Abstract: High-quality coloring carbon black having a specific surface area (S.sub.BET), an area average diameter (D.sub.a) and a pore volume (AV.sub.Hg) which make both the roughness factor (RF) and aggregate factor (AF) as calculated by the following equations, negative values:RF=S.sub.BET -28710/(D.sub.a)+1450AF=AV.sub.Hg +14.times.(D.sub.a)-290where S.sub.BET is the specific surface area (m.sup.2 /g) of the carbon black as measured by a BET nitrogen absorption method, D.sub.a is the area average diameter (m.mu.m) of the carbon black as measured by an electron microscopic measuring method, and AV.sub.Hg is the pore volume (cc/100 g) of the carbon black as measured by a mercury porosimeter, provided D.sub.a is at most 17 m.mu.m.

Abstract: A process for purifying carbon black which contains solid impurities by removing the solid impurities thererom, which process comprises suspending said carbon black uniformly in water to obtain a carbon black aqueous slurry and subjecting the slurry to sieving treatment by an ultrasonic vibration sieving apparatus.

Abstract: A process for producing carbon black in a reaction system comprising a first zone where a heating fuel material and an oxygen-containing gas are mixed, and a high temperature combustion gas stream is formed, a second zone where a hydrocarbon starting material is mixed to the high temperature combustion gas stream to form carbon black, and a third zone subsequent to and down-stream of the second zone, where the carbon black thus formed, is contacted with an activating agent to activate the carbon black, characterized in that steam is introduced as an activating agent to the third zone.