Abstract: For bleaching natural chalk, an aqueous suspension consisting of 50 to 80% by weight fine-grained natural chalk and 50 to 20% by weight water and containing 0.1 to 1.5% by weight, based on the dry weight of the chalk, of a dispersant and optionally containing a hydrogen peroxide stabilizer or activator or a salt of hydrogen peroxide with a divalent metal is prepared, the suspension is wet ground to reduce the particle size until about 9/10 of the particles have a grain size of <4, the suspension is mixed with hydrogen peroxide or a salt of hydrogen peroxide with a divalent metal at temperatures between 50.degree. and 99.degree. C. and at a specific pH-value or at an alkaline pH, respectively, and stirred intensively until it is mixed and foaming commences, the suspension is allowed to stand until foam formation is complete and then the foam formed is separated with the dark particles contained therein.

Abstract: The present invention provides a process for cross-linking non-polar polymers in a high-frequency electric alternating field with the use of a peroxide as cross-linking agent, wherein the cross-linking agent used is a peroxide of the general formula: ##STR1## in which R.sup.1 is a hydrogen atom, an alkyl radical containing up to 4 carbon atoms or a phenyl radical optionally substituted by halogen atoms or alkyl radicals containing up to 4 carbon atoms;R.sup.2, R.sup.3, R.sup.4 and R.sup.5, which can be the same or different, are hydrogen atoms or, together with the carbon atoms to which they are attached, represent o-phenylene radicals;A is a straight-chained or branched alkylene radical containing up to 5 carbon atoms or a straight-chained or branched alkylene radical containing up to 5 carbon atoms or a phenylene radical and;R.sup.6 is a hydrogen atom or a radical of the general formula ##STR2## in which R.sup.1, R.sup.2, R.sup.3, R.sup.4 and R.sup.5 are identified as above.

Abstract: A process for the distillative separation of tertiary alkyl hydroperoxides of the formulaR--OOHwhereinR is a tertiary alkyl group with 4 to 6 carbon atoms from the corresponding di-tertiary alkyl peroxides resulting during their preparation, which process comprises neutralizing the reaction mixture resulting during the preparation of the tertiary alkyl hydroperoxide, subjecting same to vacuum distillation in the presence of water at a temperature of less than about 45.degree. C. and recovering the purified tertiary alkyl hydroperoxide as a bottoms product.

Abstract: The present invention provides a process for the continuous production of dialkylperoxydicarbonates of the general formula: ##STR1## in which R stands for the same or different, straight-chained, cyclic or branched alkyl radicals containing 6 to 18 carbon atoms, by the continuous reaction of a chloroformic acid ester of the general formula: ##STR2## wherein R has the above-given meanings, in an aqueous medium with hydrogen peroxide and an alkali metal hydroxide at a temperature of from -10.degree. C. to +50.degree. C. in at least two reaction zones connected in series and continuous isolation of the dialkylperoxydicarbonate formed from the solvent-free reaction mixture with the use of a centrifuge, wherein the reaction is carried out in the presence of a surfactant and the dialkylperoxydicarbonate formed is separated in molten form from the alkaline reaction mixture heated to or just above the melting temperature of the dialkylperoxydicarbonate.