ISO INTERNATIONAL STANDARD 9101 First edition 1987-12-15 INTERNATIONALORGANIZATIONFORSTANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATION MEXKAYHAPOAHAAOPIAHM3ALMANOCTAHAAPTW3AWM Surface active agents - Determination of interfacial tension - Drop volume method Agents de surface - Determination de la tension interfaciale - Methode au volume degoutte Referencenumber ISO9101:1987(E) Copyright International Organization for Standardizatior 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 normallycarried outthroughIsOtechnical committees.Eachmember 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 9101 was prepared by Technical Committee ISO/TC 91, Surface active agents. 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. ? InternationalOrganizationforStandardization,1987 Printed in Switzerland yright Intemational Organization for Standardization Provided by IHS under license with ISO No reproduction or networking permited without license from IHS Not for Resale INTERNATIONALSTANDARD ISO9101:1987 (E) Surface active agents - Determination of interfacial tension - Drop volume method O Introduction 3 Definition Interfacial tension is a fundamental property of the interface interfacial tension:SeeISO862. between two immiscible or partially miscible liquids. These two liquids may contain surface active agents which reduce the in- NOTE -- The SI unit of interfacial tension is the newton per metre terfacial tension, but it is generally not possible to predict their (N/m). In practice, the sub-multiple millinewton per metre (mN/m).is detergentand emulsifying activities frommeasurements of the used. interfacial tensionalone. 4 Principle Scope and field of application This International Standard specifies a test method, by measur- Measurement of the volume of a drop of an aqueous phase formed at the end of a vertical capillary tube when it detaches ing the drop volume,for the determination of the interfacial from the tube in contact with the organic phase. tension between two liquid phases. It is particularly suitable for the measurement of the interfacial Obtaining the interfacial tension between two liquid phases by balancing the weight of the drop with the interfacial tension tension between two solutions of surface active agents in aqueous or organic solvents, and provides some advantages force supporting it and applying a correction factor; then compared with the method by drawing up liquid films calculation of the interfaciai tension from the volume of the (ISo 6889), which are the following : falling drop, the outer capillary radius, the density difference between the two liquid phases and the acceleration due to determination of interfacial tension between two liquid gravity. phases containing all types of surface active agents, including cationic surface active agents; 5 Apparatus accurate measurement of low interfacial tensions of the order of 1 mN/m; 5.1 Measuring instrument (see figure 1) comprising the following elements. repeatability standard deviation less than ± 0,5 mN/m (acceptablefor control in industrial laboratories); 5.1.1 Glass syringe, accurately calibrated, of 0,5 cm3 determination of interfacial ten