5315 International Standard (TSO INTERNATIONAL ORGANIZATION FOR STANDARDIZATION+MEXAYHAPOAHAH OPIAHM3ALWA HO CTAHAAPTW3ALWWORGANISATION INTERNATIONALE DE NORMALISATION ANsi lmtexmat Doc Sect Fertilizers Determination of total nitrogen content .- Titrimetric method after distillation Engrais -- Dosage de I'azote total - Methode titrimetrique apres distillation First edition - 1984-06-01 UDC 631.8 : 543.24 : 546.17 Ref. No. ISO 5315-1984 (E) ISO 5315-1984 (E) Descriptors: fertilizers, chemical analysis, determination n of content,nitrogen,volumetricanalysis,distillation Price based on 5 pages Copyright International Organization for Standardization Not for Resale Foreword Iso (the International Organization for Standardization) is a woridwide 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 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. International Standard ISO 5315 was developed by Technical Committee ISO/TC 134, Fertilizers and soil conditioners, and was circulated to the member bodies in May 1982. It has been approved by the member bodies of the foliowing countries : China Kenya South Africa,Rep.of Czechoslovakia Korea, Rep. of Spain Egypt, Arab Rep. of Mexico Sri Lanka France Netherlands Thailand Germany, F.R. New Zealand United Kingdom Hungary Norway USA India Poland USSR Italy Portugal No member body expressed disapproval of the document. International Organization for Standardization, 1984 ? Printed in Switzerland Copyright International Organization for Standardization INTERNATIONAL STANDARD ISO 5315-1984 (E) Fertilizers - Determination of total nitrogen content - Titrimetric method after distillation 1 Scope and field of application 1,84 g/ml. This International Standard specifies a titrimetric method, after distillation, for the determination of the total nitrogen content of fertilizers in all forms, including those which have to be 3.7 Hydrochloric acid, concentrated, α approximately digested. 1,18 g/ml. The method is not recommended for fertilizers containing more thian 7 % of organic matter. 3.8 Sodium hydroxide, approximately 400 g/l solution. 2 Principle 3.9 Sodium hydroxide, standard volumetric solution, c(NaOH) = 0,10 mol/1.1) Reduction'of nitrate to ammonia by chromium powder in acid medium. Conversion of organic and urea nitrogen into am- monium suifate by digestion with concentrated sulfuric acid in 3.10 Sulfuric acid, standard volumetric solution, the presence of a catalyst. Distillation of the ammonia from an c(H2SO4) = 0,25 mol/1. 2) alkaline solution, absorption in an excess of standard volu- metric suifuric acid solution and back-titration with standard volumetric sodium hydroxidesolution in the presence of methyl 3.11 Sulfuric acid, standard volumetric solution, red or screened methyl red as indicator. c(H2SO4) = 0,10 mol/l.3) 3 Reagents 3.12 Sulfuric acid, standard volumetric solution, c(H2SO4) = 0,05 mol/1.1) During the analysis, use only reagents of recognized analytical grade having, in particular, low nitrogen contents (see 5.3), and only distilled water or water of equivalent purity. 3.13 Indicator, solution. Chromium metal, powder, of particle size less than or Use either the screened methyl red solution (3.13.1) or the 3.1 methyl red solution (3.13.2). equal to 250 μm. 3.2 Aluminium oxide, fused. Pumice is suitable. 3.13.1 Screened methyl red, ethanolic indicator solution. 3.3 Anti-foaming agent, for example paraffin wax of Mix 50 ml of a 2 g/l ethanolic solution of methyi red with 50 ml melting point not lower than 100 C, or a silicone. of a 1 g/l ethanolic solution of methylen