4281 NTERNATIONAL STANDARD TSO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEXKIyHAPOHA OPrAHW3AlIWS HO CTAHIAPTH3AIWH.ORGANISATION INTERNATIONALE DE NORMALISATION Sodium hexafluorosilicate for industrial use -- Determination of free acidity and total hexafluorosilicate content Titrimetric method Hexafluorosilicate de sodium a usage industriel -- Determinations de I'acidite libre et de la teneur enhexafluorosilicatetotal--Methodetitrimetrique First edition - 1977-03-01 FEB 2 3 1917 ANsl Internat Doc Sec! ISO 4281-1977 (E) Ref. No. 1SO 4281-1977 (E) UDC 661.833 : 543.241.5 Descriptors : chemical compounds, sodium fluorsilicate, chemical analysis, determination of content, acidity, sodium fluorsilicate, volu metricanalysis. Price based on 2 page 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. International Standard ISO 4281 was developed by Technical Committee iSO/TC 47, Chemistry, and was circulated to the member bodies in August 1975. It has been approved by the member bodies of the following countries : Belgium India Spain Brazil Israel Switzerland Turkey Czechoslovakia Italy Egypt, Arab Rep. of Mexico United Kingdom Poland France U.S.S.R. Germany Romania Hungary South Africa, Rep. of No member body expressed disapproval of the document. @ Internationat Organization for Standardization, 1977 Printed in Switzerland Copyright International Organization for Standardization from IHS Not for Resale ISO 4281-1977 (E) INTERNATIONAL STANDARD Sodium hexafluorosilicate for industrial use -- Determination of free acidity and total hexafluorosilicate content - Titrimetric method WARNING - Sodium hexafluorosilicate is poisonous if taken internally. Breathing of the dust should be avoided. Contact with the eyes and skin should be prevented and operators shouid wash thoroughiy after handling the material and should wear a respirator and goggies when handling the powdered material. 1 SCOPE AND FIELD OF APPLICATION 4 REACTIONS This International Standard specifies a titrimetric method Cold titration for the determination of the free acidity and the total H2SiF。 + 2NaOH → Na2SiF。 + 2H20 hexafluorosilicate content of sodium hexafluorosilicate Hot titration to products having free acidities, expressed as a percentage by mass of hexafluorosilicic acid (H2SiF6), equal to or Na2 SiF。 + 4NaOH →6NaF + SiO2 + 2H20 greater than 0,1. 5 APPARATUS 2 PRINCIPLE Ordinary laboratory apparatus. Determination of the free acidity by titration of an ice-cold test portion with a standard volumetric sodium hydroxide 6 PROCEDURE solution in the presence of potassium nitrate and using bromothymol blue as indicator, followed by titration at 6.1 Test portion near boiling temperature to determine the total hexafluoro- In a glass weighing bottle, weigh, to the nearest 0,001 g, silicate content. between 1,00 and 1,20 g of the test sample. 6.2 Determinations 3 REAGENTS Transfer the test portion (6.1) quantitatively to a 500 ml During the analysis, use only reagents of analytical grade beaker containing about 100 g of the crushed ice (3.1) and only distilled water or water of equivalent purity. and 25 ml of the potassium nitrate solution (3.2), rinsing the residue from the weighing bottle into the beaker with 3.1 Crushed ice, prepared from distilled water or water of the minimum quantity of water. Wash down the sides of equivalent p