ISO 1693 NTERNATIONAL STANDARD INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEKIYHAPOIHA OPIAHW3ALIM JIO CTAHIAPTW3ALIW.ORGANISATION INTERNATIONALE DE NORMALISATION Cryolite, natural and artificial - Determination of fluorine content - Modified Willard-Winter method Cryolithe, naturelle et artificielle - Dosage du fluor - Meéthode de Willard-Winter modifiee First edition -. 1976-09-15 1341070 ISO 1693-1976 (E) Ref. No. 1SO 1693-1976 (E) UDC 553.634:546.16:543.24 Descriptors : aluminium ores, cryolite, chemical analysis, determination of content, fluorine. Price based on 6 pages Copyright International Organization for Standardization Notfor 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, aiso take part in the work. Draft International Standards adopted by the Technicat Committees are circulated to the Member Bodies for approval before their acceptance as International Standards by the ISO Council. Prior to 1972, the results of the work of the Technical Committees were published as iso Recommendations; these documents are now in the process of being transformed into Internationa! Standards. As part of this process, Technical Committee ISO/TC 47 has reviewed ISO Recommendation R 1693 and found it technically suitable for transformation. nternational Standard ISO 1693 therefore replaces IS0 Recommendation R 1693-1970 to which it is technically identical. ISO Recommendation R 1693 was approved by the Member Bodies of the following countries : Hungary Australia Romania India Austria South Africa, Rep. of Belgium Iran Spain Brazil Israel Switzerland Canada Italy Thailand Czechoslovakia Netherlands Turkey Egypt, Arab Rep. of New Zealand United Kingdom Norway U.S.S.R. France Germany Peru Yugoslavia Poland Greece No Member Body expressed disapproval of the Recommendation. No Member Body disapproved the transformation of iSO/R 1693 into an International Standard. @ International Organization for Standardization, 1976 Printed in Switzerland Copyright International Organization for Standardization e from IHS Not for Resale ISO 1693-1976 (E) INTERNATIONAL STANDARD Cryolite, natural and artificial -- Determination of fluorine content -- Modified Willard-Winter method 1 SCOPE AND FIELD OF APPLICATION 4.4 Sulphuric acid, approximately 24 N solution. Carefully add, in small quantities, 200 mi of suiphuric acid This International Standard specifies a modified Willard- p approximately 1,84 g/ml, about 96 % (m/m) solution, to Winter method for the determination of the fluorine approximately 100 ml of water, cool and dilute to 300 ml. content of natural and artificial cryolite and of natural and synthetic materials having a molar ratio (NaF/AIF3) or between 3 and 1,7 approximately 4.4.1 Perchloric acid, p approximately 1,60 g/ml, about 64,5 % (m/m) solution. 2 REFERENCE 4.5 Buffer solution, of pH 2,7. iso 1619, Cryolite, natural and artificial - Preparation and storage of test samples. Dissolve 9,45 g of monochloroacetic acid in 50 ml of 1 N sodium hydroxide solution and dilute to 100 ml. 3 PRINCIPLE 4.6 Thorium nitrate, approximately 0,067 N standard volumetric solution. Fusion of a test portion with sodium carbonate. 1 mi of this standard volumetric solution is equivalent to approximately 1,3 mg of fluorine (F). Separation of fluorine by distillation with sulphuric acid or perchioric acid. Titration with thorium nitrate solution using sodium alizarinsulphonate-methylene blue as 4.6.1 Preparation of the solution indicator. Alternatively, the thorium nitrate titration may be made Dissolve 9.45 g of thorium nitrate tetrahydrat