| 1/00 | Pretreatment of the finely-divided materials before digesting (of waste paper D21C 5/02) |
| 1/02 | Pretreatment of the finely-divided materials before digesting (of waste paper D21C 5/02) with water or steam |
| 1/04 | Pretreatment of the finely-divided materials before digesting (of waste paper D21C 5/02) with acid reacting compounds |
| 1/06 | Pretreatment of the finely-divided materials before digesting (of waste paper D21C 5/02) with alkaline reacting compounds |
| 1/08 | Pretreatment of the finely-divided materials before digesting (of waste paper D21C 5/02) with oxygen-generating compounds |
| 1/10 | Pretreatment of the finely-divided materials before digesting (of waste paper D21C 5/02) Physical methods for facilitating impregnation |
| 3/00 | Pulping cellulose-containing materials (digesters D21C 7/00) |
| 3/02 | Pulping cellulose-containing materials (digesters D21C 7/00) with inorganic bases or alkaline reacting compounds, e.g. sulfate processes |
| 3/04 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides |
| 3/06 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites |
| 3/08 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites calcium bisulfite |
| 3/10 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites magnesium bisulfite |
| 3/12 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites sodium bisulfite |
| 3/14 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides sulfur dioxide; sulfurous acid; bisulfites ammonium bisulfite |
| 3/16 | Pulping cellulose-containing materials (digesters D21C 7/00) with acids, acid salts, or acid anhydrides nitrogen oxides; nitric acid |
| 3/18 | Pulping cellulose-containing materials (digesters D21C 7/00) with halogens or halogen-generating compounds (bleaching cellulose pulp D21C 9/12) |
| 3/20 | Pulping cellulose-containing materials (digesters D21C 7/00) with organic solvents |
| 3/22 | Pulping cellulose-containing materials (digesters D21C 7/00) Other features of pulping processes |
| 3/24 | Pulping cellulose-containing materials (digesters D21C 7/00) Other features of pulping processes Continuous processes |
| 3/26 | Pulping cellulose-containing materials (digesters D21C 7/00) Other features of pulping processes Multi-stage processes |