Blectrfcal profcucts Garborun&um. 215 



this gas is thrown off during the burning of a 

 single furnace. This gas is called carbon 

 monoxide, and is caused by the carbon of the 

 coke uniting with the oxygen of the sand. 

 When we consider the vast amount of material 

 that comes away from the furnace in the form 

 of gas it is easy to see why it is necessary to 

 introduce sawdust or some equivalent material 

 into the mixture, in order to give the whole 

 bulk porosity, so that the gas can readily es- 

 eape. We should also expect that after five 

 and one-half tons had been taken away from 

 the whole bulk that it would shrink in size. 

 This is found to be the case. The top of the 

 mass of material sinks down to a considerable 

 ex t t-nt by the end of the time it has been ex- 

 posed to this intense heat. Gradually, after 

 the current has been turned on, the core be- 

 comes heated, first to a red, and afterwards to 

 an intense white heat. This heat is communi- 

 cated to the material surrounding the core, 

 producing various effects in the different 

 strata, owing to the fact that it is not possible 

 to keep a uniform heat throughout the whole 

 bulk of material. Some of it will be " over- 

 done" and some of it " underdone." The ma- 

 terial which lie> immediately in contact witli 

 the core will be overheated, and that, which at 

 one stage was carborundum, has hee>me di 

 integrated by overheating. 



-iliea of the eompound has been driven 



