OSI 4937 International Standard INTE RNATiONAL ORGANIZATION FOR STANDARDIZATION MEXAYHAPOAHAR OPrAHM3AUMR nO CTAHAAPTM3AWU ORGANISATION INTE RNATIONALE DE NORMALISATION Steel and iron - Determination of chromium content - Potentiometric or visual titration method Aciers et fontes -- Dosage du chrome -- Methode par titrage potentiométrique ou visuel First edition -- 1986-12-15 ISO 4937-1986 (E) UDC 629.13/.14 : 543.24/.25 : 546.76 Ref. No. 1SO 4937-1986 (E) Descriptors : steels, iron, chemical analysis, determination of content, chromium, potentiometric methods, volumetric analysis. Price based on 8 pages Copyright International Organization for Standardization ted without license from IHS NotforResale Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (ISO member bodies). The work of preparing international Standards is normally carried out through ISO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaison with IsO, also take part in the work. Draft international Standards adopted by the technical committees are circulated to the member bodies for approval before their acceptance as International Standards by the ISO Council. They are approved in accordance with ISO procedures requiring at least 75 % approval by the member bodies voting. International Standard ISO 4937 was prepared by Technical Committee ISO/TC 17, Steel. Users should note that all International Standards undergo revision from time to time and that any reference made herein to any other International Standard implies its latest edition, unless otherwise stated. @ International Organization for Standardization, 1986 Printed in Switzerland Copyright InternationalOrganization for Standardization Not for Resale ISO 4937-1986 (E) INTERNATIONAL STANDARD Steel and iron -- Determination of chromium content - Potentiometric or visual titration method 1 Scope and field of application 4.1 Urea. This International Standard specifies a method for the deter- mination of chromium in steel and iron by potentiometric or 4.2 Perchloric acid, g approximately 1,67 g/ml. visual titration. 4.3 Hydrofluoric acid, g approximately 1,15 g/ml. The method is applicabie to chromium contents between 0,25 and 35 % (m/m). 4.4 Orthophosphoric acid, g approximately 1,70 g/ml. If vanadium is present, the visual titration is applicable only to test portions containing less than 3 mg of vanadium. 4.5 Nitric acid, g approximately 1,40 g/ml. 2 References 4.6 Hydrochloric acid, g approximately 1,19 g/ml, diluted 1 + 1. Iso 377, Wrought steel --. Selection and preparation of samples and test pieces. 4.7 Hydrochloric acid, g approximately 1,19 g/ml, diluted Iso 385/1, Laboratory glassware -- Burettes - Part 1: General 1 + 10. requirements. Iso 648, Laboratory glassware -- One-mark pipettes. 4.8 Suifuric acid, g approximately 1,84 g/ml, difuted 1 + 1. ISo 1042, Laboratory glassware -- One-mark volumetric flasks. Determination of 4.9 Sulfuric acid, 0 approximately 1,84 g/ml, diluted 1 + 5. ISo 5725, Precision of test methods -- repeatability and reproducibility by inter-laboratory tests. 4.10 Sulfuric acid, Q approximately 1,84 g/ml, diluted 1 + 19. 3 Principle Dissolution of a test portion with appropriate acids. 4.11 Silver sulfate, 5 g/t solution. Oxidation of chromium in an acid medium to chromium(Vl) by 4.12 Ammonium peroxydisulfate [(NH4)2S2Ogl, 500 g/] ammonium peroxydisuifate in the presence of silver sulfate. Reduction of manganese(VIll) by hydrochloric acid. solution. Reduction of chromium(Vl) by ammonium iron(1) sulfate stan- Prepare this solution immediately before use. dard solution. 4.13 Manganese sulfate [MnsO4 H2O], 4 g/i solution. In the case of potentiometric detection, determination of the equivalence point by measurement of