ISO INTERNATIONAL STANDARD 2174 Third edition 1990-04-15 ANSl Internat Doc Seci Surface active agents - Preparation of water with known calcium hardness Agents de surface - Preparation d'une eau de durete calcique determinee Reference number ISO 2174 : 1990 (E) No reproduction or networking permited without license from IHS Not for Resale ISO 2174 : 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 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. IsO collaborates closely with the International Electrotechnical Commission (IEC) on all matters of electrotechnical standardization. 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 2174 was prepared by Technical Committee ISO/TC 91, Surface active agents. This third edition cancels and replaces the second edition (ISO 2174 : 1979), of which it constitutes a minor revision. Annex A of this International Standard is for information only. ISO 1990 Al 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 56 . CH-1211 Geneve 20 . Switzerland Printed in Switzerland yatingzaSandardiza with IS No reproduction or networking permitted without license from IHS Not fr Resale INTERNATIONAL STANDARD ISO2174:1990 (E) Surface active agents --- Preparation of water with known calcium hardness 1 Scope 3 Definition For the purposes of this International Standard, the following 1.1 This International Standard specifies a method of prepar- definition applies. ingwater ofknown calciumhardnessforuse intestingsurface active agents and products containing them. water hardness: The property resulting from the presence of calcium and magnesium salts and, in special cases, salts of 1.2Systematic investigations have shown that, in many tests strontiumand/orbarium onsurface active agentswithhardwater,there isno essential The unit of measurement of water hardness is the millimole per difference between calciumhardness andmagnesiumhard- ness, so that these tests can usually be carried out with an litre (mmol/l). 1 mmol/l of calcium hardness corresponds to aqueous solution of calcium chloride of knownhardness 40,08mgofcalciumionsperlitre The equivalents for other degrees of hardness of water, as well If, in certain cases, it is necessary to use other ions that give as other units used for measuring water hardness and the 'rise to the hardness of water, this fact shall be mentioned in the relationships between them, are given for information in test report. annex A. NOTE -- Originally, the hardness of a sample of water was determined by measuring its power to destroy the foam forrmed by soap. This pro- 2 Normative references perty is primarily due to the presence of calcium and magnesium, but salts of other metals, such as iron, aluminium and manganese, behave The following standards contain provisions which, through in a similar manner,although these seldom occur in natural waters. reference inthistext,constituteprovisions of thisInternational Standard.At the time of publication,the editions indicated Principle were valid.All standards are subject to revision,and parties to agreements based on this International Standard are encour- Preparation of a stock solution by dissolving an appropriate aged