EN 15956:2011 – Fertilizers – Extraction of phosphorus soluble in mineral acids
1 Scope
This document specifies a method for the determination of phosphorus soluble in mineral acids.
The method is applicable exclusively to phosphate fertilizers listed in Regulation (EC) 2003/2003, Annex I (see [2]).
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenceddocument (including any amendments) applies.
EN 1482-2, Fertilizers and liming materials — Sampling and sample preparation — Part 2: Sample preparation
EN 12944-1:1999, Fertilizers and liming materials and soil improvers — Vocabulary — Part 1: General terms
EN 12944-2:1999, Fertilizers and liming materials and soil improvers — Vocabulary — Part 2: Terms relating to fertilizers
3 Terms and definitions
For the purposes of this document, the terms and definitions given in EN 12944-1:1999 and EN 12944-2:1999 apply.
4 Principle
Extraction of the phosphorus in the fertilizer with a mixture of nitric acid and sulfuric acid under the specified conditions.
5 Sampling
Sampling is not part of the method specified in this document. A recommended sampling method is given in EN 1482-1.
Sample preparation shall be carried out in accordance with EN 1482-2. Grinding of the laboratory sample is recommended for homogeneity reasons.
6 Reagents
6.1 Water, distilled or demineralized.
6.2 Sulfuric acid, ρ = 1,84 g/ml.
6.3 Nitric acid, ρ = 1,40 g/ml.
7 Apparatus
7.1 Standard laboratory equipment.
7.2 Kjeldahl flask, capacity at least 500 ml, or 250 ml round-bottomed flask with a glass tube forming a reflux condenser.
7.3 500 ml graduated flask.
7.4 Dry pleated filter, phosphate free.
8 Procedure
8.1 Test portion
Weigh, to the nearest 0,001 g, 2,5 g of the laboratory sample and place it in a dry Kjeldahl flask (7.2).
8.2 Extraction
Add 15 ml of water (6.1) to the test portion and stir so as to suspend the substance. Add 20 ml of nitric acid (6.3) and carefully add 30 ml of sulfuric acid (6.2).
When the initial violent reaction has ceased, slowly bring the contents of the flask to boiling and boil for 30 min. Allow to cool and then carefully add with mixing about 150 ml of water (6.1). Continue boiling for 15 min.
Cool completely and transfer the liquid quantitatively to a graduated flask (7.3). Make up to volume, mix and filter through a dry pleated filter (7.4), discarding the first portion of the filtrate.
9 Test report
The test report shall contain at least the following information:
a) all information necessary for the complete identification of the sample;
b) test method used with reference to this document;
c) test results obtained;
d) date of sampling and sampling procedure (if known);
e) date when the analysis was finished;
f) whether the requirement of the repeatability limit has been fulfilled;
EN 15956:2011 – Fertilizers – Extraction of phosphorus soluble in mineral acids