6437 International Standard (ISO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEXAYHAPOAHAR OPIAHM3AUMA HO CTAHAAPTM3AWW+ORGANISATION INTERNATIONALE DE NORMALISATION Copper alloys --- Determination of chromium content Titrimetric method Alliages de cuivre--Dosagedu chrome-Methode titrimetrique First edition - 1984-05-15 ISO 6437-1984 (E) UDC669.35:543.24:546.76 Ref.No.ISO6437-1984(E) Descriptors : copper, copper alloys, chemical analysis, determination of content, chromium, volumetric analysis. Price based on 3 pages Standardizatiol No reproduction or networking permitted without license from IHS Not for Resale Foreword ISo (the International Organization for Standardization) is a worldwide federation of national standards bodies (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 authorized has the 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 IsoCouncil. International Standard ISO 6437 was developed by Technical Committee ISO/TC 26, Copper and copper alloys, and was circulated to the member bodies in April 1982. It has been approved by the member bodies of the foliowing countries: Australia France Poland Belgium Germany, F.R. Romania Brazil Hungary South Africa, Rep. of Canada Iran Spain Czechoslovakia Italy Sweden China Japan Switzerland Egypt, Arab Rep. of Netherlands Turkey Finiand Norway USSR The member body of the following country expressed disapproval of the document on technical grounds: USA InternationalOrganizationforStandardization,1984 Printed in Switzerland No reproduction or networking permitted without license from IHS Not for Resale ISO6437-1984 (E) INTERNATIONAL STANDARD Copper alloys --. Determination of chromium content Titrimetric method WARNiNG --. Throughout this International Standard, normal precautions regarding the use of perchloric acid in laboratory work shall be observed. Scope and field of application 3.5 Sulfuric acid, Q 1,83 g/ml. This International Standard specifies a titrimetric method for 3.6 Hydrochloric acid, solution, 1 + 20. the determination of the total chromium content of copper- chromium alloys listed in International Standards. Dilute 5,0 ml of the hydrochloric acid (3.1) with 100 ml of water. The method is applicable to products having chromium con- tents between 0,10 and 2,0 % (m/m). 3.7 Orthophosphoric acid, solution , 1 + 2. Dilute 100 ml of orthophosphoric acid, g 1,70 g/ml, with 200 ml 2 Principle of water. Dissolution of a test portion foliowed by oxidation of the buik 3.8 Potassium permanganate, 2,5 g/l solution. of chromium byperchloricacid in the presenceof.or- thophosphoric acid to avoid loss of chromium. Oxidation of Dissolve 2,5 g of potassium permanganate in water and dilute residual chromium(lil)bypotassiumpermanganate.Reduction to 1 000 ml. of chromium(Vi)by iron(ll)solution,and determination of the equivalencepointeitherusing an indicator orbymeasuringthe 3.9 Diphenylamine, 2 g/l in sulfuric acid. change in potential as a function of the volume of titrant used. Dissolve 0,2 g of diphenylamine in 100 ml of suifuric acid (3.5). 3Reagents 3.10 Potassium dichromate, standard solution cor- During the analysis, use only reagents of recognized analytical responding to 1,733 g of Cr per litre. grade, and only distlled water or water of equivalent purity. Weigh, to the nearest 0,000 1 g, 4,903 3 g of potassium 3.1 Hydrochloric acid, @ 1,19 g/ml. dichromate (K2Cr20)). 3.2 Nitric acid, 1,40 g/ml. Place in a beaker of suitable capacity and dissolve in reductant- free water. Transfer quantitatively to a 1 000 ml one-mark volumetric flask, dilute to the mark with reductant-free water 3.3 Hydrofluoric acid, @ 1,13 g/ml. and mix. 3.4