Abstract: An information recording disc comprises a guide track, an address signal recording portion arranged in each track turn of the guide track and pre-recorded with an address signal, and a pseudo address signal recording portion arranged in each track turn of the guide track adjacent a corresponding address signal recording portion provided in a track turn of the guide track adjacent thereto. The recording length of the pseudo address signal recording portion is selected approximately equal to the recording length of the corresponding address signal recording portion.

Abstract: A method for purification of a sulfuric acid solution such as, for example, a copper electrolyte which entrains at least one metal ion species selected from the group consisting of antimony ions, bismuth ions, and iron ions and having a sulfuric acid concentration of at least 50 g/liter is disclosed. The method comprises exposing the sulfuric acid solution to a chelating resin possessing aminomethylenephosphonic acid group as a chelate forming group thereby effecting adsorptive separation of the aforementioned at least one metal ion species from the solution. By the method described above, the antimony ions, bismuth ions, and/or iron ions contained as impurities in the copper electrolyte can be easily and efficiently separated out of the system without entailing any ecological problem.