7408 International Standard (ISO INTERNATIONAL ORGANIZATION FOR STANDARDIZATIONMEXAYHAPOAHAR OPFAHM3AUMS IO CTAHAAPTM3ALIWMORGANISATION INTE RNATIONALE DE NORMALISATION ANsI Internat Doc Sect Fertilizers - Determination of ammoniacal nitrogen content in the presence of other substances which release ammonia when treated with sodium hydroxide - Titrimetric method Engrais - Dosage de I'azote ammoniacal en présence'd'autres substances liberant de I'ammoniac sous I'effet d'hydroxyde de sodium -Methode titrimetrique First edition - 1983-12-15 ISO 7408-1983 (E) UDC 631.8 : 543.24 : 546.17 Ref.No. ISO 7408-1983 (E) Descriptors:fertilizers,chemicalanalysis,determination of content,nitrogen,ammoniacal nitrogen,volumetric analysis Price based on 5 pages Copyright ln Not for Resale Foreword iso (the International Organization for Standardization) is a worldwide federation of national standards bodies (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 authorized 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 themember bodies forapproval beforetheir acceptanceas International Standards by the Iso Council. International Standard ISO 7408 was developed by Technical Committee ISO/TC 134, Fertilizers and soil conditioners, and was circulated to the member bodies in July 1981. it has been approved by the member bodies of the following countries : Austria Israel Poland Brazil Italy Portugal China Kenya Romania Czechoslovakia Korea, Rep. of South Africa, Rep. of Egypt, Arab Rep. of Mexico Sri Lanka France Netherlands United Kingdom Germany, F.R. New Zealand USA Hungary Norway USSR The member body of the following country expressed disapproval of the document on technical grounds : India ? Internationai Organization for Standardization, 1983 Printed in Switzerland Copyright International Organization for Standardizatior No reproduction or networking permitted without license from IHS Not for Resale INTERNATIONAL STANDARD ISO7408-1983 (E) Fertilizers - Determination of ammoniacal nitrogen content in the presence of other substances which release ammonia when treated with sodium hydroxide - Titrimetric method 1 Scope and field of application 3.9 Mixed indicator solution: screened ethanolic methyl red solution. This International Standard specifies a method for the deter- minationof theammoniacal nitrogen contentoffertilizerscon- Mix 50 ml of a 2 g/l ethanolic methyl red solution with 50 ml of taining other substances, such as urea or urea-aldehyde con- a 1 g/l ethanolic methylene blue solution. densates, which release ammonia in the presence of sodium hydroxide. The colour of this indicator changes from lilac in acid medium, via grey at pH 5,4, to green in alkaline medium. 2 Principle 3.10 Ammonium sulfate, dried to constant mass at Entrainment,by means of a strong current of air,of the am- 100 °C. monia fromamoderatelyalkaline test mixtureat ambient temperature into standard volumetric sulfuric acid solution. 3.11 Urea. Back-titration of the excess sulfuric acid with standard volumetric sodium hydroxide solution. 4 Apparatus 3 Reagents Ordinary laboratory apparatus and During the analysis, use only reagents of recognized analytical grade, and only distilled water or water of equivalent purity. 4.1 Entrainment apparatus. 3.1 Nonyl alcohol (nonanol). The components of the apparatus may be connected by means of rubber bungs and tubing or by the use of ground glass joints. 3.2 Potassium carbonate, saturated solution at room temperature. Ground glass joints should be held by spring clamps to ensure that they are leak-tight. Rubber bungs and tubing should be 3.3 Sulfuric acid, approximately 590 g/l solution. re