92-02E 4851903 00274746 NTERNATIONAL STANDARD (ISO 3704 G--7L INTERNATIONAL ORGANIZATION FOR STANDARDIZATION-MEXKAYHAPOAHAR OPTAHH3ALWA IIO CTAHIAPTH3ALIWH.ORGANISATION INTERNATIONALE DE NORMALISATION Sulphur for industrial use - Determination of acidity -- Titrimetric method Soufre a usage industriel-Détermination de I'acidite -Methode titrimetrique First edition--1976-09-01 1SO 3704-1976 (E) UDC661.21:543.257.1 Ref.No.ISO3704-1976 (E) Descriptors : chemical compounds, sulphur, chemical analysis,determination, acidity,volumetric analysis. Price based on 2 pages COPYRIGHT 2000 International ization For Standa ation Information Handling Services, 2000 4851903 0027475 8 3704-76 FOREWORD Iso (the International Organization for Standardization)is a worldwidefederation 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 StandardsbytheIso Council. International Standard isO 3704 was drawn up by Technical Committee ISo/TC 47, Chemistry, and was circulated to the Member Bodies in January 1975. It has been approved by the MemberBodies of the following countries : Austria India Spain Belgium Ireland Switzerland Brazil Israel Turkey Bulgaria Poland United Kingdom Czechoslovakia Portugal U.S.S.R. France Romania Yugoslavia Germany South Africa, Rep. of No Member Body expressed disapproval of the document. @InternationalOrganizationforStandardization,1976 Printed in Switzerland COPYRIGHT 2ooo International Organization For Standardization Information Handling Services, 2000 INTERNATIONAL STANDARD ISO3704-1976 (E) 3704-76 EObTSRh 0 Sulphur for industrial use - Determination of acidity Titrimetric method 1 SCOPEANDFIELDOFAPPLICATION Prepare a test sample from the laboratory sample by grinding a sufficient quantity of the undried sample until This International Standard specifies a titrimetric method it passes through a sieve of nominal aperture 250 μm. for the determination of the acidity of suiphur for industrial use. The method is applicable to products having acidities, 6PROCEDURE expressed as H2s04, equal to or greater than 0,01 % (m/m). 6.1 Testportion Weigh, to the nearest 0,1 g, about 25 g of the test sample 2 PRINCIPLE (clause 5) in a 250 ml conical flask fitted with a ground Extraction of acidic substances with a mixture of water glass stopper. and propan-2-ol. Titration of the extract with standard volumetric sodium hydroxide solution in the presence of 6.2Determination phenolphthalein as indicator. To the conical flask containing the test portion (6.1), add 25 ml of the propan-2-ol (3.1), stopper the flask and shake until the suiphur is completely wetted. Then add 50 ml of 3REAGENTS water, stopper the flask, and shake again for 2 min. Allow to stand for 20 min,shakingoccasionally. During the analysis, use only reagents of recognized analytical grade and only distilled water,freshly boiled Titrate with the standard volumetric sodium hydroxide and cooled, or water of equivalent purity. solution (3.2), in.the presence of a few drops of the phenolphthalein solution (3.3), to the first permanent 3.1 Propan-2-ol, previously boiled, cooled, and neutralized pink colour. in the presence of the phenolphthalein solution (3.3). 7EXPRESSIONOFRESULTS 3.2Sodium hydroxide, 0,1 Nstandard volumetric The acidity, expressed as a percentage by mass of sulphuric solution, freshly prepared and carbonate-free. acid (H2SO4), is given by the formula 3.3Phenolphthalein,10 g/lethanolic solution. 1 100 _0,49×V Vx ×0,049× 10 m m Dissolve 1g of phenolphthalein in 6