252 



CHEMICAL MANURES. 



TABLE LXXL— PERCEXTAGE OF DIFFERENT XITEOGEX COM- 

 POUNDS PRESENT IN A SERIES OF SAMPLES OF SPENT OXIDE 

 FROM GAS ^YORKS. 



This table shows that the composition of these crude wastes is 

 very irregular. There seems to be no relation between the different 

 forms of nitrogen to be met with therein. Their appearance, smell, 

 and moisture vary exceedingly, some black, others brown, whilst 

 others present a whole play of colours, from deep blue to almost black, 

 to greenish-blue. Sometimes the smell is sulphurous, sometimes 

 cyanic, at other times the smell of benzine or tar predominates. 

 Their consistency is generally pulverulent, sometimes, however, it is 

 damp, pasty, and manipulated with difficulty. All these variations 

 are explained by recalling the origin of the crude, which is a material 

 for purifying coal gas. Ammoniacal compounds, sulphides, cyanides, 

 come from the gas, also naphthalene and tarry matter varying in 

 proportion according to the coal used and also according to the 

 arrangement of the purifiers, because efforts are made to retain the 

 ammonia and the tar before they reach the crude. The matter 

 used to retain the impurities is not always the classic lime and 

 sulphate of iron, green vitriol, which yields sulphate of lime and 

 oxide of iron ; the inert absorbent, generally sawdust, sometimes 

 consists of shavings, or again of earthy matter. The gasworks 

 which delivers the waste has therefore a great influence on its com- 

 position, and this influence farther increases by the care taken in 

 storing the material as it comes from the purifiers. 



