Abstract: An electrode system and method, including a measurement electrode, a reference electrode and a counterelectrode, for measuring hydrogen peroxide concentration in a solution. For the measurement electrode, an electrode made from titanium, zirconium, tantalum or niobium is used.

Abstract: The invention relates to a method for separating plastic particles (P) from a suspension (L), e.g. from a cellulose mass or cellulose pulp suspension, in which the fiber-floc material is broken for loosening the plastic particles (P). In the method, turbulent flows are caused to said suspension (L), by means of which flows the particles (P) to be separated are separated from the remaining mass as the fiber network is decomposing, whereby lighter particles (P) are separated. In the method, the suspension (L) obtained in the previous phase is subjected to such a treatment that a concentration difference is achieved, which prevents the fiber network from reforming and thereby the plastic particles (P) from binding thereto, and a flow (F) is directed to the separation point, where the plastic particles (P) are separated from the suspension (L).

Abstract: Plastic particles are separated from liquid mediums having the same distributed therethrough, in particular cellulose and paper fiber-containing mediums by electrolytic separation. The liquid medium is introduced into a container provided with an anode, a cathode and a reference electrode, with the plastic particles being separated from the liquid medium by controlling the potential of the anode and the cathode so that the potential of the anode is at most 2800 mV S.C.E., preferably +1200 to -300 mV S.C.E., and the potential of the cathode is at least -3500 mV S.C.E., preferably from +120 to -2100 mV S.C.E. The control of the potentials of the electrodes is effected to such ranges that gas production is selectively provided on the electrodes for cleaning thereof.

Abstract: A procedure for controlling cellulose digestion by measuring activity of chemicals essentially influencing the cellulose digestion and which are present in a cellulose digester. Feeding of chemicals to be added into the cellulose digester is controlled on the basis of the measurement results. The measurement is carried out by placing, in the cellulose digester, one or several measuring electrodes and reference electrodes, and a current-supplying counterelectrode. Current is supplied to the thus-established circuit from a current source, in a manner such that the voltage across the measuring electrode and the reference electrode, in other words the electrochemical potential of the measuring electrode, is substantially constant. The current intensity corresponding to such potential is directly proportional to activity of the chemicals in the cellulose digester. A method for measuring the cellulose digestive activity is also provided in accordance with the present invention.