Abstract: A process for the production of a hemicellulose hydrolysate and special pulp through two steps, the first step comprising the prehydrolysis of the material and the second step the dissolving of the lignin contained in the prehydrolyzed material. According to the process the lignin dissolving is carried out by neutral sulphite cooking with anthraquinone or a derivative thereof as a catalyst, the pH of the cooking liquor being initially at least 10.

Abstract: A method of decreasing the viscosity and improving the evaporability of sulfate black liquor from the cellulose cook includes raising the temperature of the black liquor above the cooking temperature so as to split the macro-molecular lignin fraction contained in the liquor. The temperature of the black liquor is maintained at the raised level for 1 to 60 minutes, preferably for 1 to 5 minutes.

Abstract: A method of rapid determination of the concentrations of the total sulphur dioxide and the lignosulphonate present in sulphite pulping process liquors. The lignosulphonates are separated from compounds which form the total sulphur dioxide by means of an ion exclusion column, whereby the filling material of the column consists of a cation exchange resin. The concentration measurements of the sulphur dioxide and the lignosulphonate are carried out from the liquor flow coming out from the separation column by means of UV-method at the wave length of 280 nm. The invention also relates to a method of controlling the sulphite pulping process by determining the total sulphite dioxide concentration in the pulping liquor.