GB508075A - Improvements in or relating to processes for the purification of etched electrodes - Google Patents

Abstract

508,075. Cleaning by electrolysis. SIEMENS & HALSKE AKT.-GES. Dec. 22, 1937, No. 35554. Convention date, Dec. 22, - 1936. [Class 41] The surfaces of electrodes, particularly electrodes for electrolytic condensers, which are roughened by etching to increase their effective surface area, are cleansed by connecting the electrode as a cathode in a cleansing electrolyte liquid which is substantially free from constituents of the etching bath used prior to cleansing. Preferably, the cathode and anode spaces are separated by a suitable diaphragm, and the process may be supplemented by. a further washing both of anode and cathode spaces, using a liquid free fromforeign ions, such as distilled water, electro-osmotically purified water, glycerine or glycol. The ions removed from the electrode surface may be removed by a colloidal or colloidal-chemical process, which may comprise one of the four following processes, if the acid used for etching is hydrochloric acid: (1) chemical deposition of the chlorine ions freed by the cleansing ; (2) conversion of added substances to complex compounds by the freed ions ; (3) conversion of substances of ionic character into non-ionic substances; (4) absorption of the freed ions and separation into flocculent form by means of colloids. Process (1) may be carried out by adding an appropriate salt or compound to the bath, e.g. silver oxide, mercurous nitrate, lead nitrate or acetate to precipitate silver, mercurous, or load chloride, or by using a counter-electrode of an appropriate metal, e.g. silver, antimony, lead, or bismuth, to give silver chloride, antimony oxychloride, lead chloride, or bismuth oxychloride. Process (2) may be carried out by adding platinum chloride, chromium hydroxide, palladium ammonium-chlorido or palladious chloride, and process (3) by adding benzene diazonium hydroxide to the anode compartment, which is converted to benzene diazonium chloride by the freed chlorine ions, which immediately loses nitrogen to give chlorbenzene. Process (4) may be carried out by adding colloidal ferric hydroxide, aluminium hydroxide, chromium hydroxide, titanium dioxide, or zirconium dioxide. Diaphragm materials specified are leather, parchment paper, viscose, and material sold under the Registered Trade Mark " Cellophane."