The effect of various factors that might possibly influence the penetration of soda liquor into spruce wood has been examined. It was found that the rate of delignification was the same irrespective of the size of the sample, from a wood-meal of 0.005 mm. particle size up to a limiting chip thickness of about 10 mm. The density of the wood had no influence on the delignification other than that which would be expected from the higher original lignin content of the more dense wood. The presence of moisture in the chips was without result other than that of diluting the liquor, and the addition of wetting agents for facilitating the penetration rate was without significant effect.