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45-8 



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8 KNECHT, On some Constituents of Manchester Soot. 



inflammable, in fact it takes fire spontaneously at a tem- 

 perature of about ioo°, and is then difficult to extinguish. 

 A large plate, containing the extracted soot taken from 

 the drying stove, was seen to contain a little glowing 

 carbon at one point, and this was extinguished. After a 

 short time, however, it began to glow in a different part, 

 and this being also extinguished, another part took fire, 

 and so on, until it was nearly cold. 



The following table gives the amounts of constituents 

 estimated directly : — 



Ammonium sulphate 



Mineral matter (ash) 



Acid constituents 



Benzene extract (hydrocarbons) ... 



Difference (carbon ?) 



1000 „ 



The sample of London soot alluded to above was 

 found to contain considerably less extractive matter than 

 the Manchester sample. The difference was especially 

 noticeable in the case of the benzene extract, which in 

 the London sample only amounted to 1*3 %. 



A sample of soot from Prague, for which I am 

 indebted to Dr. F. Rademacher, showed that the products 

 of the incomplete combustion of their lignite coal are of a 

 very different character. The soot, which is of a brown 

 colour, gave an aqueous extract which was neutral to 

 litmus paper. On evaporating down the solution, calcium 

 sulphate separated out in almost colourless crystals. The 

 acid extract contains only traces of ammonia. Of acid 

 constituents soluble in caustic soda I found 2%, while the 

 benzene extract only amounted to 02 %. 



From the brief and incomplete account which I have 

 brought before you, it is at least evident that the compo- 



