(ISO 7497 International Standard INTERNATIONAL ORGANIZATION FOR STANDARDIZATION MEXAYHAPOAHAR OPIAHM3AUMA HO CTAHAAPTW3AUNMORGANISATION INTERNATIONALE DE NORMALISATION Fertilizers - Extraction of phosphates soluble in mineral acids Engrais-Extractiondesphosphatessolublesdanslesacidesminéraux First edition 1984-11-01 UDC 631.8 : 543.722 : 546.185 Ref. No. . ISO 7497-1984 (E) ISO 7497-1984 (E) Descriptors : fertilizers, tests, extraction, soluble matter, orthophosphates. Price based on 2 pages Copyright International Organization for Standardization Not forResale Foreword ISO (the International Organization for Standardization) is a worldwide federation of national standards bodies (Iso member bodies). The work of preparing International Standards is normally carried out through IsO technical committees. Each member body interested in a subject for which a technical committee has been established has the right to be represented on that committee. International organizations, govern- mental 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 least 75 % approval by the member bodies voting. International Standard ISO 7497 was prepared by Technical Committee ISO/TC 134, Fertilizers and soil conditioners. @ International Organization for Standardization, 1984 Printed in Switzerland Copyright International Organization for Standardization efrom IHS Not for Resale ISO 7497-1984 (E) INTERNATIONAL STANDARD Fertilizers -- Extraction of phosphates soluble in mineral acids 0 Introduction 2.4 Test sample Grind the laboratory sample until it passes through a sieve of The two methods specified in this International Standard have aperture size 0,5 mm. been recognized as equivalent for the extraction of mineral acid-soluble phosphates. 2.5 Procedure Scope and field of application 1 2.5.1 Test portion Weigh, to the nearest 1 mg, 2,5 g of the test sample and This International Standard specifies a method for the extrac- tion of mineral acid-soluble phosphates by attack with a mix- transfer it to a 400 ml beaker. ture of hydrochloric and nitric acids and a method by attack with a mixture of sulfuric and nitric acids. 2.5.2 Extraction Add 50 ml of the acid mixture (2.2). Cover the beaker with a These methods are applicable to all phosphate fertilizers and to mineral phosphates containing low amounts of organic matter. clock-glass. Bring the mixture to boiling and simmer for 30 min. Add 100 ml of water, bring to boiling and simmer for a further 15 min. Cool to room temperature. 2 Method A: Hydrochloric acid/nitric acid Transfer to the one-mark volumetric flask (2.3.2) and dilute to attack the mark with water. Mix carefully and filter the solution through a dry, folded medium-grade filter paper, free from 2.1 Principle phosphates. Discard the first two approximately 30 ml por- tions. Dissolution of the phosphates present in fertilizers or in mineral NOTE - The filtrate should be clear. phosphates in a mixture of hydrochloric and nitric acids. 2.2 Reagents 3 Method B: Sulfuric acid/nitric acid attack Aill reagents shall be of recognized analytical grade, and the 3.1 Principle water used shall be distilled water or demineralized water of Dissolution of the phosphates present in fertilizers or in mineral equivalent purity. phosphates in a mixture of sulfuric and nitric acids Acid mixture. 3.2 Reagents Add 3 volumes of nitric acid (020 = 1,40 g/ml) to 1 volume of All reagents shall be of recognized analytical grade, and the hydrochioric acid (020 = 1,19 g/ml). Mix well, dilute with four water used shall be distilled water or demineralized water of volumes of water and mix again. equivalent purity. Use a freshly prepared acid mixture. 3.2.1 Sulfuric acid (020 = 1,84 g/ml). 2.3 Apparatus 3.2.2 Nitric acid (α20 = 1,40 g/ml). Ordinary laboratory apparatus, and in particul