Abstract: Production of siliceous precipitates, for example sodium aluminosilicates by decomposition of an alkali metal sulfite solution with a solution of a sulfitic species such as sulfur dioxide, sulfurous acid or a salt thereof. Precipitates having excellent properties are obtained and the co-produced aqueous phase is a solution of alkali metal sulfite which has utility in pulp and paper mills. The process is advantageously carried out in proximity to a pulp and paper making operation wherein the siliceous precipitate may be used as a paper making filler and the alkali metal sulfite solution may be used in the pulping process.

Abstract: A process is provided for the bleaching of wood pulp with hydrogen or sodium peroxide. The process includes the steps of adding to a wood pulp a bleach liquor having an effective amount of hydrogen or sodium peroxide bleaching agent and, by weight of the diluted wood pulp, 0.5 to 6% sodium hydroxide, 0 to 5% sodium silicate, 0 to 1%, preferably 0.02 to 0.05%, magnesium sulphate, and a chelating agent in an amount sufficient to sequester heavy metal ions in the pulp, to produce a pulp consistency of 1 to 16% at a temperature in the range of the bleach liquor freezing point to 25.degree. C., uniformly mixing the bleach liquor with the wood pulp, and immediately thickening the diluted wood pulp to a consistency in the range of 20 to 70% for bleaching of the thickened wood pulp.