2997 NTERNATIONAL STANDARD .TSO Phosphoric acid for industrial use -- Determination of sulphate content - Method by reduction and titrimetry Acide phosphorique a usage industriel - Dosage des sulfates - Méthode par reduction et titrimétrie First edition - 1974-11-01 0CT 3 1 1974 ANSI Internat Doc rt UDC 661.634:546.226 : 543.242 Ref. No. ISO 2997-1974 (E) Descriptors:phosphoric acids,chemical analysis,determination of content,sulphates,voiumetric analysis. Price based on 3 pages ght International Organization for Standardizatioi Not for Resal 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 liaisonwithIsO,alsotake part inthe 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 IsO2997 was drawn up by Technical Committee ISO/TC 47, Chemistry, and circulated to the Member Bodies in December 1972. It has been approved by the Member Bodies of the following countries : Australia India Spain Belgium Israel Sweden Brazil Italy Switzerland Czechoslovakia Netherlands Thailand France NewZealand Turkey Germany Poland United Kingdom Hungary South Africa, Rep. of Yugoslavia This International Standard has also been approved by the International Union of PureandAppliedChemistry(IUPAC). The Member Bodies of the following countries expressed disapproval of the document ontechnical grounds: Austria Bulgaria InternationalOrganizationforStandardization,1974 Printed'in Switzerland forStandardization No reproduction or networking pemitted without license from IHS Not for Resale ISO 2997-1974 (E) INTERNATIONAL STANDARD Phosphoric acid for industrial use - Determination of sulphate content -- Method by reduction and titrimetry 1 SCOPEANDFIELDOFAPPLICATION 3.5Sodiumsulphate,0,001Mstandardreferencesolution. This international Standard specifies a method, by Weigh, to the nearest 0,000 1 g, 0,142 0 g of anhydrous reduction and titrimetry, for the determination of the sodium sulphate, previously dried at 110 °c and cooled in a sulphate content of phosphoric (orthophosphoric) acid for desiccator.Introduce into a 1O00 ml one-mark volumetric industrial use and is applicable to sulphate contents, flask, dissolve in water, dilute to the mark and mix. expressed as s04, equal to or greater than 0,000 5% 1 m! of this solution corresponds to 96 μg of SO4. (m/m). 3.6 Mercury(il) acetate, 0,001 M standard volumetric solution. 2 PRINCIPLE Weigh, to the nearest 0,000 1 g, 0,318 7 g of mercury(11) Reduction of the sulphate to sulphide by a mixture of acetate [Hg(CH3COO)2]. Introduce into a 1000 m! hydriodic acid and hypophosphorous acid. one-mark volumetric flask, dissolve in water, dilute to the Absorption of the hydrogen sulphide evolved in a mixture mark and mix. of acetone and sodium hydroxide solution. Titration with a Alternatively, 0,001 M standard volumetric mercury(ll) standard volumetric solution of mercury(ll) acetate in the nitrate solution may be used. presence of dithizone as indicator. 3.6.1 Mercury(l1) nitrate, 0,001 M standard volumetric solution. 3 REAGENTS Weigh 10,85 ± 0,01 g of mercury(ll) oxide (Hg0), place in During the analysis, use only reagents of recognized a beaker of suitable capacity (for example 100 ml) and analytical reagent grade, and only distilled water or water dissolve in 10 m! of nitric acid solution, p approximately of equivalent purity. 1,40 g/ml, about 68 % (m/m) solution. Dilute the solution, transfer it quantitatively to a 1 000 ml 3.1 Hydriodic acid, p approximately 1,71 g