Abstract: A process for the simultaneous production of dicarboxylic acids and diamines from a) polymers based on polyamides of dicarboxylic acids or their derivatives with diamines, orb) compositions containing essentially such polymers, by splitting these polymers into their monomeric constituents, comprises treating these polymers or compounds with a base in alcoholic medium, and subsequently converting the resulting dicarboxylate salts electrochemically into the corresponding dicarboxylic acids and bases.

Abstract: A process is described for preparing metal phthalocyanines by reacting orthodinitriles dissolved or suspended in organic solvents or pulverulent mixtures of ortho-dinitriles with anhydrous ammine-metal carboxylate salts or metal-aminocarboxylic acid complexes without alkaline or chloride-containing additaments using an ortho-dinitrile excess of from 0.1 to 5% by weight.

Abstract: Alkali metal sulfates are electrolyzed to more concentrated solutions of alkali metal hydroxide and sulfuric acid by using a three-compartment electrodialysis cell at temperatures of .gtoreq.70.degree. to .gtoreq.150.degree. C. and current densities of from 0.5 to 15 kA/m.sup.2 using an anion exchange membrane whose polymeric ion exchange matrix comprises a styrene/divinylbenzene copolymer containing very strongly basic quaternary ammonium groups and a hydronium ion blocker, on whose central compartment side is an ion exchange layer or membrane containing tertiary or secondary amino groups.

Abstract: A biological reactor which is operated using microorganisms and/or enzymes and used for the oxidative conversion of organic compounds, and in which the organic compounds to be converted are employed in the presence of a biocatalyst in the reactor space (4) (anode space) and the enzymes are regenerated at a polarized electrode (1), the polarization of the electrode (1) being effected by means of a catalyst electrode (2) which is separated from the reactor space (4) by a polyelectrolyte (3) and is located in an electrolyte space (5), wherein the electrode (1) is prepared from an electrically conductive carbon material which has been partially oxidized on the surface at a potential .epsilon..sub.h of from +1.3 to +10 V in an aqueous oxygen-containing mineral acid.

Abstract: Metal ions are removed from process wastewaters by using an electrically conducting, cathodically polarized filter-aid layer whose potential is at least 50 mV more negative than the redox potential of the metal ions to be removed, by passing the metal ion-containing water through the filter-aid layer and periodically renewing the filter-aid layer at intervals of from 2 to 180 minutes by backwashing, classifying and precoating processes.

Abstract: A metal/metal oxide electrode for determining chlorine in aqueous solutions comprises a metallic tantalum core on which there is non-porous tantalum suboxide.

Abstract: A redox electrode for determining nitrous acid and nitrosyl compounds in aqueous, acidic solution consists of a metallic conductor on which an n-conducting metal oxide surface is present.

Abstract: Oxidizable for organic and/or inorganic compounds in waters are subjected to catalytic degradation using a catalyst applied to an oxygen-storing inert carrier, for example of graphite, coke, a non-gassing coal or active carbon. The carrier used is coated with a cationic dye complexed with heteropolyacids and/or polyacids and/or salts or metal acids of subgroups V to VIII.The advantages of the process include the prevention of biological growth on the catalyst surface by the biocidal dye cation and the avoidance of calcium and magnesium deposits on the catalyst surface through the presence of the cationic solid.

Abstract: A process for the preparation of a water soluble food-grade diaminotriphenylmethane colorant containing from 2 to 4 sulfo groups, comprising anodically oxidizing the corresponding leuco compound in an electrolysis cell divided into an anode space and a cathode space in the presence of from 0.01 to 2% by weight, based on the solution being oxidized, of a C.sub.2 -C.sub.4 -alkanol, urea, a urea derivative or a mixture thereof, at a potential .epsilon..sub.h .ltoreq.1250 mV and at a temperature .ltoreq.+40.degree. C. The colorants obtained are produced in high yield and are of food quality.

Abstract: Wastewaters are subjected to an oxidative treatment with a carbon-containing catalyst and an oxidizing agent by a process in which the carbon carrier used, e.g. graphite, coke or active carbon, is subjected to anodic oxidation in an aqueous mineral acid and then doped with molybdenum(Vl) and/or tungsten(VI) and/or vanadium(V) compounds.

Abstract: In a fuel cell which has an activated carbon-containing anode and an activated carbon-containing cathode and is preferably used for the oxidative treatment of waste waters containing oxygen or oxygen-containing compounds, the cathode has been subjected to partial anodic oxidation in a mineral acid at a potential .epsilon..sub.h of from +1.3 to +10V and then doped with molybdenum(VI) and/or tungsten(VI) and/or vanadium(V) compounds, and the anode has been subjected to partial anodic oxidation in an aqueous mineral acid, cathodically reduced in an aqueous mineral acid and then impregnated with cobalt hydroxide and/or nickel hydroxide and/or copper hydroxide and/or zinc hydroxide, the anode and the cathode being separated by a porous polyelectrolyte through which the waste water flows.

Abstract: Aqueous solutions of hydroxylamine are prepared from aqueous hydroxylammonium salt solutions by electrodialysis by a method in which the aqueous hydroxylammonium salt solution is fed into the middle zone of an electrolysis cell, which is divided into a cathode zone, an anode zone and a middle zone by means of semipermeable membranes, and is electrolyzed, and the catholyte used is an alkali metal hydroxide solution containing ammonia and/or amines.

Abstract: Aqueous solutions of hydroxylammonium carbonate are prepared from aqueous hydroxylammonium salt solutions by electrodialysis by a method in which the aqueous hydroxylammonium salt solution is fed into the middle zone of an electrolysis cell, which is divided into a cathode zone, an anode zone and a middle zone by means of semipermeable membranes, and is electrolyzed, and the catholyte used is an aqueous solution of an ammonium carbonate or an alkali metal carbonate or of one of the corresponding bicarbonates.

Abstract: Blue iron hexacyanoferrate-III pigments are produced by a process wherein complex iron-II hexacyanoferrate-II (Berlin white) is prepared by electrolysis of an aqueous catholyte solution containing (a) an iron-II salt, (b) an alkali metal salt, an ammonium salt or a mixture of these, and (c) hydrogen cyanide, in an electrolysis cell in which the anode chamber and cathode chamber are separated by an ion exchange membrane, using an electrically conductive aqueous liquid in the anode chamber, and the iron-II hexacyanoferrate-II obtained is then converted to the blue pigment.The process gives Berlin white, which is substantially free from salt, in high yield and high purity. Pollution caused by the process is very low, since only a small amount of salt is produced. Compared with the corresponding blue pigments produced by prior art processes, the pigments obtained give purer colorations with better gloss, and are of higher color strength.

Abstract: Blue iron hexacyanoferrate-III pigments (I) are prepared by anodic oxidation of metallic iron in hydrogen cyanide, or a reaction medium containing hydrogen cyanide, at pH<7 and at an anode potential of .ltoreq.0.76 V (measured against a standard hydrogen electrode) to complex iron-II hexacyanoferrate-II compounds (II), which are then oxidized to (I) in a conventional manner. The oxidation of (II) is advantageously carried out with air or oxygen at pH 0-4 and at from 70 to 95.degree. C., but can also be carried out at pH>8.The process gives readily dispersible pigments (I) which are of high color strength and give brilliant, glossy colorations.

Abstract: An electrode for electrolysis purposes, which may in particular be used as an anode for the electrolysis of alkali metal chlorides, contains, in addition to an alloy of niobium with a metal of the iron group, tantalum, tantalum carbide or an alloy of tantalum with metals of the iron group, individually or as mixtures. The surface of the electrode is modified with a metal of the platinum group, especially with rhodium.

Abstract: Metal-free phthalocyanines (PC) are prepared by electrolysis, at inert electrodes, of aromatic o-dinitriles in organic liquids which contain small amounts of dissolved electrolytically conductive compounds, in the presence of hydrogen or of a compound which eliminates hydrogen under the reaction conditions and in the presence of alkaline compounds (as activators). The PC formed may be isolated in the pure form by filtration. The product contains from 90 to 99% of PC. It is used for the preparation of PC-based pigments.

Abstract: In a process for the removal of mercury by treatment with elementary nickel an external voltage is applied to maintain the potential of the nickel at a value which differs from the potential of the reversible hydrogen electrode in the liquid concerned by not more than from -250 mV to +50 mV. The treatment is carried out at temperatures of from 80.degree. to 230.degree. C.

Abstract: An electrode for electrolysis which contains tantalum, tantalum boride, tantalum carbide or an alloy of tantalum with a metal of the iron group in addition to an alloy of tungsten with a metal of the iron group.