🌱 Ammoniacal nitrogen in fertilizers (distillation with sodium hydroxide) — PN-EN 15475

Physicochemistry PN-EN 15475

Overview

WHAT THIS TEST IS — SCOPE FROM THE PKN CARD, IN FULL: "W niniejszej Normie Europejskiej określono metodę oznaczania zawartości azotu amonowego w nawozach. Metoda ma zastosowanie do wszystkich nawozów azotowych, łącznie z nawozami wieloskładnikowymi, w których azot występuje wyłącznie w postaci soli amonowych lub soli amonowych wraz z azotanami. Niniejszej Normy Europejskiej nie stosuje się do nawozów zawierających mocznik, cyjanamid lub inne organiczne związki azotowe" [This European Standard specifies a method for the determination of the ammoniacal nitrogen content of fertilizers. The method is applicable to all nitrogenous fertilizers, including compound fertilizers, in which nitrogen occurs exclusively in the form of ammonium salts or ammonium salts together with nitrates. This European Standard is not applicable to fertilizers containing urea, cyanamide or other organic nitrogen compounds]. The same scope stands in clause 1 of the text of EN 15475:2009.

WHY THE EXCLUSION OF UREA MATTERS WHEN PLACING AN ORDER. In accreditation scopes the subject of the test is sometimes entered collectively — in one entry together with urea, compost and organic fertilizers. The standard itself, however, explicitly excludes fertilizers containing urea, cyanamide or other organic nitrogen compounds. When ordering the determination of ammoniacal nitrogen in a fertilizer with urea, one has to ask the laboratory according to which document it will perform it.

PRINCIPLE (clause 4). Ammonia is displaced from the sample with an excess of sodium hydroxide, distilled off and absorbed in a measured volume of standard volumetric sulfuric acid; the excess acid is titrated with a standard volumetric solution of sodium or potassium hydroxide. Unlike PN-EN 15476, there is no reduction of nitrates here — nitric nitrogen does not enter the result.

THREE VARIANTS — DIFFERENT CONCENTRATIONS OF THE STANDARD VOLUMETRIC SOLUTIONS (5.3–5.8): variant a — sulfuric acid 0.05 mol/l and sodium or potassium hydroxide 0.1 mol/l; variant b — 0.1 mol/l and 0.2 mol/l; variant c — 0.25 mol/l and 0.5 mol/l; hydroxides free from carbonates. The other reagents: hydrochloric acid diluted 1 + 1, sodium hydroxide 30 % (ρ ≈ 1.33 g/ml) free from ammonia, mixed indicator (methyl red with methylene blue) or methyl red, anti-bumping granules (e.g. pumice, glass beads — washed with hydrochloric acid and ignited) and ammonium sulfate, analytical grade. Water — grade 3 according to EN ISO 3696, free from carbon dioxide and nitrogen compounds.

DISTILLATION APPARATUS (6.1). A round-bottomed flask connected to the condenser through a splash head, all of borosilicate glass; in Figures 1–4 the standard shows four recommended types of apparatus. Figure 1: a 1000 ml flask with a long neck, a dropping funnel with a PTFE stopcock for dispensing sodium hydroxide, a six-bulb condenser and a 500 ml receiver. An automatic apparatus is permitted if it gives statistically equivalent results.

EDITIONS (state of the PKN cards on 25.09.2026). PN-EN 15475:2009 — English version: publication 16-02-2009, 15 pages; Polish version: publication 24-09-2014, 18 pages; both KT 156 Fertilizers, both introduce EN 15475:2009 [IDT], both without the "Wycofana" [Withdrawn] header. At the publisher (the CEN catalogue run by iTeh, read on 25.09.2026): EN 15475:2009 published 21-01-2009, replaced CEN/TS 15475:2006; stage 90.93 — decision to confirm after the systematic review (enquiry from 05-02-2025, closing 23-09-2026).

HOW ACCREDITATION SCOPES CITE THE STANDARD. Measurement of 25.09.2026 on the database of PL accreditation scopes (1310 laboratories with entries): 18 entries at 18 laboratories; notation "PN-EN 15475:2009" (17) and once "PN-EN 15475: 2009" with a space. The subject of the test is most often "Nawozy mineralne (nieorganiczne)" [Mineral (inorganic) fertilizers] (14 entries); the methodology most often "Zawartość azotu amonowego" [Ammoniacal nitrogen content] (13); the technique "Metoda miareczkowa" [Titrimetric method] (16 entries, 2 without a technique). The declared ranges have lower limits from 0.050 % to 4.50 %, and upper ones from 20.0 % to 50.0 %. In one entry PN-EN 15604:2012 stands alongside this standard.

THE KEY OF THE "LABORATORIES" TAB: "PN-EN 15475" — 18 laboratories and 18 entries, without foreign entries (the notation with a space after the colon also fits).

WHAT WE DO NOT GIVE. We had a fragment of the text of EN 15475:2009 made available by the publisher: the foreword, the table of contents, clauses 1–5 and the beginning of clause 6 with Figures 1 and 2 of the apparatus. We do not have the course of the determination (clause 8 — test portions, aliquots, distillation time), the formula (clause 9) or the precision data (clause 10 and Annex A). Therefore we do not give the test portions, volumes, distillation time or formula.

Method principle

Ammonia is displaced from the sample solution with an excess of sodium hydroxide, distilled into a known volume of standard volumetric sulfuric acid, and the excess acid is titrated with a standard volumetric solution of sodium or potassium hydroxide. Without reduction of nitrates — only ammoniacal nitrogen is determined.

Applications

• Nitrogenous fertilizers, also compound ones, with nitrogen exclusively in the form of ammonium salts or ammonium salts and nitrates (e.g. ammonium sulfate, ammonium nitrate, calcium ammonium nitrates)
• Checking the declared ammoniacal nitrogen content
• Pair with PN-EN 15476: ammoniacal nitrogen (this standard) and the sum of nitric and ammoniacal nitrogen (PN-EN 15476)
• NOT for fertilizers with urea, cyanamide and other organic nitrogen compounds

Key parameters

Standard

Standard number

PN-EN 15475:2009 (wersja polska z 2014 r. i wersja angielska z 2009 r.; wprowadza EN 15475:2009 [IDT])

Title (PL)

Nawozy — Oznaczanie azotu amonowego

Title (EN)

Fertilizers — Determination of ammoniacal nitrogen

Step-by-step procedure

1. Sample

   Preparation of the sample according to EN 1482-2 (standard referenced in clause 2).

2. Whether the fertilizer falls within the scope

   Check that the nitrogen is exclusively in the form of ammonium salts or ammonium salts and nitrates; a fertilizer with urea, cyanamide or organic nitrogen — outside the scope.

3. Choice of the variant

   Variant a, b or c — the concentrations of the standard volumetric solutions depend on it. WE DO NOT GIVE the test portions and aliquots (clause 8).

4. Distillation

   Displace the ammonia with an excess of NaOH 30 % and distil it into a measured volume of standard volumetric sulfuric acid in an apparatus according to Figures 1–4 or in an automatic apparatus with equivalent results. WE DO NOT GIVE the time and the volume of distillate.

5. Titration and result

   Titrate the excess acid with the standard volumetric NaOH or KOH of the variant. WE DO NOT GIVE the formula (clause 9) and the repeatability limits (clause 10).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Sodium hydroxide solution 30 % — corrosive; dispense through the dropping funnel, wearing goggles and gloves
• Anti-bumping granules prevent violent boiling in the distillation flask
• The tightness of the apparatus determines the result — every loss of ammonia lowers the nitrogen content

Frequently asked questions