according to example 1 were treated with 2 0 kg edta per ton of wood in accordance with the present invention edta was mixed with 140 kg white liquor calculated as effective alkali per ton of wood and the white liquor containing edta was supplied to the circulation digester for pre impregnation of the chips under the same conditions as in test 1 except that at the end of the impregnation the temperature was increased to 167 u00b0 c thereafter digestion of the itc type was performed in accordance with test 1 but at said higher digestion temperature of 167 u00b0 c thus in this experiment no edta metal complexes were removed before the digestion table 3______________________________________ test 9______________________________________edta kg ton wood 2 0digestion temp u00b0 c 167alkali consumption 184yield of wood 43 8kappa number 10 2viscosity dm sup 3 kg 886brightness iso 38 3mn ppm 50mg ppm 245ca ppm 1290cu ppm 38fe ppm 20tensile index knm kg 80beat revolutions pfi 2300drainage resistance u00b0 sr 15 5density kg dm sup 3 660air resistance sec 100 ml 3 5burst index mn kg 6 1tear index nm sup 2 kg 24 5______________________________________ as is clear from the above results the tearing resistance of also this pulp shows a considerable improvement over the reference pulps according to tests 4 and 5 as well as being clearly better than the reference pulps in other respects within the same kappa number interval the results must be deemed surprising also in view of the fact that no withdrawal of liquid containing metals was performed as is evident the manganese content in the pulp has been halved as compared with the reference experiments the pulp obtained from test 1 was subjected to delignification with oxygen.