Popel chips were cooked in Kraft liquor modified by anthraquinone (AQ). Ten trials with varying levels of AQ, white liquor and cooking time were completed. It was found that the percent yield decreased by as much as 10 points as the level of AQ was increased. But the Kappa number decreased by only 2 points at the maximum AQ level; therefore, at a consistant Kappa number, the percent yield for the unmodified Kraft pulp would be greater than the modified pulp. Overall pulp strength increased significantly with the addition of 0.05% AQ, as was evidenced by the improvement of strength for the zero revolution refined sample
