Abstract
Beech wood was cooked with the sulfite liquor (total SO2, 6.92%. combined SO2, 1.52%. max. temp. 140°C) for 10.5, 12 and 12.75 hours, and three unbleached pulps were obtained. The pentosan, lignin, degree of polymerization and its distribution of the pulps were determined. Non-uniformity coefficient was obtained by comparing DPw (viscosity average) with DPn (from osmotic measurernent of the acetone solution of the nitrate). The results were as follows.1. With increase of time for cooking, the lignin content decreased rapidly but the decrease of pentosan content was not so considerable. The increase of the low DP portion of the pulps was marked.2. Non-uniformity coefficient obtained by the measurements of viscosity and osmotic pressure showed decrease(0.89, 0.70, 0.54) with increase of time for cooking. This result was contradictory to the fact that the marked increase of the low DP portion was observed at the later stage of cooking. This would be due to the diffusion of the low DP portion through the membrane in the osmotic cell.
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