﻿Manchester Memoirs, Vol. xlix. (1905), No. 14. 5 



acid on the mortar in the chimneys, but the occurrence of 

 this substance in surface snow would appear to indicate 

 that the lime had come out of the coal. The filtrate from 

 the calcium sulphate was of a clear light brown colour, 

 and was found on analysis to contain ammonia equivalent 

 to 107% ammonium sulphate on the weight of the 

 original soot. This extract was not further examined. 



Caustic soda extract. 1000 grms soot were extracted 

 as before with boiling dilute sulphuric acid and washed. 

 The residue was then boiled for three hours with eight 

 litres water and 200 grms. caustic soda. A dark brown 

 liquid resulted, which was filtered off, and the acid con- 

 stituents precipitated by acidulating with dilute sulphuric 

 acid. The product thus obtained amounted to 109 grms. 

 It was of a rich brown colour, and possessed a strong 

 sooty smell. On heating it neither melts nor volatilises, 

 but simply chars with evolution of but little gas. It 

 resists nitration and sulphonation, and is soluble in 

 boiling sodium carbonate. The solution in caustic soda 

 is not precipitated by carbonic acid. In its general pro- 

 perties the substance (which is nitrogenous) would appear 

 to resemble some of those indefinite brown organic sub- 

 stances which are classed as humic acid.* 



A portion of the caustic soda extract, melted in the 

 well known manner with sodium sulphide, yielded a 

 sulphide colour which resembles in its tinctorial properties 

 the best brands of Cachou de Laval, and dyes cotton in 

 absolutely fast shades from a light fawn to a brown black, 

 according to the amount of colour employed. 



Benzene extract. The residue from the caustic soda 

 extract was dried and then extracted with hot benzene. 



* According to Kohler {Die Fabrikation des Russes, p. 13) a brown 

 pigment known as bistre was formerly prepared from the soot which 

 separated as a glossy black coating near the fire. 



