4311 (iSo International Standard ANst Intgruct Doc.sar Anionic and non-ionic surface active agents Determination of the critical micellization concentration - Method by measuring surface tension with a plate, stirrup or ring Agents de surface anioniques et non ioniques --. Determination de la concentration critique pour la formation de micelles -- Methode par mesurage de la tension superficielle a la lame, a I'étrier ou a I'anneau First edition --- 1979-06-01 JUN 0 8. UDC 661.185 : 532.6 Ref. No. ISO 4311-1979 (E) Descriptors : surfactants, determination of content, critical concentration, anionic-active matter, non-ionic active matter, distilled water, tests physical tests, interfacial tension, measurement. Price based on 3 pages Copyright International Organization for Standardization 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 approval before their acceptance as International Standards by the Iso Council. International Standard iSO 4311 was developed by Technical Committee ISO/TC 91, Surface active agents, and was circulated to the member bodies in October 1975. It has been approved by the member bodies of the following countries : Iran Portugal Austria Belgium Italy Romania Brazil South Africa, Rep. of Japan Canada Korea, Rep. of Spain Mexico France Switzerland Germany, F. R. Netherlands Turkey Hungary New Zealand USA India Poland USSR The member body of the following country expressed disapproval of the document on technical grounds : United Kingdom @ International Organization for Standardization,1979 Printed inSwitzerland Copyright International Organization for Standardization from IHS Not for Resale ISO 4311-1979 (E) INTERNATIONAL STANDARD Anionic and non-ionic surface active agents Determination of the critical micellization concentration -- Method by measuring surface tension with a plate, stirrup or ring 0 INTRODUCTION active agents which are soluble in water and have a Krafft temperature at least 5 'c beiow the testing temperature. Curves showing the variation in the physical properties of aqueous solutions of surface active agents are specifical This method may be used for measurements at temperatures to individual products; in a certain region of concentration, above 35 'c, but very strict precautions shall then be taken usually very narrow, these curves show a sharp change of to prevent water and other possible solvents from evaporat- slope. This phenomenon has been attributed to the ing. formation of orientated aggregates of molecules, and the concentration at which this change occurs has been termed the "critical micellization concentration" (c.m.c.)1) 3 REFERENCES For a given length of hydrophobic chain, the critical Is0 304, Surface active agents - Determination of surface micellization concentration is usually higher in the case of tension. ionic surface active agents than in the case of non-ionic Is0 607, Surface active agents and detergents - Methods of surface active agents. Apart from the structure of the sample division.2) surface active agent, the temperature, and the presence, the nature and the quantity of the metallic salts, organic ISO/R 862, Surface active agents - Glossary. compounds cause the critical micellization concentration to IsO 2456, Surface active agents - Water used as a solvent vary, and hence the operational conditions likely to for tests. 3) influence the result must be clearly stated, i.e. the purity of the product and, as far as p