Method for the continuous chemical reduction and removal of mineral matter contained in carbon structures

A process for treating carbon, as herein defined, to reduce the ash content therein comprising treating the carbon with a fluorine acid solution which comprises an aqueous solution of hydrofluorosilicic acid and hydrogen fluoride, such that the available metal oxides are converted to soluble metal fluorides and/or metal fluorosilicates which dissolve in said aqueous solution and separating the treated carbon from the aqueous solution containing the dissolved metal fluorides and/or metal fluorosilicates and wherein the treated carbon is washed with fluorosilicic acid (H.sub.2 SiF.sub.4) to remove metal fluorides and/or metal fluorosilicates from the surface thereof, drying the washed treated carbon at a temperature of from 70.degree. to 140.degree. C. and heating the treated carbon to a temperature of between 250.degree. to 400.degree. C. to remove fluorosilicic acid in the form of HF or SiF.sub.4.