﻿4 KNECHT, On some Constituents of Manchester Soot. 



convenience. Thus, in one series of experiments, the soot 

 was first extracted with benzene, and the extract, after 

 evaporating off the solvent, treated with sulphuric acid 

 and then with caustic soda. In another case the soot 

 was extracted with benzene, and this extract was, treated 

 with caustic soda only (previous experience having shown 

 that practically none of the basic constituents were taken 

 out by the benzene). The benzene extract was separated 

 from the soda lye, and from the black tar which formed a 

 middle layer, and in this case was the only portion further 

 worked on. 



Aqueous extract. In all the samples of Manchester 

 soot which came under examination, it was found that the 

 aqueous extract showed a strongly acid reaction, due to 

 the presence of free sulphuric acid, which amounted 

 on an average to about one per cent.* The aqueous 

 extract contains practically all the ammonia and pyridine 

 bases. By a tedious process of extraction, I succeeded in 

 isolating from it both ammonium sulphate and ammonium 

 chloride by purely mechanical means. 



Sulphuric acid extract. 500 grms. soot were boiled 

 for several hours with 4 litres dilute sulphuric acid, 

 filtered, washed, and the united filtrates evaporated down 

 to a quarter of the original bulk. A considerable quan- 

 tity of a crystalline deposit thus separated, amounting to 

 9*5 grms. This was found on examination to consist of 

 an impure calcium sulphate. It is noteworthy that the 

 same deposit was obtained with all the Manchester 

 samples worked on as well as with the Prague sample. 

 It might have been taken for granted that the presence of 

 calcium sulphate was due to the action of the sulphuric 



* A sample of soot which came from a suburb of London (E.) also 

 yielded a strongly acid aqueous extract, whereas a sample which I obtained 

 from Prague (lignite coal) gave an extract which was neutral to litmus 

 paper. 



