ISO INTERNATIONAL STANDARD 7393-3 Second edition 1990-06-01 Water quality - Determination of free chlorine and total chlorine Part 3: lodometric titration method for the determination of total chlorine Qualite de I'eau -- Dosage du chlore libre et du chlore total -- Partie 3: Methode par titrage iodometrique pour le dosage du chlore total Reference number ISO 7393-3 : 1990 (E) Copyright International Organization for Standardization No reproduction or networking permited without license from IHS Not for Resale ISO7393-3: 1990 (E) Foreword national standards bodies (ISO member bodies). The work of preparing International Standards is normally carried out through IsO technical committees. Each member the right to be represented on that committee. International organizations, govern- mental and non-governmental, in liaisonwithIsO,alsotakepart inthe work. Draft International Standards adopted bythe technical committees are circulated to the member bodies for approval before their acceptance as International Standards by least 75 % approval by the member bodies voting. International Standard ISO7393-3was prepared byTechnical CommitteeISO/TC 147, Water quality. This second edition cancels and replaces the first edition (IS0 7393-3 : 1986), of which it constitutes a minor revision. Iso 7393 consists of the following parts, under the general title Water quality -- Deter- mination of free chlorine and total chlorine: Part 1: Titrimetric method using N,N-diethyl-1,4-phenylenediamine Part 2:Colorimetric method usingN,N-diethyl-1,4-phenylenediamine for routine control purposes Part 3: fodometric titration method for the determination of total chlorine Annex A forms an integral part of this part of ISO 7393. Annexes B and C are for infor- mation only. ISO 1990 All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from the publisher International Organization for Standardization Case postale 56CH-1211 Geneve 20 . Switzerland Printed in Switzerland CopyrightIntematinal Organizationfor Standardizatin No reproductic permitted without license from IHS Not for Resale ISO 7393-3 : 1990 (E) INTERNATIONAL STANDARD Water quality - Determination of free chlorine and total chlorine Part 3: lodometric titration method for the determination of total chlorine 1 Scope 3.2 combined chlorine: The fraction of total chlorine present in the form of chloramines and organic chloramines. This part of 1SO 7393 specifies an iodometric titration method for the determination of total chlorine in water. 3.3 total chlorine: Chlorine present in the form of "free The method is applicable for the measurement of concen- chlorine"or"combined chlorine" or both. trations in terms of chlorine (Cl2) from 0,01 mmol/1 to 0,21 mmol/1 (0,71 mg/l to 15 mg/l). 3.4 chloramines: Derivatives of ammonia by substitution of one, two or three hydrogen atoms with chlorine atoms Several substances interfere in the determination (see (monochloramine NH,CI, dichloramine NHCl2, and nitrogen clause 10). trichloride NCl3) and all chlorinated derivatives of organic nitrogen compounds. In annex B a method for direct titration is specified. This is usually applied to the determination of chlorine concentrations above 7 μmol/l (0,5 mg/l) in treated drinking water. Table 1 -- Terms and synonyms in relation to actual compoundsinthesolution 2 Normative references Term Synonym Compounds Active free Eiemental chiorine, The following standards contain provisions which, through chlorine hypochlorous acid reference in this text, constitute provisions of this part of Free chlorine|Free chlorine Potential freel Hypochlorite 1So 7393. At the time of publication, the editions indicated chlorine were valid. All standards are subject to revision, and parties to agreements based on this part of 1so 7393 are encouraged to Elemental chlorine, investigate the possibility