Abstract: An improved paper-making hydrous acid filler is prepared by classifying or pulverizing a slurry containing fine particles of hydrous silicic acid, which is obtained by neutralizing sodium silicate with sulfuric acid, by a wet classifier or a wet pulverizer, so that the proportion of particles having a particles size of 1 to 30 .mu.m is at least 80% and the proportion of particles having a particle size of at least 70 .mu.m is not more than 0.4%. The filler has a function of improving the ink receptivity of the paper of the internal additive type and is capable of improving the opacity of the paper after printing.

Abstract: Lignocellulosic material is pulped by a process comprising the steps of: introducing a molecular oxygen-containing gas, such as air, into an alkaline sulfide solution containing NaOH, Na.sub.2 S and at least one cyclic organic compound selected from quinone, hydroquinone, 9,10-diketohydroanthracene and 9,10-dihydroxyhydroanthracene compounds, to oxidize at least a portion of Na.sub.2 S; delignifying the lignocellulosic material with an alkaline sulfide cooking liquor containing the oxidized alkaline sulfide solution at an elevated temperature and; then, recovering the resultant pulp from the delignification mixture.