CEN/TS 16198:2011

SLOVENSKI STANDARD
01-oktober-2011
*QRMLOD.RPSOHNVRPHWULMVNRGRORþHYDQMHPDJQH]LMD
Fertilizers - Determination of magnesium by complexometry
Düngemittel - Komplexometrische Bestimmung von Magnesium
Engrais - Dosage du magnésium par complexométrie
Ta slovenski standard je istoveten z: CEN/TS 16198:2011
ICS:
65.080 Gnojila Fertilizers
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CEN/TS 16198
SPÉCIFICATION TECHNIQUE
TECHNISCHE SPEZIFIKATION
June 2011
ICS 65.080
English Version
Fertilizers - Determination of magnesium by complexometry
Engrais - Dosage du magnésium par complexométrie Düngemittel - Komplexometrische Bestimmung von
Magnesium
This Technical Specification (CEN/TS) was approved by CEN on 5 March 2011 for provisional application.

The period of validity of this CEN/TS is limited initially to three years. After two years the members of CEN will be requested to submit their
comments, particularly on the question whether the CEN/TS can be converted into a European Standard.

CEN members are required to announce the existence of this CEN/TS in the same way as for an EN and to make the CEN/TS available
promptly at national level in an appropriate form. It is permissible to keep conflicting national standards in force (in parallel to the CEN/TS)
until the final decision about the possible conversion of the CEN/TS into an EN is reached.

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, Romania, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2011 CEN All rights of exploitation in any form and by any means reserved Ref. No. CEN/TS 16198:2011: E
worldwide for CEN national Members.

Contents Page
Foreword .3
1 Scope .4
2 Normative references .4
3 Terms and definitions .4
4 Principle .4
5 Sampling .4
6 Reagents .5
7 Apparatus .6
8 Preparation of the extraction solution .6
9 Procedure .6
9.1 Control test .6
9.2 Aliquot samples to be taken .7
9.3 Titration in the presence of Eriochrome black-T .7
9.4 Titration in the presence of calcein or of calcon carbonic acid .7
10 Calculation and expression of the result .7
11 Remarks .7
12 Precision .8
12.1 Inter-laboratory test .8
12.2 Repeatability .8
12.3 Reproducibility .8
13 Test report .9
Annex A (informative) Statistical results of the inter-laboratory test . 10
Bibliography . 12

Foreword
This document (CEN/TS 16198:2011) has been prepared by Technical Committee CEN/TC 260 “Fertilizers
and liming materials”, the secretariat of which is held by DIN.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent rights.
This document has been prepared under a mandate given to CEN by the European Commission and the
European Free Trade Association.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to announce this Technical Specification: 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, Romania, Slovakia, Slovenia,
Spain, Sweden, Switzerland and the United Kingdom.
1 Scope
This Technical Specification specifies a method for the determination of magnesium in fertilizer extracts.
The method is applicable to the following EC fertilizer extracts for which the determination of total magnesium
and/or water-soluble magnesium is provided for according to the Regulation (EC) No 2003/2003, Annex I [3]:
 fertilizers listed in [3], Annex I: straight nitrogenous fertilizers, type 1b + 1c (calcium magnesium nitrate),
type 7 (magnesium sulfonitrate), type 8 (nitrogenous fertilizers with magnesium) and straight potassic
fertilizers, type 2 (enriched kainite), type 4 (potassium chloride containing magnesium), type 6 (potassium
sulfate containing magnesium salt);
 fertilizers listed in [3], Annex I D relating to secondary nutrients.
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 referenced
document (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
CEN/TS 15960, Fertilizers — Extraction of total calcium, total magnesium, total sodium and total sulfur in the
forms of sulfates
CEN/TS 15961, Fertilizers — Extraction of water soluble calcium, magnesium, sodium and sulfur in the form
of sulfates
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
The magnesium is solubilized according to CEN/TS 15960 or CEN/TS 15961. First titration: with EDTA of Ca
and Mg in the presence of Eriochrome black-T. Second titration: with EDTA of Ca in the presence of calcein
or of calcone carbonic acid. Determination of magnesium by difference.
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 Magnesium standard solution, c = 0,05 mol/l.
6.1.1 Dissolve 1,232 g of magnesium sulfate (MgSO 7H O) in the hydrochloric acid solution (6.11) and
4 2
make up to 100 ml with the same acid,
or
6.1.2 Weigh 2,016 g of magnesium oxide, previously calcined to remove all traces of carbonation. Place it
in a beaker with 100 ml of water.
Stir in approximately 120 ml of hydrochloric acid (6.12).
After dissolution, transfer quantitatively into a graduated 1 000 ml flask. Make up to volume and mix.
1 ml of these solutions should contain 1,216 mg of Mg (= 2,016 mg of MgO).
The laboratory is responsible for testing the strength of this standard solution.
6.2 EDTA solution, c = 0,05 mol/l.
Weigh 18,61 g of the dihydrated disodium salt of ethylenediaminetetraacetic (EDTA) (C H N Na O ,2H O),
10 14 2 2 8 2
place it in a beaker (7.4) and dissolve in 600 ml to 800 ml of water. Transfer the solution quantitatively into a
graduated flask (7.3). Make up the volume and mix. Check this solution with the standard solution (6.1) by
taking a sample of 20 ml of the latter and by titration according to the analytical procedure described in 9.2.
1 ml of the EDTA solution should correspond to 1,216 mg of Mg (= 2,016 mg of MgO) and to 2,004 mg of Ca
(= 2,804 mg CaO) (see remarks 11.1 and 11.6).
6.3 Calcium standard solution, c = 0,05 mol/l.
Weigh 5,004 g of dry calcium carbonate. Place it in a beaker with 100 ml of water. Progressively stir in 120 ml
of hydrochloric acid (6.12).
Bring to the boil in order to drive off the carbon dioxide, cool, transfer quantitatively into a graduated 1 l flask,
make up the volume with water and mix. Check this solution against the EDTA solution (6.2) following
analytical procedure (9.3). 1 ml of this solution should contain 2,004 mg of Ca (= 2,804 mg of CaO) and
should correspond to 1 ml of the EDTA solution (6.2).
6.4 Calcein indicator.
Carefully mix in a mortar 1 g of calcein with 100 g of sodium chloride. Use 10 mg of this mixture. The indicator
changes from green to orange. Titration shall be carried out until an orange is obtained which is free from
green tinges.
6.5 Calcon carbonic acid indicator.
Dissolve 400 mg of calcon carbonic in 100 ml of methanol. This solution may only be kept for approximately
four weeks. Use three drops of this solution. The indicator changes from red to blue. Titration shall be carried
out until a blue is obtained which is free from red tinges.
6.6 Eriochrome black-T indicator.
Dissolve 300 mg of Eriochrome black-T in a mixture of 25 ml of propanol-1 and 15 ml of triethanolamine. This
solution may only be kept for approximately four weeks. Use three drops of this solution. This indicator turns
from red to blue and titration shall be carried out until a blue is obtained which is free from red tinges. It
changes colour only when magnesium is present. If necessary add 1 ml of the magnesium standard solution
(6.1).
When both calcium and magnesium are present the EDTA first forms a complex with the calcium and then
with the magnesium. In that case two elements are determined concurrently.
6.7 Potassium cyanide solution, aqueous solution of w(KCN) = 2 %.
SAFETY PRECAUTIONS — Do not pipette by mouth and see 11.7.
6.8 Solution of potassium hydroxide and potassium cyanide.
Dissolve 280 g of KOH and 66 g of KCN in water, make up the volume to 1 l and mix.
6.9 Buffer solution, pH = 10,5.
In a graduated flask (7.5), dissolve 33 g of ammonium chloride in 200 ml of water, add 250 ml of ammonia
(ρ = 0,91 g/ml) make up the volume with water and mix. Check the pH of the solution regularly.
6.10 Diluted hydrochloric acid, one volume of hydrochloric acid (ρ = 1,18 g/ml) plus one volume of water.
6.11 Hydrochloric acid solution, approximately c = 0,5 mol/l.
6.12 Hydrochloric acid solution, approximately c = 1 mol/l.
6.13 Sodium hydroxide solution, c = 5 mol/l.
7 Apparatus
7.1 Magnetic or mechanical stirrer.
7.2 pH meter.
7.3 1 000 ml graduated flask.
7.4 1 000 ml beaker.
7.5 500 ml graduated flask.
7.6 400 ml beaker.
8 Preparation of the extraction solution
Prepare the extraction solution according to CEN/TS 15960 or CEN/TS 15961.
9 Procedure
9.1 Control test
Carry out a determination on aliquot parts of solutions (6.1 and 6.3) such that the Ca/Mg ratio is approximately
equal to that of the solution to be analyzed. To this end take v ml of Mg standard solution (6.3) and (v -v ) ml
1 2 1
of standard solution (6.1), where v and v are the volumes, in millilitres, of the EDTA solution used in the two
1 2
titrations performed on the solution to be analyzed. This procedure is correct only if the solutions of EDTA,
calcium and magnesium are exactly equivalent. If this is not the case, it is necessary to make corrections.
9.2 Aliquot samples to be taken
The aliquot part will as far as possible contain between 9 mg and 18 mg of magnesium (= 15 mg to 30 mg
of MgO).
9.3 Titration in the presence of Eriochrome black-T
Pipett
...