Abstract: A method is provided for removal of ferrous ions from a tin-plating electrolyte containing stannous ions in a multi-compartmented electrochemical cell equipped to convert the ferrous and stannous ions to insoluble hydroxides. The hydroxides, in an essentially air-oxygen free environment, are separated by selectively dissolving the ferrous hydroxide in an acidic solution and the undissolved stannous hydroxide in the tin plating electrolyte.

Abstract: An electrode composed of a current element and a fiber element suitable for operation at low voltage and high amperage is disclosed.

Abstract: Process and equipment for manufacturing salts of metals, particularly nickel hypophosphite, are disclosed.

Abstract: Methods for preparing hypophosphorous acid are disclosed comprising contacting an insoluble anode with an aqueous solution of hypophosphite anions and applying a current through the insoluble anode to a cathode in electrical contact with the aqueous solution to generate H+ ions in the aqueous solution thereby forming a hypophosphorous acid solution.

Abstract: An electrochemical process and equipment for preparing iodides, e.g. hydriodic acid (HI), iodide salts and other iodide compounds, substantially free of iodine, are disclosed.

Abstract: Process and equipment for reforming and maintaining the chemistry of an electroless metal bath, particularly an electroless nickel bath is disclosed.

Abstract: Oxidation and reduction reactions are carried out in a continuous aqueous solution having an acidic part and an alkaline part formed by electrolysis and electrodialysis of an acidic electrolyte separated by a cation permeable membrane from an alkaline electrolyte containing a soluble anion of an acid whereby hydrogen ions are electrotransported from an acidic electrolyte through a cation permeable membrane into said alkaline electrolyte to form the acidic part. Reactions are carried out in the acidic or alkaline part or simultaneously or successively in the acidic and alkaline parts by adding reactants to said alkaline electrolyte and passing electricity through said electrolysis and electrodialytic process. Chromium.sup.+6 in the alkaline part is reduced to chromium.sup.+3 in the acidic part by addition of sulfur dioxide to the alkaline part and the chromium.sup.+3 is precipitated by hydroxyl ions in the alkaline part.

Abstract: Complexes and salts of metal cations in aqueous solutions are electrodialytically converted into a solution of acids substantially free of metal cations and insoluble metal hydroxides. Metal cations are insolubilized by hydroxyl ions formed in a catholyte while anions are electrotransported from the catholyte and converted into a solution of acids by hydrogen ions formed in an anolyte of an electrodialytic process. The conversion process is carried out electrically without the electrotransport of metal cations and is especially useful for reforming solutions of acids that form complexes when etching and finishing metal surfaces.

Abstract: Complexes and salts of metal cations and acid anions are electrodialytically converted into insoluble hydroxides of the metal cations and acids of the anions. The conversion is effected without the electrotransport of metal cations by insolubilizing the metal cations with hydroxyl ions formed in a catholyte separated by a cation permeable membrane from an anolyte and converting anions of alkali salts formed in the catholyte to acids in the anolyte. The process comprises (a) feeding a solution of a metal complex or salt to a catholyte containing alkali cations; (b) forming hydroxyl ions in the catholyte to form insoluble metal hydroxides and alkali salts of acid anions; (c) separating the insoluble hydroxide from the catholyte; (d) feeding the separated catholyte to the anolyte whereby alkali cations are electrotransported from the anolyte to the catholyte.

Abstract: An alkali hydroxide solution of a metal hydroxide or metallic oxide acidic is separated into a solid metal hydroxide or metallic oxide acidic and a solution of alkali hydroxide by feeding the alkali solution to an electrolyte comprising a soluble anion of an acid and controlling the pH of the electrolyte to insolubilize a metal hydroxide or metallic oxide acidic by electrotransporting alkali cations from the electrolyte through a cation permeable membrane into a catholyte and converting the alkali cations to a solution of alkali hydroxide. Sodium hydroxide etchants of aluminum containing sodium aluminate are continuously converted to aluminum hydroxide and a solution of sodium hydroxide.

Abstract: A solution, sol or colloidal dispersion of a substantially water insoluble metal hydroxide or acid and an alkali metal hydroxide are electrodialytically converted to a solid substantially water insoluble metal hydroxide or acid and a solution of the alkali metal hydroxide substantially free of the water insoluble metal hydroxide or acid. The conversion is effected by electrodialysis and electrotransport of an alkali metal cation from the solution, sol or dispersion through a cation permeable membrane into an aqueous alkali hydroxide solution and by using a water soluble anion of an acid to vary pH of the solution sol or dispersion to insolubilize the water insoluble metal hydroxide or acid. Sodium hydroxide etchants of aluminum are continously converted to solid aluminum hydroxide and aqueous sodium hydroxide free of aluminum hydroxide.

Abstract: A multivalent metal hydroxide is separated as a solid from an alkali hydroxide or from another multivalent metal hydroxide in an electrodialytic cell. The separation process is regulated by varying the pH or concentration of alkali hydroxide in a feed compartment electrolyte by matching the rate alkali cations are fed and removed from the electrolyte. As a result, one multivalent metal cation separates as a solid in the feed electrolyte or one multivalent cation separates as a solid and one multivalent cation is ionically mobile and electrotransportable from the electrolyte. This electrodialytic method can be used to continuously regenerate sodium hydroxide etchants containing dissolved aluminum, when the dissolved aluminum is removed from the etchant as a solid and the sodium hydroxide is returned as a solution for etching.

Abstract: Multivalent metal cations in aqueous solution are electrotransported efficiently and with high capacity through cation permeable membranes into an aqueous solution containing a sulfonate ion which makes possible a simple electrodialytic process for conversion of all salts of multivalent metal cations into the respective acids or halogens of the anions of the salts and into water soluble salts or water insoluble salts or ionically immobile compounds of the multivalent metal cations. The use of a sulfonate ion the acid of which in a one normal solution would have a pH no greater than three (3) prevents fouling of the membrane and makes electrodialytic conversion of especially salts of barium, strontium, calcium and lead simple, efficient and with high capacity without the formation of undesirable products of electrolysis at the cell anode or cathode.

Abstract: The ends of flexible plastic tubes, particularly of relatively thin thickness, are closed with a cylindrical header or end plug over which an end of the plastic tube is fitted. A fluids connection between the wall of the plastic tube and the cylindrical header or plug is made by press fitting over the connection area a plastic ring smaller in diameter than the outside diameter of the plastic tube within the elastic limit of the plastic ring. Preferably the header and/or end plug have circumferential grooves or depressions into which groove or depression the wall of the tube is fitted or depressed, preferably by multi-turns of plastic threads. For corrosive and oxidizing environments the header, plug, plastic tube, sealing rings and depressing thread are composed of perfluorocarbon polymers.

Abstract: An electrolytic purification process useful for contaminated solutions of oxygen-sensitive organic dyes and other such sensitive organic materials and metal chelates and complexes of organic materials involves applying an electrical potential to said solutions in an intermediate or feed compartment separated by cation permeable membranes from an anolyte compartment having an anode and an acidic aqueous anolyte and from a catholyte compartment having a cathode and an aqueous catholyte whereby the impressed electrical current causes metal cations to be electrotransported through the cation permeable membrane into the catholyte and the solution of oxygen- or hydrogen-sensitive organic material is purified without exposure to the anode or oxygen formed at the anode or to the cathode or hydrogen formed in the catholyte compartment.

Abstract: A multicompartmented cell suitable for use as electrochemical and chemical reactor cells is formed with a freely-extendible tubular membrane which is a thin-walled, preferably ion selective permeable, membrane sleeve which from a dry condition tends to expand and lengthen upon hydration. An end plug fastened at one end of the membrane provides fluids closure whereby the closed membrane end with its end closure is free to move, i.e., is unattached. A cell head to which the other end of the membrane is connected, together with the membrane and the end plug define a compartment. The cell head is provided with means for ingress and egress of fluids to and from such compartment and can also be provided with electrical access to an appropriate electrode. External to the membrane sleeve is a suitable containing means spaced from the membrane to form a compartment outside the membrane, the containing means being sufficient in size to accommodate the membrane in expanded and lengthened condition.

Abstract: Metal stripping solutions of alkaline cyanide and organic acid stripping agents used to strip metal coatings from steel or other substrates are restored for reuse. The process is a membrane electrochemical process wherein an electric current is passed through an electrochemical cell having a membrane separating the metal strip solution from oxygen formed at the cell anode while the strip solution is restored by removal of stripped metals on the cell cathode as electroplatings. The process restores spent strip solution without producing a toxic waste and reduces potential hazards of handling and shipping. The stripped metals are recovered as metals for use in electroplating and other processes.

Abstract: Salts of multivalent cations in aqueous solution, with or without admixture with salts of monovalent cations, are converted into the respective acids or halogens of the anions of the salts and into water insoluble salts or ionically immobile compounds of the multivalent cations. The conversion is effected by electrodialysis and electrotransport of the multivalent cations through a cation permeable membrane into aqueous solutions containing both agents that insolubilize or ionically immobilize the multivalent cations and a soluble salt of an acid, which acid in a one normal solution would have a pH no greater than three and forms water soluble salt with the multivalent cation. The use of the added salt in the solution into which the multivalent cations are electrotransported minimizes fouling of the membrane and makes the electrodialytic conversion efficient and with high capacity.

Abstract: By using an aqueous solution of inorganic carbonate, bicarbonate and/or hydroxide as the catholyte in an electrodialysis process, acids containing a multivalent metal in the anion are prepared substantially free of anionic impurities, substantially pure electroplating-type acids with a multivalent metal in the anion such as chromic, molybdic and tungstic acids are prepared from salts of such acids and multivalent metal cations are separated from anions containing sulfur, phosphorus, halogen or carbon in aqueous solutions such as found in rinse waters from electroplating processes.

Abstract: The use of aqueous inorganic carbonates or bicarbonates as the catholyte in the electrolytic purification of chromium plating solutions permits the cell to operate at a high capacity and a high efficiency without adversely affecting the oxidation state of the chromium ions in the solution.