58 CHEMICAL FERTILIZERS 



different conditions, from which it will be noticed that a 

 very great variation in composition exists, due to the methods 

 by which the coal is burnt. 



TABLE 10. 

 ANALYSES OF SOOT (Cohen and Ruston, Leeds). 



Owing to the high velocity of the wind current in the 

 flue from a boiler, the percentage of ash in boiler soot is very 

 high, whilst in the domestic fire grate it is the proportion 

 of tar that is strikingly high. The percentage of nitrogen 

 is much higher in domestic soot than in factory soot, 

 Owing to the high temperatures in the lower portions of the 

 factory chimney, little ammonia is deposited there, but it 

 is condensed higher up the chimney, where lower tempera- 

 tures prevail. Many varieties of domestic soot contain a 

 higher percentage of nitrogen than the particular specimen 

 analysed for Table 10. Even the soot from a foundry 

 using liquid fuel is not entirely devoid of nitrogen. Con- 

 siderable variations also occur, even in ordinary domestic 

 soot, between the soot collected from an ordinary open 

 sitting-room fire and that collected from a kitchen range ; 

 the percentage of nitrogen in soot from a kitchen range is 

 always lower. In the case of an ordinary sitting-room 

 chimney, the richest soot is deposited comparatively low 

 down, about 5 or 10 ft. from the fire ; the soot obtained 

 from regions near the chimney top being of lower nitrogen 

 content. The region in which most of the nitrogen condenses 



