NTERNATIONAL STANDARD (SO 3423 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION·MEKIYHAPOIHA OPFAHM3ALIM HO CTAHIAPTH3ALIWH.ORGANISATION INTERNATIONALE DE NORMALISATION Sulphuric acid and oleums for industrial use --- Determination of sulphur dioxide content - lodometric method Acide sulfurique et oleums a usage industriel -- Dosage du dioxyde de soufre -- Methode iodométrique First edition - 1975-11-01 ANsl Internat Doc Sect NOV 3-1975 UDC 661.25 : 546.224 : 543.242.3 Ref. No. ISO 3423-1975 (E) Descriptors : sulphuric acid, chemical analysis, determination of content, sulphur dioxide, volumetric analysis. Price based on 3 pages nsefromIHS Not for Resale 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. Internationat Standard ISO 3423 was drawn up by Technical Committee ISO/TC 47, Chemistry, and circulated to the Member Bodies in February 1974. It has been approved by the Member Bodies of the following countries : Austria South Africa, Rep. of India Belgium Israel Switzerland Bulgaria Italy Thailand Chile Netherlands Turkey New Zealand Egypt, Arab Rep. of United Kingdom Poland U.S.S.R. France Portugal Germany Yugoslavia Hungary Romania No Member Body expressed disapproval of the document. @ International Organization for Standardization, 1975 PrintedinSwitzertand Copyright International Organization for Standardization Notfor Resale INTERNATIONAL STANDARD ISO 3423-1975 (E) Sulphuric acid and oleums for industrial use -- Determination of sulphur dioxide content - Iodometric method 1 SCOPE AND FIELD OF APPLICATION 4 APPARATUS This International Standard specifies an iodometric method Ordinary laboratory apparatus and for the determination of the sulphur dioxide content of sulphuric acid and oleums for industrial use. The method is 4.1 Glass apparatus, with ground joints, comprising (see applicable to products of which the sulphur dioxide example in figure) : content is equal to or greater than 2 mg/kg. A : 3-necked flask, 500 ml or 250 ml capacity; NOTE - - For sulphur dioxide contents higher than 50 mg/kg, see also ISO/R 912. B : cylindrical dropping funnel, fitting into one of the two side necks of the flask; C : tube, fitted with a stopcock, fitting into the central neck of the flask and terminating in a fritted disc at a 2 PRINCIPLE level of about 1 cm above the bottom of the flask. Displacement of the suiphur dioxide present in a test D1, D2, D3 : three gas-washing bottles, Drechsel type, portion by a current of pure nitrogen and absorption in a 100 or 125 ml capacity, with the inlet tubes terminating known volume of iodine solution. in fritted discs (porosity P16 (pore diameter 4 to Titration of the excess of iodine with standard volumetric 16 μm)) to disperse the gas. sodium thiosulphate solution. 4.2 Glass flask with ground glass stopper. 4.3 Flowmeter or bubble-counter. 3 REAGENTS During the analysis, use only reagents of recognized analytical reagent grade, and only distilled water or water 5 PROCEDURE of equivalent purity. 3.1 Hydrazinium sulphate. 5.1 Test portion 3.2 lodine, approximately 0,1 N, 0,05 N or 0,01 N and take, weighing by difference to the nearest 0,05 g, a solution, as required (see 5.3). test portion of approximately 200 g. Prepare this solution at the time of use. If the sample is of acid with a density higher than about 1,70 g/ml or is of oleum, stowly pour the test portion, 3.3 So