﻿Manchester Memoirs, Vol. xlix. (1905), No. 14. 3 



volatilised by the heat of the fire, and partly carried 

 away mechanically by the draught. 



Our original idea of ascertaining the composition of 

 coal smoke proper presented difficulties which we did not 

 see our way to overcome, so we chose the next best 

 expedient of subjecting ordinary chimney soot to a more 

 exact examination. The first samples examined were 

 taken partly from chimneys in my own house and partly 

 from other chimneys, but were found to vary so much in 

 composition, that it was ultimately decided to obtain an 

 average sample from a dealer, and this subsequently 

 served for all our quantitative experiments.* 



In consequence of its constant exposure, while in the 

 chimney, to a current of warm air, this soot may have 

 lost some of its more volatile constituents, and these 

 would in that case have escaped observation. Again, it is 

 quite likely that in one and the same stack the compo- 

 sition of the soot will vary according to the distance from 

 the fire, but this question was not gone into. 



The methods employed for separating and isolating 

 the constituents were similar to those which are used 

 in the treatment of coal-tar. The soot was extracted 

 with boiling dilute sulphuric acid, with the object of 

 removing basic constituents ; then with caustic soda, to 

 remove acid constituents and phenols ; and lastly with 

 benzene, to extract the hydrocarbons. Modifications of 

 this mode of procedure were also tried, for the sake of 



# A large proportion of the household soot collected in Manchester 

 is sold to dealers, who in their turn dispose of it for agricultural or 

 horticultural purposes. I am informed that some is sold locally, but that 

 the bulk goes to Kent, where it is used as a manure for hops. Its effective 

 constituent as a manure consists of salts of ammonia. At the same time, 

 however, it acts as an insecticide, and this property is possibly due to the 

 presence of pyridine and allied bases. At any rate it is certain that its 

 value as a manure cannot depend altogether upon the amount of ammonia it 

 contains, as its price (3s. per cwt.) would be far too high in proportion to 

 the percentage (10-15) of the latter. 



