber, with massive carbon blocks projecting through 

 the end walls. A series of carbon blocks, supported in line with the 

 terminal electrodes, are arranged along the chamber at regular inter- 

 vals, their number varying according- to the voltage. The arc is tints 

 split up into series, and a numl)er of heated regions are secured in the 

 center of the mass of raw material which is packed around the blocks. 



