A Jayme reactor was used for oxygen delignification. In all the experiments, the amount of pulp used was 40 g (oven-dry basis). Oxygen delignification experiments were carried out at a consistency of 8%, an oxygen pressure of 0.6 MPa and at a temperature of 100 °C. At the beginning of each experiment, a 0.1% charge (on oven-dry pulp) of MgSO4 dissolved in 300 ml of water was mixed with the pulp, after which a NaOH charge (on oven-dry pulp) was added to the rest of the water. The pulp was then mixed with chemicals, placed in the reactor and oxygen pressure applied. After 60 minutes of delignification, the pressure was released, the reactor opened and the pulp discharged, filtered and washed with four aliquots of 1000 ml deionised water before being stored in a plastic bag for further treatment.