Abstract: In a process for reduction or oxidation of materials in aqueous solution by assing a reagent gas through a finely porous catalyst layer into the solution, bodies of electrically conducting material which in the aggregate have a large surface are brought into electrically conducting connection with the catalyst layer on its side facing the solution in order to increase the rate of conversion of the dissolved material. The conducting bodies are distributed in the solution at least in the region of the catalyst layer and increase the effective surface for the conversion of the dissolved material. The invention is particularly useful in connection with catalyst layers provided with an electrically conducting protective cover through which gas and solution may pass on the side of the catalyst layer facing the solution as disclosed in a related application of the same inventors Ser. No. 500,941 filed June 3, 1983.

Abstract: A method and apparatus are disclosed for determining sulfur dioxide content in a gas sample. The apparatus is a polarographic- type one having first and second tubular chambers. The first chamber has a gas inlet. Gas coming therein causes an electrolyte to circulate around the two chambers with the second chamber having a sensing electrode and a counter electrode therein.

Abstract: Method and apparatus for regenerating etching solutions obtained by chemily processing metallic surfaces, which solutions contain cupric chloride and/or ferric chloride. The apparatus includes between the anode and the cathode a diaphragm or an ion exchange membrane. The etching solution is passed through the electrolysis cell for anodic oxidation of the cuprous and/or ferrous ions obtained by etching of the metallic surface of a workpiece. An effective quantity of activated pulverous carbon particles is suspended at least in the anode compartment of the electrolysis cell, which cell is in communication with an etching chamber in such a way so as to allow circulating flow of solution.