solutions 11 and 18 the electrical potential of nickel anode 20 relative to a standard calomel electrode 28 is measured by voltmeter 105 the flow rate of solutions through the system is adjusted to provide a sufficient dwell time for the reaction to take place in tower 103 the emf required for the process of the invention as determined by the potential of the anode with reference to a standard calomel electrode may vary from about 0 2 volts to about 0 6 volts with about 0 4 volts being preferred the cell current automatically adjusts to oxidize all species passing through anode compartment 15 which are reactive at the electrical potential selected particularly the ferrocyanide which is completely reactive in this potential range thus the current magnitude is dependent on the concentration of ferrocyanide entering the cell and on the concentration of oxidizable organic species principally from lignin extracted from the pulp at the anode potentials relative to a standard calomel electrode contemplated by the invention no oxygen is generated at the anode 34 kappa 34 number referred to herein is a measure of residual lignin in a lignocellulosic material and is determined according to tappi standard t236 os 76 pulp 34 viscosity 34 or 34 viscosity 34 referred to herein is a measure of the degree of polymerization of cellulose in.