NTERNATIONAL STANDARD (tso) 3909 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEXIYHAPOIHA OPIAHW3ALIN HO CTAHAAPTH3AIMW·ORGANISATION INTERNATIONALE DE NORMALISATION Hardmetals -- Determination of cobalt -- Potentiometric method Metauxdurs--Determinationducobalt-Methodepotentiométrique First edition - 1976-10-15 UDC 621.762 : 546.73 : 543.257.1 Ref. No. ISO 3909-1976 (E) ISO 3909-1976 Descriptors:powder metallurgy， sinteredproducts, hardmetals, carbides, chemicalanalysis,determinationofcontent,cobalt, potentiometric analysis. Price based on 3 pages No reproduction or networking permited without license from IHS Not for Resale FOREWORD iso (the International Organization for Standardization) is a worldwide federation of national standards institutes (isO Member Bodies). The work of developing International Standards is carried out through ISO Technical Committees. Every Member Body interested in a subject for which a Technical Committee has been set up has the right to be represented on that Committee. International organizations, governmental 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 approvai before their acceptance as International Standards by the ISO Council. International Standard ISO 3909 was drawn up by Technical Committee Iso/Tc 119,Powder metallurgical materials and products, and was circulated to the Member Bodies in July 1975. It has been approved by the Member Bodies of the foilowing countries : Austria Morocco Turkey Czechoslovakia Poland United Kingdom France Romania U.S.A. Germany South Africa, Rep. of U.S.S.R. Ireland Spain Italy Sweden The Member Bodies of the following countries expressed disapproval of the document on technical grounds : Australia Canada International Organization for Standardization, 1976 : Printed in Switzerland Copyright Intermational Organization for Standardization No reproduction or networking permited without license from IHS Not for Resale -ISO 3909-1976 (E) INTERNATIONAL STANDARD Hardmetals -- Determination of cobalt - Potentiometric method 1SCOPE 5.3 Hydrofluoric acid, p 1,12 g/ml. This. International Standard specifies a potentiometric 5.4 Nitric acid, p 1,42 g/ml. method for the determination of the cobalt content of hardmetals. 5.5 Sulphuric acid, p 1,84 g/ml. 2 FIELDOF APPLICATION 5.6 Ammonia solution, p 0,91 g/ml. This method is applicable to 5.7 Ammonium citrate solution. carbides and binder metal powder mixtures, free Dissolve 100 g of citric acid in 900 ml of water and add of lubricant, 100 ml of the ammonia solution (5.6) all grades of presintered or sintered hardmetals, 5.8 Cobalt sulphate, standard reference solution contain- having a cobalt content exceeding 1 % (m/m). ing 3 g of cobalt per litre. Prepare the solution from compact metallic cobalt, or 3 PRINCIPLE from diammonium cobalt sulphate, or from cobalt sui- phate. If necessary, establish the titre gravimetrically with Oxidation of cobalt to the trivalent state in a strongly 1-nitroso-naphthol-2, or electrolytically. ammoniacal solution with an excess of potassium hexa- cyanoferrate(lll). Potentiometric back-titration of the 5.9 Potassium hexacyanoferrate(ll), standard volumetric excess with cobalt sulphate solution. solution. 1 I should correspond to approximately 3 g of cobalt. 4 INTERFERING ELEMENTS Dissolve 17 g of K3[Fe(CN)6] in 1 1 of water. The effect of interfering elements, for example vanadium Determine the relationship between the volumes of the and manganese, shall be taken into account. Vanadium and cobalt sulphate solution (5.8) and the potassium hexa- manganese are also oxidized by hexacyanoferrate(lll). cyanoferrate(11l) solution (5.9) in the following way. Vanadium reacts stoichiometrically and a correction can be applied if the vanadium content is below 0,5 % (m/m). 5.9.1 Transfer into a 400 ml beaker 5 g of the ammonium Manganese reacts almost stoichiometrical