Abstract: Process for preserving the mechanical strength properties of a chemical paper pulp, comprising two treatment stages by means of a peroxidic reagent, with the first stage in an acidic medium and the second stage in an alkaline medium, according to which a treatment by means of a reducing compound is interposed between the two stages.

Abstract: Process for obtaining aqueous hydrogen peroxide solutions by the alkylanthraquinone process, providing a concentrated aqueous hydrogen peroxide solution with a low content of impurities, according to which a continuous addition of acidifying compounds and/or of stabilising compounds is performed, consisting in recycling towards the oxidation unit at least a part of the purge leaving the distillation unit.

Abstract: Process for obtaining purified hydrogen peroxide solutions, consisting in evaporating the crude aqueous hydrogen peroxide solution containing the impurities and feeding by means of the vapour phase produced the foot of a distillation column provided in its lower part with a zone for washing the vapour phase with a small flow of liquid which refluxes in the bottom of the column and which has the same composition as the purified aqueous hydrogen peroxide solution forming the product leaving the column, in drawing off this purified product at a column height such that the draw-off is carried out above the vapour phase washing zone and in collecting at the bottom of the column a residue consisting of the small flow of washing liquid which contains most of the impurities. The washing zone has a diameter which is greater than that of the remainder of the column.Distillation column for carrying out the process.