MANUFACTURE OF CARBIDE OF CALCIUM. 



139 



mechanism not unlike that of an arc hxmp. Fig. 1 shows such a 

 furnace made by Siemens and Halske, which the writer worked with 

 in Noi-way about seven years ago. Alternating current at 65 volts 

 2,500 amperes was supplied to three furnaces from a three-phase 



Fig. ].— Intermittent Carbide Furnace. 



alternator. As soon as an ingot about a foot square and 2 feet high 

 was made, the solid copper connections to the two carbon electrodes 

 were disconnected, the tnick withdrawn from the furnace chamber, 

 and another substituted. The ingot is broken up and sorted by hand, 

 the partly-burnt material being returned to the furnace. 



Continuous Furnace. 



In the continuous process there is a chamber lined with magnesite 

 which takes the place of the moveable truck. It has a tapping hole 

 at the bottom, and the raw materials have sufficient excess lime to 

 make the resulting carbide run freely. On this account the carbide is 

 not so good as the best quality made in an Intermittent furnace, but 

 it is very even in gi-ade. Hand-picking is not required, and, if 

 necessary, the ingots can be sold in the form in which they are cast in 

 the moulds. 



