🌱 Nitric and ammoniacal nitrogen in fertilizers according to Devarda — PN-EN 15476

Physicochemistry PN-EN 15476

Overview

WHAT THIS TEST IS — SCOPE FROM THE PKN CARD (Polish version), IN FULL: "W niniejszej Normie Europejskiej określono metodę oznaczania azotu azotanowego i amonowego z redukcją z użyciem stopu Devarda (zmodyfikowana dla każdego z wariantów a, b i c). Metoda ma zastosowanie do wszystkich nawozów azotowych, w tym nawozów wieloskładnikowych, w których azot występuje wyłącznie w formie azotanowej lub w formie amonowej i azotanowej" [This European Standard specifies a method for the determination of nitric and ammoniacal nitrogen with reduction using Devarda's alloy (modified for each of variants a, b and c). The method is applicable to all nitrogenous fertilizers, including compound fertilizers, in which nitrogen occurs exclusively in nitric form or in ammoniacal and nitric form]. The same scope stands in clause 1 of the text of EN 15476:2009.

A SCOPE BOUNDARY THAT IS EASY TO OVERLOOK: the word "wyłącznie" [exclusively]. A fertilizer in which, besides nitrates and ammonium salts, there is urea, cyanamide or organic nitrogen does not meet the condition of the scope — this standard does not cover such a product. In accreditation scopes the subject of the test is sometimes entered collectively (in one entry together with urea, compost and organic fertilizers) — this is a description of the laboratory's group of products, not an extension of the scope of the standard.

PRINCIPLE (clause 4). Nitrates and nitrites are reduced to ammonia in a strongly alkaline solution with a metal alloy composed of 45 % Al, 5 % Zn and 50 % Cu (Devarda's alloy). The ammonia is 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. In the strongly alkaline solution the ammonia from ammonium salts also distils off, which is why the result covers nitric and ammoniacal nitrogen together — accreditation scopes call it outright "sumą zawartości azotu azotanowego i amonowego" [the sum of the nitric and ammoniacal nitrogen content]. Ammoniacal nitrogen alone is determined by PN-EN 15475 (a separate entry in this database).

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. The hydroxide solutions are to be free from carbonates. The test portion (5 g, 7 g or 10 g — 8.1) and the aliquot of the solution taken for distillation (Tables 1–3) also depend on the variant.

DEVARDA'S ALLOY — THE REQUIREMENT THAT DECIDES THE REDUCTION (5.9): a powder of which 90 % to 100 % by mass passes through a sieve with apertures smaller than 0.25 mm, and 50 % to 75 % by mass — through a sieve with apertures smaller than 0.075 mm. The standard recommends factory-packed bottles containing at most 100 g. 4 g of the alloy are added to one distillation (8.2).

PREPARATION OF THE SOLUTION (8.1). The test portion (5 g, 7 g or 10 g, weighed to the nearest 0.001 g) is transferred to a 250 ml beaker, about 50 ml of water and 20 ml of hydrochloric acid diluted 1 + 1 are added, the beaker is covered, heated to boiling and cooled. The contents are filtered into a 500 ml volumetric flask together with the washing water, made up to the mark and mixed.

DISTILLATION (8.2). The quantity of nitric nitrogen in the aliquot must not exceed the maximum from Tables 1–3. The sulfuric acid of the variant, the indicator and water to 50 ml are accurately measured into the receiver; the end of the condenser extension is to be below the surface of the liquid, and the bubble trap — filled with water. Into the distillation flask: an aliquot of the solution taken with a pipette, water to a volume of 250 ml to 300 ml, 5 ml of ethanol, 4 g of Devarda's alloy, about 30 ml of 30 % sodium hydroxide solution and — for samples dissolved in acid — an additional quantity neutralizing the hydrochloric acid of the aliquot. The flask is heated gently, so that the evolution of hydrogen decreases markedly within about half an hour and the liquid begins to boil; then more strongly, so that at least 200 ml of liquid distil over in about 30 min. The distillation is not prolonged beyond 45 min. After the receiver is disconnected, the extension and the trap are rinsed, and the excess acid is titrated with the hydroxide solution appropriate to the variant.

EDITIONS (state of the PKN cards on 25.09.2026). PN-EN 15476:2009 — English version: publication 16-02-2009, 13 pages; Polish version: publication 23-09-2014, 16 pages; both KT 156 Fertilizers, both introduce EN 15476:2009 [IDT], both without the "Wycofana" [Withdrawn] header. At the publisher (the CEN catalogue run by iTeh, read on 25.09.2026): EN 15476:2009 published 21-01-2009, replaced CEN/TS 15476:2006; stage 90.93 — decision to confirm the standard 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): 19 entries at 19 laboratories, all with the single notation "PN-EN 15476:2009". The subject of the test is most often "Nawozy mineralne (nieorganiczne)" [Mineral (inorganic) fertilizers] (15 entries); the methodology most often "Zawartość azotu azotanowego i amonowego wg Devarda" [Nitric and ammoniacal nitrogen content according to Devarda] (7), in three entries spelled "Dewarda"; the technique "Metoda miareczkowa" [Titrimetric method] (17 entries, 2 without a technique). The declared ranges have lower limits from 0.40 % to 4.50 %, and upper ones from 20.0 % to 50.0 %. No other document stands in the same entries.

THE KEY OF THE "LABORATORIES" TAB: "PN-EN 15476" — 19 laboratories and 19 entries, without foreign entries.

WHAT WE DO NOT GIVE. We had a fragment of the text of EN 15476:2009 made available by the publisher: the foreword, the table of contents and clauses 1–8.2. We do not have Tables 1–3 (test portions, aliquots, maximum quantities of nitrogen and volumes of acid for the variants), the clauses from 8.3 onwards (among others Note 2 in 8.4, to which the reagents of variants b and c refer), the calculation formula (clause 9) or the precision data (clause 10 and Annex A). What the sodium nitrate listed in 5.13 is used for is not in the fragment read. Therefore we do not give the volumes of the aliquots, the formula or the repeatability limits.

Method principle

Nitrates and nitrites are reduced to ammonia with Devarda's alloy (45 % Al, 5 % Zn, 50 % Cu) in a strongly alkaline solution; the ammonia — together with the ammonia from ammonium salts — is 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 (mixed indicator or methyl red).

Applications

• Nitrogenous fertilizers in which nitrogen occurs exclusively in nitric form or in ammoniacal and nitric form (e.g. nitrates, calcium ammonium nitrates, compound fertilizers with such nitrogen)
• Checking the declared nitrogen content before a fertilizer is placed on the market and in official control
• Pair with PN-EN 15475: the sum of nitric and ammoniacal nitrogen (this standard) and ammoniacal nitrogen alone (PN-EN 15475)

Key parameters

Standard

Standard number

PN-EN 15476:2009 (wersja polska z 2014 r. i wersja angielska z 2009 r.; wprowadza EN 15476:2009 [IDT])

Title (PL)

Nawozy — Oznaczanie azotu azotanowego i amonowego według Devarda

Title (EN)

Fertilizers — Determination of nitric and ammoniacal nitrogen according to Devarda

Step-by-step procedure

1. Sample

   Preparation of the sample according to EN 1482-2; sampling is not part of the method.

2. Choice of the variant

   Choose variant a, b or c — the test portion, the aliquot and the concentrations of the standard volumetric solutions depend on it (Tables 1–3, which WE DO NOT GIVE).

3. Sample solution

   Heat the test portion (5 g, 7 g or 10 g ± 0.001 g) with approx. 50 ml of water and 20 ml of HCl 1 + 1 to boiling under a cover, cool, filter into a 500 ml flask, make up with water.

   🌡 Temperature: to boiling

4. Receiver

   Accurately measure the sulfuric acid of the variant, add the indicator and water to 50 ml; the end of the condenser extension below the surface of the liquid, the trap filled with water.

5. Distillation flask

   Aliquot of the solution (with a pipette), water to 250–300 ml, 5 ml of ethanol, 4 g of Devarda's alloy; carefully approx. 30 ml of NaOH 30 % and the quantity neutralizing the HCl; connect tightly and mix.

6. Reduction and distillation

   Gentle heating until the evolution of hydrogen decreases markedly (about half an hour) and the liquid begins to boil; then at least 200 ml of distillate in approx. 30 min, in total not longer than 45 min.

   ⏱ Time: approx. 30 min of reduction + approx. 30 min of distillation (max. 45 min)

7. Titration

   Rinse the extension and the trap into the receiver, titrate the excess acid with the NaOH or KOH solution of the variant. WE DO NOT GIVE the calculation formula (clause 9).

Required equipment and apparatus

Reagents, media and consumables

Health and safety (OHS)

• Sodium hydroxide solution 30 % — corrosive; add carefully, wearing goggles and gloves
• During reduction with Devarda's alloy hydrogen is evolved (8.2) — a flammable gas; gentle heating, efficient ventilation
• Tight joints of the apparatus and the water trap protect against loss of ammonia — a leak lowers the result

Frequently asked questions