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Kraft pulping with the addition of polysulfide, i.e. polysulfide pulping, is one of the few methods available which can be used to increase the yield and change the properties of kraft pulp. The chemistry of aqueous polysulfide solutions and the concurrent reactions occurring in polysulfide pulping have been studied in a series of investigations by the author and his coworkers. The results obtained are summarized and put in relation to those of other research groups in the same field. The historical background is given by reviewing the literature on polysulfide pulping and polysulfide chemistry respectively. Firstly the ionic composition of aqueous polysulfide solutions, i.e. polysulfide pulping liquors, is discussed. Subsequently the reactions of polysulfide ions in the absence of organic material, the rearrangement between polysulfide ions of different size and the thermal decomposition of polysulfide solutions, are reviewed. Thereafter an account is given of the reactions between polysulfide and the major wood components, lignin and carbohydrates. Finally the preparation of aqueous polysulfide solutions is discussed. (Author)

The report covers three subjects: I. A linear model is proposed which describes the contribution of carbohydrates, lignin and extractives to the specific light-absorption coefficient of pulp and methods are given for the determination of the quantities involved. The specific absorption coefficients of pulp and wood are determined by reflectance measurements on pulp and wood refiner pulp sheets respectively. II. A technique, for the determination of the contribution of lignin, carbohydrates and extractives to the specific absorption coefficient of pulp has been applied to pulps from various sulfite pulping processes. Pulps varying in yield between 90 and 50% have been investigated. III. A technique for the determination of the contributions of lignin, carbohydrates, and extractives to the specific absorption coefficient of pulp has been applied to kraft pulps. The yield range of 90 to 50% has been investigated by using two levels of effective alkali charge., Also includes Meddelande-45.