​SOOT (O. Eng. sot, cf. Icel. sot, Dan. sod; possibly from root sed, to sit), the black substance produced in the process of the combustion of fuel and deposited in finely granulated particles on the interior of chimneys or pipes through which the smoke passes. Soot is a natural nitrogenous manure (q.v.), and its value depends on the ammonia salts contained in it.