981 NTERNATIONAL STANDARD ISO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION -MEKIYHAPO,IHA OPIAHH3ALIWA IIO CTAHIAPTH3AIIHM.ORGANISATION INTERNATIONALE DE NORMALISATION Sodium hydroxide for industrial use - Determination of chloride content - Mercurimetric method First edition - 1973-02-15 Avsl Internat Doc Sect UDC 661.322.1 : 546.132 : 543.24 Ref. No. ISO 981-1973 (E) ISO 981-1973 (E) Descriptors : sodium hydroxide, chemical analysis, determination of content, volumetric analysis, chlorides Price based on 2 pages Copyright International Organization for Standardization d without licensefrom IHS NotforResale 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 981 (originally Draft No. 2458) was drawn up by Technical Committee ISO/TC 47, Chemistry. It was approved in January 1972 by the Member Bodies of the following countries : india Portugal Austria Belgium Ireland South Africa, Rep. of Chile Israel Spain Czechoslovakia Italy Sweden Egypt, Arab Rep. of Korea, Dem. p. rep. of Switzerland Netherlands France Thailand Germany New Zealand United Kingdom Hungary Poland U.S.S.R. No Member Body expressed disapproval of the document. This International Standard cancels and replaces ISO Recommendation R 981-1969 Sodium hydroxide for industrial use -- Determination of chloride content - Volhard volumetricmethod. @ International Organization for Standardization, 1973 Printed in Switzerland Copyright International Organization for Standardization Notfor Resale INTERNATIONAL STANDARD ISO 981-1973 (E) Sodium hydroxide for industrial use - Determination of chloride content - Mercurimetric method 1 SCOPE acid solution (4.2), drop by drop, until the colour changes from blue to yellow. Add an excess of 3 drops of this acid This International Standard specifies a mercurimetric 0,5 to 1,0 mi of the diphenylcarbazone solution (4.8) and method for the determination of the chloride content of (from a burette) the volume of the standard voiumetric sodium hydroxide for industrial use. mercury(ll) nitrate solution (4.6) necessary to change the colour of the solution from yellow to mauve (2 drops). 2 FIELD OF APPLICATION 4.6 Mercury(ll) nitrate, 0,05 N standard volumetric sol- The method is applicable to products of which the sodium ution. chloride content is greater than 0,005 % (m/m). 4.6.1 Preparation of the solution NOTE - If 0,o2 N standard voiumetric mercury(1l) nitrate is used, the method is applicable to products of which the sodium chloride Weigh 5,43 ± 0,01 g of mercury(ll) oxide (HgO) and content is greater then 0,002 % (m/m). dissolve it in 10 ml of the nitric acid solution (4.1) in a 1 000 ml one-mark volumetric flask, dilute to the mark and 3 PRINCIPLE mix. Titration of the Cl" ion with mercury(ll) nitrate in the Standardize this solution following the procedure described in 4.6.2, adjusting it to the exact concentration, if presence of diphenylcarbazone as indicator. necessary. NOTE -- Analysts who can detect easily the diphenylcarbazone 4 REAGENTS colour change can take advantage of a O,o2 N standard volumetric solution (2,i8 g of Hg0 in 1 000 ml, standardized against a standard Distilled water or water of equivalent purity shall be used in reference solution of sodium chloride containing 1,168 8 g of NaCi in 1 000 ml) in order to increase the sensitivity of the method. the test. 4.1 Nitri