The natron process for delignification of aspen, despite the somewhat higher admixture of lignin in the pulp, could be more suitable for production of cellulose, in comparison with the sulphate process: the obtained pulp (the so-called “semichemical pulp”) may be used for the production of such paper fibre materials, for which the lignin content is permissible, for example, for packing paperboard; the cooking liquor has a lower content of deep destruction products, which get to waste water; the formation of the unpleasant sulphur organic compound odorants is prevented.