FprEN 15925

• Abstract:

  This document specifies a method for the extraction of the total sulfur contained in inorganic fertilizers in elemental form and/or in other chemical combinations.; The method is applicable to inorganic fertilizers for which a declaration of the total sulfur present in various forms (elemental, thiosulfate, sulfite, sulfate) is provided.

• Status: Not Published
• Publication Date: 13-Jan-2027
• ICS: 65.080 - Fertilizers
• Technical Committee: CEN/TC 260 - Fertilizers and liming materials
• Drafting Committee: CEN/TC 260/WG 7 - Chemical analysis
• Current Stage: 5020 - Submission to Vote - Formal Approval
• Start Date: 24-Sep-2026
• Due Date: 12-Mar-2027
• Completion Date: 24-Sep-2026
• Directive: 2019/1009 - Regulation (EU) 2019/1009 of the European Parliament and of the Council of 5 June 2019 laying down rules on the making available on the market of EU fertilising products and amending Regulations (EC) No 1069/2009 and (EC) No 1107/2009 and repealing Regulation (EC) No 2003/2003 (Text with EEA relevance)
• Mandate: M/564 - Fertilising products in support of Regulation (EU) 2019/1009
• Mandate: M/564 AMD 1 - amending Implementing Decision C(2020) 612 as regards certain harmonised standards and standardisation deliverables, deadlines for their adoption and the duration of the validity of the standardisation request
• Mandate: M/564 AMD 2 - Commission Implementing decision amending Implementing Decision C(2020)612 as regards harmonised standards, the deadlines for the adoption of those standards and the duration of the validity of the standardisation request to the European Committee for Standardisation as regards the EU fertilising products in support of Regulation (EU) 2019/1009 of the European Parliament and of the Council
• Ref Project: kSIST FprEN 15925:2026 - Inorganic fertilizers - Extraction of total sulfur present in various forms

• Revises: EN 15925:2011 - Fertilizers - Extraction of total sulfur present in various forms
• Effective Date: 02-Apr-2025

FprEN 15925 is a CEN draft European Standard for inorganic fertilizers. It specifies a laboratory method for extracting total sulfur present in elemental form and in other chemical combinations, so the sulfur can then be determined after oxidation to sulfate. It is intended for inorganic fertilizers where the total sulfur is declared in forms such as elemental sulfur, thiosulfate, sulfite, and sulfate.

What does FprEN 15925 specify?

FprEN 15925 specifies the scope, the extraction principle, the required reagents and apparatus, the step-by-step laboratory procedure, and the minimum contents of the test report. It is a method standard focused on sample preparation and extraction, not on sampling in the field.

The document is organized into these main parts:

• Scope
• Normative references
• Terms and definitions
• Sampling and sample preparation
• Principle
• Reagents
• Apparatus
• Procedure
• Test report
• Bibliography

The method applies to inorganic fertilizers for which a declaration of total sulfur in different forms is provided. In practice, that means the method is meant for products where sulfur may be present in more than one chemical form and has to be converted into a common analytical form before sulfate determination.

What are the key requirements of FprEN 15925?

FprEN 15925 requires the analyst to work on a representative laboratory sample and to follow a defined extraction and oxidation sequence before sulfate measurement. The practical purpose is to convert all relevant sulfur forms into sulfate in a controlled way, so the result reflects total sulfur in the declared forms.

Sampling and sample preparation

Sampling is not part of FprEN 15925. The laboratory sample should be representative and unchanged during transport or storage, and sample preparation shall follow EN 1482-2. Grinding is recommended for homogeneity, which matters because uneven particles can give uneven sulfur results.

Principle of the method

FprEN 15925 first converts elemental sulfur in alkaline medium into polysulfides and thiosulfate, then oxidizes these and any sulfites with hydrogen peroxide. The resulting sulfate is then determined as described in EN 15749. In practice, this is the core analytical logic: convert different sulfur forms into one measurable form.

Reagents and water quality

Only recognized analytical-grade reagents and distilled or demineralized water are to be used. The water must meet the stated conductivity limit, which helps avoid contamination that could affect sulfate determination. The reagent list includes diluted hydrochloric acid, sodium hydroxide solution, hydrogen peroxide solution, and barium chloride solution.

Test portion and oxidation

The test portion is weighed to an accuracy of 1 mg and must contain a defined sulfur range. A usual test portion is 2.5 g when sulfur is below 15 %. The sample is treated with sodium hydroxide solution and water, boiled under a watch glass, washed down from the beaker sides, and then oxidized with hydrogen peroxide until no reaction is seen. This stepwise heating and oxidation is what drives conversion to sulfate.

Preparation for sulfate determination

After oxidation, the solution is acidified with hydrochloric acid solution and handled differently depending on sulfur content. For sulfur below 5 %, the whole filtrate is used after checking that sulfate is absent in the last drops of filtrate; for sulfur at or above 5 %, the solution is made up to volume in a volumetric flask and an aliquot is taken. In both cases, sulfate is determined in accordance with EN 15749.

Test report

The report has to identify the method used, the sample, the sampling date and procedure if known, the date the extraction finished, and any optional steps or incidents that may have influenced the result. This is important for traceability and for comparing results between laboratories.

What terms does FprEN 15925 define?

FprEN 15925 uses the terms and definitions from EN 12944-1 and EN 12944-2.

• Total sulfur - the sulfur present in the fertilizer in the forms covered by the method and prepared for conversion to sulfate.
• Elemental sulfur - sulfur in its elemental form, which the method converts in alkaline medium before oxidation.
• Thiosulfate - a sulfur-containing form that is included in the extraction target and then oxidized to sulfate.
• Sulfite - another sulfur form that is oxidized during the method so it can be measured as sulfate.
• Sulfate - the final analytical form used for determination in EN 15749.
• Laboratory sample - the sample portion received by the laboratory for analysis and preparation.
• Test portion - the weighed portion taken from the laboratory sample for the extraction procedure.

Who uses FprEN 15925?

FprEN 15925 is used by fertilizer testing laboratories, fertilizer manufacturers, and quality control teams that need to check declared sulfur forms in inorganic fertilizers. It is also relevant for buyers, inspection bodies, and conformity assessment work where a common laboratory method is needed for comparing results.

What changed in FprEN 15925 from the previous edition?

FprEN 15925 will supersede EN 15925:2011. The foreword states three technical changes: the reference to EC fertilizer was removed, quality parameters for distilled water were added, and clarification was added for covering with a watch glass.

Which standards are used with FprEN 15925?

FprEN 15925 cites these companion standards and references:

• EN 1482-2 - gives general sample preparation provisions for fertilizers, liming materials, and inhibitors.
• EN 12944-1 - provides general terms for fertilizers and liming materials.
• EN 12944-2 - provides fertilizer-specific vocabulary.
• EN 15749 - gives the sulfate determination method used after extraction.
• EN 1482-1 - is listed in the bibliography as the recommended general sampling provision.

What does the FprEN 15925 document contain?

FprEN 15925 contains a practical laboratory method with a defined reagent set, basic apparatus, and a detailed heating, oxidation, filtration, and dilution sequence. It also gives a branch in the procedure for lower and higher sulfur levels, including the check for sulfate in the filtrate and the use of a volumetric flask for higher sulfur content.

The document is written to support routine laboratory testing, so the important deliverable is not a calculation formula but a reproducible preparation of the solution to be analyzed. The test report section then captures the information needed to trace how that solution was prepared and under what conditions.

SLOVENSKI STANDARD
oSIST prEN 15925:2026
01-februar-2026
Anorganska gnojila - Ekstrakcija celotnega žvepla v različnih oblikah
Inorganic fertilizers - Extraction of total sulfur present in various forms
Anorganische Düngemittel - Extraktion von Gesamtschwefel, der in verschiedener Form
vorliegen kann
Engrais inorganiques - Extraction du soufre total présent sous différentes formes
Ta slovenski standard je istoveten z: prEN 15925
ICS:
65.080 Gnojila Fertilizers
oSIST prEN 15925:2026 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

oSIST prEN 15925:2026
oSIST prEN 15925:2026
DRAFT
EUROPEAN STANDARD
prEN 15925
NORME EUROPÉENNE
EUROPÄISCHE NORM
December 2025
ICS 65.080 Will supersede EN 15925:2011
English Version
Inorganic fertilizers - Extraction of total sulfur present in
various forms
Engrais inorganiques - Extraction du soufre total Anorganische Düngemittel - Extraktion von
présent sous différentes formes Gesamtschwefel, der in verschiedener Form vorliegen
kann
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee
CEN/TC 260.
If this draft becomes a European Standard, CEN members are bound to comply with the CEN/CENELEC Internal Regulations
which stipulate the conditions for giving this European Standard the status of a national standard without any alteration.

This draft European Standard was established by CEN in three official versions (English, French, German). A version in any other
language made by translation under the responsibility of a CEN member into its own language and notified to the CEN-CENELEC
Management Centre has the same status as the official versions.

CEN members are the national standards bodies of Austria, Belgium, Bulgaria, Croatia, Cyprus, Czech Republic, Denmark, Estonia,
Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway,
Poland, Portugal, Republic of North Macedonia, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Türkiye and
United Kingdom.
Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are
aware and to provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without
notice and shall not be referred to as a European Standard.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2025 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 15925:2025 E
worldwide for CEN national Members.

oSIST prEN 15925:2026
prEN 15925:2025 (E)
Contents Page
European foreword . 3
1 Scope . 4
2 Normative references . 4
3 Terms and definitions . 4
4 Sampling and sample preparation . 4
5 Principle . 4
6 Reagents . 4
7 Apparatus . 5
8 Procedure . 5
8.1 Test portion . 5
8.2 Oxidation . 5
8.3 Preparation of the solution to be analysed . 5
9 Test report . 6
Bibliography . 7

oSIST prEN 15925:2026
prEN 15925:2025 (E)
European foreword
This document (prEN 15925:2025) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
This document is currently submitted to CEN Enquiry.
This document will supersede EN 15925:2011.
This document includes the following significant technical changes with respect to EN 15925:2011:
a) reference to EC fertilizer removed;
b) quality parameters for distilled water added;
c) clarification for covering with watch gl
...