Abstract: The continuous process for making crystalline D-sorbitol using a melt crystallizer consisting of a cooled container and a horizontally arranged rotatable shaft equipped with disk elements and mixing parts to form a worm includes evaporating an aqueous D-sorbitol solution at 5 to 200 mbar and at a temperature of 130.degree. to 170.degree. C. in vacuum, advantageously in a thin film evaporator, to obtain a D-sorbitol melt containing less than 0.5 % by weight water; cooling the D-sorbitol melt to a temperature of 5 to 15.degree. C. above a solidification point of the D-sorbitol melt; melt crystallizing the D-sorbitol melt obtained during the evaporating in the melt crystallizer with an average dwell time of 1 to 5 hours to form D-sorbitol crystals and grinding and sieving the D-sorbitol crystals formed during the melt crystallizing of step d) to form a D-sorbitol end product containing more than 90% by weight of a .gamma. modification of crystalline D-sorbitol.

Abstract: A continuous process of removing silica from spent pulping liquors (black liquors) which have been obtained by the alkaline digestion of annual plants. The spent liquor is preconcentrated and contacted with a CO.sub.2 -containing gas. The CO.sub.2 -containing gas is supplied at a rate of 30 to 40 m.sup.3 s.t.p. per m.sup.3 of spent liquor. The precipitated silica is removed from the treated liquor. The silica-containing precipitate which has been separated is diluted and washed with water and causticized by an addition of lime or milk of lime. Solid and liquid phases are separated from each other and the resulting residue is combusted.