424 SMITH'S INTERMEDIATE CHEMISTRY 



The ammonia is made into ammonium sulphate. The tar may 

 be used for road-making, as a waterproof material in building, 

 and wherever pitch is applicable. More frequently it is sepa- 

 rated by distillation, and other forms of treatment, and yields 

 benzene C 6 H 6 , naphthalene Ci H 8 , anthracene CiJIio, phenol or 

 carbolic acid C 6 H 5 OH and innumerable other valuable substances. 



Coke Ovens. The by-product coke oven is very much like 

 the plant used for making coal gas. The difference is thac the 

 heating is arranged so as to decompose the volatile matter and 

 cause it to leave as much as possible of its carbon behind. The 

 resulting gas is consequently poor in illuminants, but excellent 

 as a fuel. The ammonia and tar are also diminished in amount, 



but are still produced in paying quan- 

 tities. 



The beehive coke oven (Fig. 106), 

 now largely discarded, is a primitive 

 device of fire-brick, shaped like a bee- 

 hive. It is simply filled with coal, part 

 of which is allowed to burn with a 



limited supply of air. It yields 66 per 

 FIG. 106 , 



cent coke, against 73 per cent from the 



by-product oven. All the volatile matter, with its gas, ammonia, 

 and tar, escapes through an opening at the top, where it burns in 

 a large flame and is wasted. 



Properties and Uses of Coke. Coke is a grey-black, hard 

 material of spongy texture. It burns without flame, and gives a 

 higher temperature than does coal, because no heat is used in 

 vaporizing moisture and volatile matter. On account of these 

 and other properties, it is used in immense quantities in reducing 

 ores of iron and other metals, and in smaller amounts in electric 

 furnace work and in making electric light carbons. 



