I. When bleached pulp is refined with the solution of CaO and Na₂SO₃, its α-cellulose content increases about 5%. The addition of NaOH in the cooking liquor, which consists of H₂SO₃ and Ca(HSO₃)₂, results the incrcase in α-cellulose content, but the addition of too much amount of NaOH decreases the yield.
In bleaching of the refined pulp, it is most advantageous to carry it out at low temperature for short time with small quantity of bleaching powder.
2. The refining of unbleached pulp with the solution of CaO and Na₂SO₃, shows the best results. The refined chlorinated pulp is of the largest α-cellulose content and its the bleaching is most easy. The pulp, refined with NaOH solution, contains large amount of α-cellulose, but bleaching is most difficult, and if it is bleached to normal white, the cellulose is over bleached and its content decreases considerablly. The same results are obtained in the case of the solution of CaO and Na₂SO₃.

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