INTERNATIONAL STANDARD (ISO) 3430 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION·MEKJYHAPOIHA OPIAHW3ALIM IO CTAHMAPTM3ALMW.ORGANISATION INTERNATIONALE DE NORMALISATION Sodium fluoride primarily used for the production of aluminium -- Determination of silica content - Reduced molybdosilicate spectrophotometric method Fluorure de sodium principalemenr utilise pour la production de I'aluminium -Dosage de la silice Methode spectrophotométrique au molybdosilicate reduit First edition - 1976-08-15 OCT 1 1 1976 ANSI Iniernat Doc Sect SO3430-19/6 (E) Ref. No. ISO 3430-1976 (E) UDC 661.833.316 : 546.284 : 543.42 Descriptors : chemical compounds, sodium ftuorides, chemical analysis, determination of content,silicon dioxide,spectrophotometric method. Price based on 5 pages from IHS JotforRes 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. Standard’ ISO 3430 was drawn up by Technical Committee International ISO/TC 47, Chemistry, and was circulated to the Member Bodies in February 1974. It has been approved by the Member Bodies of the following countries : Austria India Sweden Belgium Ireland Switzerland Bulgaria Israel Thailand Chile Italy Turkey Egypt, Arab Rep. of Poland United Kingdom Portugal France U.S.S.R. Germany Romania Yugoslavia Hungary South Africa, Rep. of No Member Body expressed disapproval of the document. @ International Organization for Standardization, 1976 Printed in Switzerland Copyright InternationalOrganization for Standardization e from IHS Not for Resale ISO 3430-1976 (E) INTERNATIONAL STANDARD Sodium fluoride primarily used for the production of aluminium --- Determination of silica content - Reduced molybdosilicate spectrophotometric method 4.3 Nitric acid, approximately 8 N solution. 1 SCOPEANDFIELDOFAPPLICATION Ditute 540 ml of nitric acid solution, p approximately This International Standard specifies a spectrophotometric 1,40 g/mi, about 68 % (m/m) solution, with water to method, using the reduced molybdosilicate. for deter mining the silica content of sodium fluoride primarily 1 000 ml and mix. used for the production of aluminium. 4.4 Sodium molybdate, 195 g/l (0,8 M approximately) The method is applicable to products of which the P,Os solution. content docs not exceed 0,02 % (m/m) Dissolve, in a beaker made of material free from silica, 19,5 g of sodium molybdate dihydrate (Na2Mo04.2H,0) 2 REFERENCE ISO3428,Sodiumfluorideforindustrial use--Preparation Transfer the solution to a bottle made of material free from and storage of test samples. silica and, if necessary, filter before use. 4.5 Tartaric acid, 100 g/l solution. 3 PRINCIPLE Dissolve 10 g of tartaric acid in water, dilute to 100 ml and Aikaline fusion of a test portion by means of a mixture mix. of sodium carbonate and boric acid. Solution of the fused mass in excess nitric acid so that the pH oi the Store the solution in a bottle made of material free from final solution is between 0,3 and 0,5 after being diluted silica. to 250 ml. Formation, in a suitable aliquot portion, of the oxidized 4.6 Sulphuric acid, approximately 16 N solution. molybdosilicate(yellow).under well-defined conditions Carefully add 450 ml of sulphuric acid, p approximately of acidity, 'concentration of reagents, temperature and 1,84 g/ml, about 96 % (m/m) solution, to about 500 ml time. of water. Cool, dilute to 1 000 mi and mix. Selective reduction of