EN 17215:2019

Chemicals used for treatment of water intended for human consumption - Iron-based coagulants - Analytical methods

This document is applicable to iron-based coagulants used for treatment of water intended for human consumption. It specifies analytical methods to be used for products described in EN 888, EN 889, EN 890, EN 891 and EN 14664.

Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch - Flockungsmittel auf Eisenbasis - Analysenverfahren

Dieses Dokument gilt für Flockungsmittel auf Eisenbasis zur Aufbereitung von Wasser für den menschlichen Gebrauch. Es legt die anzuwendenden Analysenverfahren für Produkte fest, die in EN 888 (Eisen(III)chlorid), EN 889 (Eisen(II)sulfat), EN 890 (Eisen(III)sulfat-Lösung), EN 891 (Eisen(III)chloridsulfat) und EN 14664 (Eisen(III)sulfat, fest) beschrieben sind.

Produits chimiques utilisés pour le traitement de l'eau destinée à la consommation humaine - Coagulants à base de fer - Méthodes d'analyse

La présente Norme européenne est applicable aux coagulants à base de fer utilisés pour le traitement de l’eau destinée à la consommation humaine. Elle spécifie les méthodes d’analyse à utiliser pour les produits décrits dans l’EN 888, l’EN 889, l’EN 890, l’EN 891 et l’EN 14664.

Kemikalije, ki se uporabljajo za pripravo pitne vode - Sredstvo za strjevanje na osnovi železa - Analitske metode

Ta dokument se uporablja za sredstva za strjevanje na osnovi železa, ki se uporabljajo za pripravo pitne vode. Določa analitične metode, ki se uporabljajo za izdelke, opisane v standardih EN 888, EN 889, EN 890, EN 891 in EN 14664.

General Information

• Status: Published
• Publication Date: 19-Mar-2019
• Withdrawal Date: 29-Sep-2019
• ICS: 71.100.80 - Chemicals for purification of water
• Technical Committee: CEN/TC 164 - Water supply
• Drafting Committee: CEN/TC 164/WG 9 - Drinking water treatment
• Current Stage: 6060 - Definitive text made available (DAV) - Publishing
• Start Date: 20-Mar-2019
• Due Date: 06-Oct-2019
• Completion Date: 20-Mar-2019
• Ref Project: SIST EN 17215:2019 - Chemicals used for treatment of water intended for human consumption - Iron-based coagulants - Analytical methods

Standards Content (Sample)

SLOVENSKI STANDARD
SIST EN 17215:2019
01-maj-2019
Kemikalije, ki se uporabljajo za pripravo pitne vode - Sredstvo za strjevanje na
osnovi železa - Analitske metode

Chemicals used for treatment of water intended for human consumption - Iron-based

coagulants - Analytical methods
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch -
Flockungsmittel auf Eisenbasis - Analysenverfahren

Produits chimiques utilisés pour le traitement de l'eau destinée à la consommation

humaine - Coagulants à base de fer - Méthodes d'analyse
Ta slovenski standard je istoveten z: EN 17215:2019
ICS:
13.060.20 Pitna voda Drinking water
71.100.80 .HPLNDOLMH]DþLãþHQMHYRGH Chemicals for purification of
water
SIST EN 17215:2019 en,fr,de

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 17215:2019
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SIST EN 17215:2019
EN 17215
EUROPEAN STANDARD
NORME EUROPÉENNE
March 2019
EUROPÄISCHE NORM
ICS 71.100.80
English Version
Chemicals used for treatment of water intended for human
consumption - Iron-based coagulants - Analytical methods

Produits chimiques utilisés pour le traitement de l'eau Produkte zur Aufbereitung von Wasser für den

destinée à la consommation humaine - Coagulants à menschlichen Gebrauch - Flockungsmittel auf

base de fer - Méthodes d'analyse Eisenbasis - Analysenverfahren
This European Standard was approved by CEN on 10 December 2018.

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. Up-to-date lists and bibliographical references

concerning such national standards may be obtained on application to the CEN-CENELEC Management Centre or to any CEN

member.

This European Standard exists 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, Former Yugoslav Republic of Macedonia, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania,

Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland,

Turkey and United Kingdom.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION
EUROPÄISCHES KOMITEE FÜR NORMUNG
CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels

© 2019 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 17215:2019 E

worldwide for CEN national Members.
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SIST EN 17215:2019
EN 17215:2019 (E)
Contents Page

European foreword ............................................................................................................................................ 4

1 Scope .......................................................................................................................................................... 5

2 Normative references .......................................................................................................................... 5

3 Terms and definitions ......................................................................................................................... 5

4 Methods of analysis .............................................................................................................................. 6

5 Sampling ................................................................................................................................................... 8

5.1 General...................................................................................................................................................... 8

5.2 Solids ......................................................................................................................................................... 8

5.3 Solutions ................................................................................................................................................... 8

5.3.1 Sampling from drums and bottles .................................................................................................. 8

5.3.2 Sampling from tanks and tankers ................................................................................................... 8

6 Expression of results ........................................................................................................................... 9

6.1 Iron content ............................................................................................................................................ 9

6.2 Free acid ................................................................................................................................................... 9

6.3 Insoluble matters .................................................................................................................................. 9

6.4 Impurities ................................................................................................................................................ 9

6.5 Repeatability .......................................................................................................................................... 9

Annex A (normative) Analysis of the iron content ............................................................................... 10

A.1 Determination of iron (II) concentration by titration against cerium (IV) sulfate ..... 10

A.2 Determination of total iron ............................................................................................................. 11

A.3 Determination of iron (III) .............................................................................................................. 12

Annex B (informative) Alternative analysis of the iron content ..................................................... 13

B.1 Determination of iron (II) concentration by titration against potassium

dichromate ............................................................................................................................................ 13

B.2 Determination of iron (III) concentration by iodometric titration .................................. 14

Annex C (normative) Analysis of the chemical parameters and impurities ............................... 16

C.1 Determination of free acid .............................................................................................................. 16

C.2 Determination of insoluble matters ............................................................................................ 18

C.3 Determination of manganese by Flame Atomic Absorption Spectroscopy (FAAS) ..... 20

C.4 Determination of arsenic, antimony and selenium by hydride generation atomic

absorption spectrometry (HGAAS) ............................................................................................... 22

C.5 Determination of mercury by cold vapour atomic absorption spectrometry

(CVAAS) ................................................................................................................................................... 26

C.6 Determination of cadmium, chromium, nickel and lead by graphite furnace atomic

absorption spectrometry (GFAAS) ............................................................................................... 29

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Annex D (informative) Determination of arsenic, antimony, cadmium, chromium,
manganese, nickel and lead and selenium (inductively coupled plasma optical

emission spectrometry (ICP-OES)) ............................................................................................... 34

D.1 General ................................................................................................................................................... 34

D.2 Principle ................................................................................................................................................. 34

D.3 Reagents ................................................................................................................................................. 34

D.4 Apparatus .............................................................................................................................................. 35

D.5 Sample solution ................................................................................................................................... 36

D.6 Procedure .............................................................................................................................................. 36

D.7 Calculation and expression of results ......................................................................................... 37

Annex E (informative) Determination of arsenic, antimony, cadmium, lead and selenium

(inductively coupled plasma mass spectrometry (ICP-MS)) ............................................... 38

E.1 General ................................................................................................................................................... 38

E.2 Principle ................................................................................................................................................. 38

E.3 Reagents ................................................................................................................................................. 38

E.4 Apparatus .............................................................................................................................................. 39

E.5 Sample solution ................................................................................................................................... 39

E.6 Procedure .............................................................................................................................................. 39

E.7 Calculation and expression of results ......................................................................................... 40

Bibliography ....................................................................................................................................................... 41

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SIST EN 17215:2019
EN 17215:2019 (E)
European foreword

This document (EN 17215:2019) has been prepared by Technical Committee CEN/TC 164 “Water

supply”, the secretariat of which is held by AFNOR.

This European Standard shall be given the status of a national standard, either by publication of an

identical text or by endorsement, at the latest by September 2019, and conflicting national standards shall

be withdrawn at the latest by September 2019.

Attention is drawn to the possibility that some of the elements of this document may be the subject of

patent rights. CEN shall not be held responsible for identifying any or all such patent rights.

According to the CEN-CENELEC Internal Regulations, the national standards organisations of the

following countries are bound to implement this European Standard: Austria, Belgium, Bulgaria, Croatia,

Cyprus, Czech Republic, Denmark, Estonia, Finland, Former Yugoslav Republic of Macedonia, France,

Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands,

Norway, Poland, Portugal, Romania, Serbia, Slovakia, Slovenia, Spain, Sweden, Switzerland, Turkey and

the United Kingdom.
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EN 17215:2019 (E)
1 Scope

This document is applicable to iron-based coagulants used for treatment of water intended for human

consumption. It specifies analytical methods to be used for products described in EN 888 (Iron (III)

chloride), EN 889 (Iron (II) sulfate), EN 890 (Iron (II) sulfate, solution), EN 891 (Iron (III) chloride

sulfate) and EN 14664 (Iron (III) sulfate, solid).
2 Normative references

The following documents are referred to in the text in such a way that some or all of their content

constitutes requirements 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 ISO 3696, Water for analytical laboratory use - Specification and test methods (ISO 3696:1987)

ISO 3165, Sampling of chemical products for industrial use — Safety in sampling
ISO 6206, Chemical products for industrial use — Sampling — Vocabulary

ISO 8213, Chemical products for industrial use — Sampling techniques — Solid chemical products in the

form of particles varying from powders to coarse lumps

ISO 5790:1979, Inorganic chemical products for industrial use – General method for determination of

chloride content – Mercurimetric method
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.

ISO and IEC maintain terminological databases for use in standardization at the following addresses:

• IEC Electropedia: available at http://www.electropedia.org/
• ISO Online browsing platform: available at http://www.iso.org/obp
3.1
laboratory sample

sample as prepared for sending to the laboratory and intended for inspection or testing

Note 1 to entry: in accordance with ISO 8213.
3.2
test sample

sample prepared from the laboratory sample and from which test portions will be taken

Note 1 to entry: in accordance with ISO 6206:1979.
3.3
test portion

quantity of material drawn from the test sample (or from the laboratory sample if both are the same) and

on which the test or observation is actually carried out
Note 1 to entry: in accordance with ISO 6206:1979.
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4 Methods of analysis

The methods to analyse the main product of standards EN 888, EN 889, EN 890, EN 891 and EN 14664

are listed in Table 1.

The methods to be used for analysis of iron-based coagulants and the principles of each method are listed

in Table 1 and described in full in Annex A (normative methods) and in Annex B (informative methods)

for analysis of iron content. The methods to be used for other parameters are listed in Table 2 and

described in Annexes C, D and E.
Table 1 — Determination of the iron content (normative and informative method)
Standard Main Test method annex and principle
number product

EN 888 Iron (III) A.3 Iron (III) chloride is determined as iron (III) content in the test

chloride sample. Iron (III) content is determined as the difference
B.2
between total iron content and iron (II) content.

EN 889 Iron (II) A.1 Iron (II) sulfate is determined as iron (II) content in the test

sulfate sample by titrimetry with cerium sulfate solution.
B.1

EN 890 Iron (III) A.3 Iron (III) sulfate is determined as iron (III) content in the test

sulfate, sample. Iron (III) content is determined as the difference
B.2
solution between total iron content and iron (II) content.

EN 891 Iron (III) A.3 Iron (III) chloride sulfate is determined as iron (III) content in

chloride the test sample. Iron (III) content is determined as the difference
B.2
sulfate between total iron content and iron (II) content.

EN 14664 Iron (III) A.3 Iron (III) sulfate is determined as iron (III) content in the test

sulfate, solid sample. Iron (III) content is determined as the difference
B.2
between total iron content and iron (II) content.

NOTE 1 An alternative method for determination of iron (II) and iron (III) content is described in Annex B.

Table 2 — Determination of parameters (normative and informative methods)
Parameter EN 888 EN 889 EN 890 EN 891 EN 14664 Method Principle
Insoluble X X X X X C.2 Weighted mass of the filtered
matters sample
Iron (II) X X X X A.1 Determination of iron (II) by
titration against cerium sulfate
B.1
Determination of iron (II) by
titration against potassium
dichromate
Free acid X X X X C.1 Titration with sodium hydroxide
Antimony X X X X X C.4 hydride generation atomic
absorption spectrometry
ICP/OES
ICP/MS
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EN 17215:2019 (E)
Parameter EN 888 EN 889 EN 890 EN 891 EN 14664 Method Principle
Arsenic X X X X X C.4 hydride generation atomic
absorption spectrometry
ICP/OES
ICP/MS
Cadmium X X X X X C.6 graphite furnace atomic
absorption spectrometry
ICP/OES
ICP/MS
Chromium X X X X X C.6 graphite furnace atomic
absorption spectrometry
ICP/OES
Manganese X X X X X C.3 flame atomic absorption
spectrometry (FAAS)
ICP-OES
ICP-MS
Mercury X X X X X C.5 cold vapour atomic absorption
spectrometry
Lead X X X X X C.6 graphite furnace atomic
absorption spectrometry
ICP/OES
ICP/MS
Nickel X X X X X C.6 graphite furnace atomic
absorption spectrometry
ICP/OES
Selenium X X X X X C.4 hydride generation atomic
absorption spectrometry
ICP/OES
ICP/MS

NOTE 2 An alternative method for determination of arsenic, antimony, cadmium, lead and selenium with the ICP

mass spectrometry is described in Annex E. An alternative method for analysis on arsenic, antimony, cadmium,

chromium, manganese, nickel, lead and selenium with the ICP/OES is described in Annex D.

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5 Sampling
5.1 General
Observe the general recommendations in ISO 3165 and take into account ISO 6206.
5.2 Solids

Prepare the laboratory sample required by the relevant procedure described in ISO 8213.

5.3 Solutions
5.3.1 Sampling from drums and bottles
5.3.1.1 General

Mix the contents of each container to be sampled by shaking the container, by rolling it or by rocking it

from side to side, taking care not to damage the container or spill any of the liquid.

If the design of the container is such (for example, a narrow-necked bottle) that it is impracticable to use

a sampling implement, take a sample by pouring after the contents have been thoroughly mixed.

Otherwise, proceed as described in 5.3.1.3.

Examine the surface of the liquid. If there are signs of surface contamination, take samples from the

surface as described in 5.3.1.2. Otherwise, take samples as described in 5.3.1.3.

5.3.1.2 Surface sampling

Take a sample using a suitable ladle. Lower the ladle into the liquid until the rim is just below the surface,

so that the surface layer runs into it. Withdraw the ladle just before it fills completely and allow any liquid

adhering to the ladle to drain off. If necessary, repeat this operation so that, when the other selected

containers have been sampled in a similar manner, the total volume of sample required for subsequent

analysis is obtained.
5.3.1.3 Bottom sampling

Take a sample using an open sampling tube, or a bottom-valve sampling tube, suited to the size of

container and the viscosity of the liquid.

When using an open sampling tube, close it at the top and then lower the bottom end to the bottom of the

container. Open the tube and move it rapidly so that the bottom of the tube traverses the bottom of the

container before the tube is filled. Close the tube, withdraw it from the container and allow any liquid

adhering at the outside of the tube to drain off.

When using a bottom-valve sampling tube, close the valve before lowering the tube into the container

and then proceed in a similar manner to that when using an open sampling tube.
5.3.2 Sampling from tanks and tankers
A representative sample should be taken as appropriate:
a) from the surface of the liquid, using a ladle as described in 5.3.1.2;

b) from the bottom of the tank or tanker, using a sampling tube as described in 5.3.1.3 or using specially

designed bottom-sampling apparatus;

c) from one or more positions, depending on the overall depth, between the bottom and the surface

using a weighted sampling can.
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6 Expression of results
6.1 Iron content

The iron content shall be expressed as iron (II) or iron (III) mass fraction in %.

6.2 Free acid
Free acid shall be expressed as mass fraction in %.
6.3 Insoluble matters
Insoluble matters shall be expressed as mass fraction in %.
6.4 Impurities
Impurities shall be expressed as mg/kg.
6.5 Repeatability

Each laboratory shall calculate the repeatability of the method under their laboratory conditions

according to the procedure.
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Annex A
(normative)
Analysis of the iron content

NOTE The strengths of iron salt solutions are measured on the basis of the iron (II) and iron (III) concentration

alone.
A.1 Determination of iron (II) concentration by titration against cerium (IV)
sulfate
A.1.1 General

This method applies to products with iron contents greater than a mass fraction of 0,2 %.

A.1.2 Principle

Iron (II) is directly titrated with cerium (IV) sulfate solution, which oxidises it to iron (III).

A.1.3 Reagents

All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 in

accordance with EN ISO 3696.
A.1.3.1 Hydrochloric acid solution (HCl) 5,0 mol/l

A.1.3.2 1,10-Phenanthroline ferrous complex solution (ferroin, ferrous indicator) ([Fe(o-

phen) ]SO ) 0,025 mol/l
3 4

A.1.3.3 Cerium (IV) sulfate solution, in 10 % w/v sulfuric acid, (Ce(SO ) ) 0,1 mol/l

4 2
A.1.4 Apparatus
Ordinary laboratory apparatus and glassware.
A.1.5 Procedure
A.1.5.1 Test solution

Weigh to the nearest 0,01 g, between 5 g and 10 g (m) of the laboratory sample and transfer to a conical

flask. Dilute with 50 ml ± 5 ml of water.
A.1.5.2 Determination

With mixing, add 0,5 ml of hydrochloric acid (A.1.3.1) to the conical flask. A clear deep yellow solution is

formed.

Add 2 to 4 drops (only) of the ferrous indicator (A.1.3.2). The solution will turn red.

Titrate the solution with cerium (IV) sulfate solution (A.1.3.3) from a volumetric burette. The end point

is achieved when a colour change from red to blue-green occurs and is sharp. Record the volume (V) of

cerium (IV) sulfate required for the titration.
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A.1.6 Calculation and expression of results

The iron (II) content, C , expressed as mass fraction in %, is given by the following formula:

(II)
V× 0,5585
C = (A.1)
(II)
where

V is the volume, in millilitres, of cerium (IV) sulfate required for the titration;

m is the mass, in grams, of the sample used for the test solution.
A.2 Determination of total iron
A.2.1 General
This method applies to the products at the supply concentration.
A.2.2 Principle

Iron is reduced by tin (II) chloride and is subsequently titrated with cerium (IV) sulfate.

A.2.3 Reagents

All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 in

accordance with EN ISO 3696.
A.2.3.1 Hydrochloric acid, HCl concentrated 1,19 g/ml
A.2.3.2 Tin (II) chloride solution (SnCl · 2H O) 0,5 mol/l
2 2

Dissolve 22,6 g of SnCl · 2H O with 20 ml of hydrochloric acid (A.2.3.1) and dilute with water to 200 ml.

2 2
Keep this solution in the dark.
A.2.3.3 Mercury (II) chloride, saturated solution (HgCl ) 0,27 mol/l

A.2.3.4 1,10-Phenanthroline ferrous complex solution (ferroin, ferrous indicator) ([Fe(o-

phen) ]SO ) 0,025 mol/l
3 4
A.2.3.5 Cerium (IV) sulfate (Ce(SO ) ) 0,1 mol/l
4 2
A.2.4 Apparatus
Ordinary laboratory apparatus and glassware.
A.2.5 Procedure
A.2.5.1 Test solution

Weigh to the nearest 0,01 g, between 5 g and 10 g of the laboratory sample (m) and transfer to a 200 ml

volumetric flask, dilute to the mark with water. Pipette 10 ml ± 0,2 ml of this solution into a 500 ml

conical flask.
A.2.5.2 Determination

Add 3 to 4 drops of hydrochloric acid (A.2.3.1) and heat until boiling while stirring.

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EN 17215:2019 (E)

Add drop by drop tin (II) chloride solution (A.2.3.2) until discoloration. (Reduction shall be achieved with

great care. Two drops of tin (II) chloride (A.2.3.2) are necessary, more shall be avoided.)

Cool the solution rapidly in cool water. Add 10 ml ± 0,2 ml of mercury (II) chloride (A.2.3.3). Dilute to

200 ml ± 5 ml with water and wait 3 min. A slight white cloud will appear regarding to mercury (II)

chloride addition. If a precipitate appears, stop the titration and reduce another aliquot of the laboratory

sample. Add 2 ml ± 0,2 ml of concentrated hydrochloric acid (A.2.3.1) and 4 to 6 drops of ferroin indicator

solution (A.2.3.4).
NOTE An alternative reduction method is given in Annex B.

Titrate the solution with cerium (IV) sulfate (A.2.3.5) from a volumetric burette. The end point is achieved

when a colour change from red to blue/green occurs. Record the volume (V) of cerium (IV) sulfate

required for the titration.

SAFETY PRECAUTIONS — Collect the residual solutions obtained from titrations and treat them in

accordance with Annex B of ISO 5790:1979, in order to prevent pollution of waste water.

A.2.6 Calculation and expression of results

The total iron content, C , expressed as mass fraction in %, is given by the following formula:

tot
V × 11,17
(A.2)
C =
tot
where

V is the volume, in millilitres, of cerium (IV) sulfate required for the titration;

m is the mass, in grams, of the sample used for the test solution.
A.3 Determination of iron (III)

The iron (III) content, C , expressed as mass fraction in %, is given by the following formula:

(III)
C C−C (A.3)
tot
III II
( ) ( )
where
C is the total iron content (A.2), expressed as mass fraction in %;
tot
C is the iron (II) content (A.1), expressed as mass fraction in %.
(II)
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Annex B
(informative)
Alternative analysis of the iron content
B.1 Determination of iron (II) concentration by titration against potassium
dichromate
B.1.1 General

This method applies to product with iron contents greater than a mass fraction of 0,2 %.

B.1.2 Principle
Iron is directly titrated with potassium dichromate solution.
B.1.3 Reagents

All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 in

accordance with EN ISO 3696.
B.1.3.1 Sulfuric acid, H SO concentrated 1,84 g/ml
2 4
B.1.3.2 Phosphoric acid, H PO concentrated 1,71 g/ml
3 4
B.1.3.3 Barium diphenylamine sulfonate solution (Ba(C H -NH-C H SO ) ) 8 mmol/l
6 5 6 4 3 2
B.1.3.4 Potassium dichromate solution (K Cr O ) 0,0166 mol/l
2 2 7
B.1.4 Apparatus
Ordinary laboratory apparatus and glassware.
B.1.5 Procedure
B.1.5.1 Test solution

Into a 500 ml conical flask, pour 200 ml ± 10 ml of water, 10 ml ± 1 ml of sulfuric acid (B.1.3.1) and

10 ml ± 1 ml of phosphoric acid (B.1.3.2). Cool with water. Weigh to the nearest 0,1 mg, between 3 g and

10 g of the laboratory sample and transfer to the conical flask containing the acid solution.

B.1.5.2 Determination

Titrate the test solution with potassium dichromate solution (B.1.3.4) with a volumetric burette and add

five drops of barium diphenylamine sulfonate (B.1.3.3) near the end-point.

End-point is achieved when a persistent purple colour appears, record the volume (V) of potassium

dichromate solution required for the complete titration.
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B.1.6 Calculation and expression of results

The iron (II) content, C , expressed as mass fraction in %, is given by the following formula:

(II)
V× 0,5585
C = (B.1)
(II)
where

V is the volume, in millilitres, of potassium dichromate required for the titration;

m is the mass, in grams, of the sample used for the test solution.
B.2 Determination of iron (III) concentration by iodometric titration
B.2.1 General

This method applies to products with iron contents greater than a mass fraction of 0,2 %.

B.2.2 Principle

Iron (III) oxidises iodide ions to iodine, which is titrated with sodium thiosulfate solution.

3+ - 2+
2Fe + 2I → 2Fe + I
2- - 2-
I + 2S O → 2I + S O .
2 2 3 4 6
B.2.3 Reagents

All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 in

accordance with EN ISO 3696.
B.2.3.1 Sodium thiosulfate solution (Na S O ) 0,1 mol/l
2 2 3
B.2.3.2 Potassium iodide, solid
B.2.3.3 Iodine indicator (starch), solid
B.2.3.4 Hydrochloric acid solution (HCl) 5,0 mol/l
B.2.4 Apparatus
Ordinary laboratory apparatus and glassware.
B.2.5 Procedure
B.2.5.1 Test solution

Weigh to the nearest 0,01 g, between 10 g and 20 g of sample (m) into a 250 ml volumetric flask, and

dilute to the mark with water. Transfer 20 ml ± 0,2 ml of the diluted solution to a 500 ml conical flask.

Add approximately 200 ml of water.
B.2.5.2 Determination
Add 20 ml ± 2 ml of hydrochloric acid (B.2.3.4).
Add 5 g ± 0,5 g of potassium iodide (B.2.3.2).
Mix the solution and allow the solution to stand in darkness for 5 min.
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