SIST EN 891:2005

SLOVENSKI STANDARD
SIST EN 891:2005
01-marec-2005
1DGRPHãþD
SIST EN 891:2000
Kemikalije, ki se uporabljajo za pripravo pitne vode - Železov (III) klorid sulfat
Chemicals used for treatment of water intended for human consumption - Iron (III)
chloride sulfate
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch - Eisen (III)
chloridsulfat
Produits chimiques utilisés pour le traitement de l'eau destinée a la consommation
humaine - Chlorosulfate de fer (III)
Ta slovenski standard je istoveten z: EN 891:2004
ICS:
13.060.20 Pitna voda Drinking water
71.100.80 .HPLNDOLMH]DþLãþHQMHYRGH Chemicals for purification of
water
SIST EN 891:2005 en
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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SIST EN 891:2005

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SIST EN 891:2005



EUROPEAN STANDARD
EN 891

NORME EUROPÉENNE

EUROPÄISCHE NORM
November 2004
ICS 71.100.80 Supersedes EN 891:1998
English version
Chemicals used for treatment of water intended for human
consumption - Iron (III) chloride sulfate
Produits chimiques utilisés pour le traitement de l'eau Produkte zur Aufbereitung von Wasser für den
destinée à la consommation humaine - Chlorosulfate de fer menschlichen Gebrauch - Eisen (III) chloridsulfat
(III)
This European Standard was approved by CEN on 30 September 2004.

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 Central Secretariat 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 Central Secretariat has the same status as the official
versions.

CEN members are the national standards bodies of Austria, Belgium, Cyprus, Czech Republic, Denmark, Estonia, Finland, France,
Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta, Netherlands, Norway, Poland, Portugal, Slovakia,
Slovenia, Spain, Sweden, Switzerland and United Kingdom.




EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

Management Centre: rue de Stassart, 36  B-1050 Brussels
© 2004 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 891:2004: E
worldwide for CEN national Members.

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SIST EN 891:2005
EN 891:2004 (E)
Contents
Page
Foreword.3
Introduction .4
1 Scope .5
2 Normative references .5
3 Description .5
4 Purity criteria.7
5 Test methods.9
6 Labelling - Transportation - Storage.12
Annex A (informative) General information on iron (III) chloride sulfate.14
Annex B (normative) Analytical methods .18
Annex C (informative) Reduction of Fe (III) on a silver column.33
Annex D (informative) Determination of cadmium, chromium, nickel and lead (inductively coupled
plasma optical emission spectrometry (ICP/OES)).34
Annex E (normative) General rules relating to safety.36
Bibliography .37

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SIST EN 891:2005
EN 891:2004 (E)
Foreword
This document (EN 891:2004) 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 May 2005, and conflicting national standards shall be withdrawn at the latest by
May 2005.
This document supersedes EN 891:1998.
Significant technical differences between this edition and EN 891:1998 are as follows:
a) replacement of the reference to EU Directive 80/778/ of 15 July 1980 with the latest Directive in force (see[1]) ;
b) expansion of annex A by addition of A.2 "Quality of commercial product" ;
c) deletion of annex F.
According to the CEN/CENELEC Internal Regulations, the national standards organizations of the following
countries are bound to implement this European Standard: Austria, Belgium, Cyprus, Czech Republic, Denmark,
Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Netherlands, Norway, Poland, Portugal, Slovakia, Slovenia, Spain, Sweden, Switzerland and United Kingdom.

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SIST EN 891:2005
EN 891:2004 (E)
Introduction
In respect of potential adverse effects on the quality of water intended for human consumption, caused by the
product covered by this document:
a) this document provides no information as to whether the product may be used without restriction in any of the
Member States of the EU or EFTA ;
b) it should be noted that, while awaiting the adoption of verifiable European criteria, existing national regulations
concerning the use and/or the characteristics of this product remain in force.
NOTE Conformity with this standard does not confer or imply acceptance or approval of the product in any of the Member
States of the EU or EFTA. The use of the product covered by this document is subject to regulation or control by National
Authorities.

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SIST EN 891:2005
EN 891:2004 (E)
1 Scope
This document is applicable to iron (III) chloride sulfate used for treatment of water intended for human
consumption. It describes the characteristics of iron (III) sulfate and specifies the requirements and the
corresponding analytical methods for iron (III) chloride sulfate (analytical methods are given in Annex B) and gives
information on its use in water treatment. It also determines the rules relating to safe handling and use of iron (III)
chloride sulfate (see annex E).

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 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 5790:1979, Inorganic chemical products for industrial use - General method for determination of chloride
content - Mercurimetric method.
ISO 6206, Chemical products for industrial use - Sampling – Vocabulary.
3 Description
3.1 Identification
3.1.1 Chemical name
Iron (III) chloride sulfate.
3.1.2 Synonym or common names
Ferric chloride sulfate, ferric chloro sulfate, chlorinated copperas.
3.1.3 Relative molecular mass
187,36.
3.1.4 Empirical formula
FeClSO .
4
3.1.5 Chemical formula
FeClSO .
4
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SIST EN 891:2005
EN 891:2004 (E)
1)
3.1.6 CAS Registry Number
12410-14-9.
2)
3.1.7 EINECS reference
235-649-0.
3.2 Commercial form
Iron (III) chloride sulfate is available as solution.
3.3 Physical properties
3.3.1 Appearance
Iron (III) chloride sulfate is a dark brown solution.
3.3.2 Density
The density of iron (III) chloride sulfate is approximately 1,5 g/ml.
3.3.3 Solubility (in water)
Iron (III) chloride sulfate is miscible in water.
NOTE Diluted solutions can hydrolyse and form a precipitate (see A.3.2).
3.3.4 Vapour pressure
Not applicable.
3)
3.3.5 Boiling point at 100 kPa
102 °C.
3.3.6 Freezing point
For the iron (III) chloride sulfate the freezing starts at approximately - 50 °C.
Below – 15 °C, sharp increase in viscosity.
3.3.7 Specific heat
Not known.
3.3.8 Viscosity (dynamic)
For the iron (III) chloride sulfate the viscosity is approximately 70 mPa.s at 10 °C.

1) Chemical Abstracts Service Registry Number.
2) European Inventory of Existing Commercial Chemical Substances.
3) 100 kPa = 1 bar.
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3.3.9 Critical temperature
Not applicable.
3.3.10 Critical pressure
Not applicable.
3.3.11 Physical hardness
Not applicable.
3.4 Chemical properties
The solutions of iron (III) chloride sulfate are acidic and highly corrosive.
4 Purity criteria
4.1 General
This document specifies the minimum purity requirements for iron (III) chloride sulfate used for the treatment of
water intended for human consumption. Limits are given for impurities commonly present in the product.
Depending on the raw material and the manufacturing process other impurities may be present and, if so, this shall
be notified to the user and when necessary to relevant authorities.
NOTE Users of this product should check the national regulations in order to clarify whether it is of appropriate purity for
treatment of water intended for human consumption, taking into account raw water quality, required dosage, contents of other
impurities and additives used in the product not stated in this product standard.
Limits have been given for impurities and chemical parameters where these are likely to be present in significant
quantities from the current production process and raw materials. If the production process or raw materials lead to
significant quantities of impurities, by-products, or additives being present, this shall be notified to the user.
4.2 Composition of commercial product
The product shall contain not less than a mass fraction of 36,9 % of FeClSO (i.e. not less than a mass fraction of
4
11 % of Fe) and shall be within ± 3 % of the manufacturer's declared values.
4.3 Impurities and main by-products
The product shall conform to the requirements specified in Table 1.
The concentration limits refer to Fe (III).
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SIST EN 891:2005
EN 891:2004 (E)
Table 1 — Impurities
Impurity Limit
Mass fraction of Fe (III) content
in %
Grade 1 Grade 2 Grade 3
Manganese max. 0,5 1 2
a
max. 2,5 2,5 2,5
Iron(II)
b
max. 0,2 0,2 0,2
Insoluble matters
a
Fe (II) has a lower coagulant efficiency compared to Fe (III).
Also hydrolysis of Fe (II) starts at pH value 8, and therefore Fe (II) can remain into the
water at lower pH values.
b
An excess of insoluble matters indicates the presence of foreign matter. Iron is a
component of the product will usually be removed in the treatment process.
4.4 Chemical parameters
The product shall conform to the requirements specified in Table 2.
The concentration limits are specified in milligrams per kilogram of Fe (III).
Table 2 — Chemical parameters
Parameter Limit in mg/kg of Fe (III)
Type 1 Type 2 Type 3
Arsenic (As) max. 1 20 50
Cadmium (Cd) max. 1 25 50
Chromium (Cr) max. 100 350 500
Mercury (Hg) max. 0,1 5 10
Nickel (Ni) max. 300 350 500
Lead (Pb) max. 10 100 400
Antimony (Sb) max. 10 20 60
Selenium (Se) max. 1 20 60
-
NOTE Cyanide (CN ), pesticides and polycyclic aromatic hydrocarbons are
not relevant since the raw materials used in the manufacturing process are free of
them. For maximum impact of iron (III) chloride sulfate on trace metal content in
drinking water see A.2.
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5 Test methods
5.1 Sampling
5.1.1 General
Observe the general recommendations in ISO 3165 and take into account ISO 6206.
Prepare the laboratory sample required by the relevant procedure described in 5.1.2 and 5.1.3.
5.1.2 Sampling from drums and bottles
5.1.2.1 General
5.1.2.1.1 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.
5.1.2.1.2 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 5.1.2.3.
5.1.2.1.3 Examine the surface of the liquid. If there are signs of surface contamination, take samples from the
surface as described in 5.1.2.2. Otherwise, take samples as described in 5.1.2.3.
5.1.2.2 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.
5.1.2.3 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.
5.1.3 Sampling from tanks and tankers
From each access point, take samples as follows:
a) from the surface of the liquid, using a ladle as described in 5.1.2.2 ;
b) from the bottom of the tank or tanker, using a sampling tube as described in 5.1.2.3 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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5.2 Analyses
5.2.1 Main product
Iron (III) chloride sulfate is determined as Fe (III) content in the test sample. Fe (III) content is determined as the
difference between total iron content and Fe (II) content (see B.1).
5.2.2 Impurities
5.2.2.1 Manganese
The manganese content shall be determined by flame atomic absorption spectrometry (FAAS) (see B.2).
5.2.2.2 Iron (II) : Fe (II)
The iron (II) content is expressed as C (see B.1.2.5.3).
(II)
5.2.2.3 Insoluble matters
The mass fraction of the insoluble matters shall be determined in accordance with the method described in B.3.
5.2.3 Chemical parameters
5.2.3.1 Preparation of sample solution
5.2.3.1.1 General
Oxidation and wet digestion is used to bring the samples into a stable solution.
5.2.3.1.2 Principle
)
Oxidation with hydrogen peroxide (H O followed by digestion with hydrochloric acid (HCl).
2 2
5.2.3.1.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 specified in
EN ISO 3696.
5.2.3.1.3.1 Hydrochloric acid (HCl), solution, mass fraction 30 %.
5.2.3.1.3.2 Hydrogen peroxide (H O ), solution, mass fraction 30 %.
2 2
5.2.3.1.4 Apparatus
Ordinary laboratory apparatus and glassware together with the following.
5.2.3.1.4.1 Analytical balance
5.2.3.1.4.2 Graduated cylinder, capacity 50 ml.
5.2.3.1.4.3 Round flask with reflux condenser.
5.2.3.1.4.4 Hot plate.
5.2.3.1.4.5 Volumetric flask, capacity 200 ml.
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5.2.3.1.5 Procedure
Dissolve with 20 ml of water 20,0 g of the iron solution. Add 5 ml hydrogen peroxide solution (5.2.3.1.3.2) to iron
(III)-samples. After adding 50 ml hydrochloric acid (5.2.3.1.3.1) boil the solution for 15 min by using a reflux
condenser (5.2.3.1.4.3). Cool down the solution, transfer to a 200 ml volumetric flask (5.2.3.1.4.5) and fill up to the
mark with water. This is the sample solution.
5.2.3.2 Arsenic
The arsenic content shall be determined by hydride generation atomic absorption spectrometry (see B.4).
5.2.3.3 Cadmium
The cadmium content shall be determined by graphite furnace atomic absorption spectrometry (see B.6).
5.2.3.4 Chromium
The chromium content shall be determined by graphite furnace atomic absorption spectrometry (see B.6).
5.2.3.5 Mercury
The mercury content shall be determined by cold vapour atomic absorption spectrometry (see B.5).
5.2.3.6 Nickel
The nickel content shall be determined by graphite furnace atomic absorption spectrometry (see B.6).
5.2.3.7 Lead
The lead content shall be determined by graphite furnace atomic absorption spectrometry (see B.6).
5.2.3.8 Antimony
The antimony content shall be determined by hydride generation atomic absorption spectrometry (see B.4).
5.2.3.9 Selenium
The selenium content shall be determined by hydride generation atomic absorption spectrometry (see B.4).
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EN 891:2004 (E)
6 Labelling - Transportation - Storage
6.1 Means of delivery
In order that the purity of the product is not affected, the means of delivery shall not have been used previously for
any different product or it shall have been specially cleaned and prepared before use.
4)
6.2 Risk and safety labelling according to the EU Directives
The following labelling requirements shall apply to iron (III) chloride sulfate at the date of the publication of this
document.
 Symbols and indications of danger :
C: Corrosive.
 Nature of special risks attributed to dangerous substances :
R 21/22 : Harmful in contact with skin and if swallowed ;
R 34 : Causes burns ;
R 36/38 : Irritating to eyes and skin.
 Safety advice concerning dangerous substances :
S 24/25 : Avoid contact with skin and eyes ;
S 37/39 : Wear suitable gloves and eye/face protection.
NOTE Annex I of the Directive 67/548/EEC on Classification, packaging and labelling of dangerous substances and its
amendments and adaptations in the European Union contains a list of substances classified by the EU. Substances not in this
Annex I should be classified on the basis of their intrinsic properties according to the criteria in the Directive by the person
responsible for the marketing of the substance.
6.3 Transportation regulations and labelling
5)
Iron (III) chloride sulfate is listed as UN Number , 2582.
6) 7)
RID ADR : Class 8, classification code C1; packing group III;
8)
IMDG : Class 8.
9)
IATA : Class 8.

4) See [2].
5) United Nations Number.
6) Regulations concerning International carriage of Dangerous goods by rail.
7) European Agreement concerning the international carriage of Dangerous goods by Road.
8) International Maritime transport of Dangerous Goods.
9) International Air Transport Association.
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SIST EN 891:2005
EN 891:2004 (E)
6.4 Marking
The marking shall include the following information :
 the name "iron(III) chloride sulfate", trade name, grade and type ;
 the net mass ;
 the name and the address of the supplier and/or manufacturer ;
 the statement "this product conforms to EN 891".
6.5 Storage
6.5.1 Long term stability
Unlimited storage in plastics or rubber lined containers or tanks.
NOTE Some sedimentation of yellow iron (III) chloride sulfate can occur.
6.5.2 Storage incompatibilities
Iron (III) chloride sulfate has a highly acid and corrosive character. Avoid any contact with metals. Keep away from
alkaline agents. Avoid contact with agents capable of liberating chlorine.
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SIST EN 891:2005
EN 891:2004 (E)
Annex A
(informative)

General information on iron (III) chloride sulfate
A.1 Origin
A.1.1 Raw materials
The product is manufactured from iron (II) sulfate and chlorine.
A.1.2 Manufacturing process
Iron (III) chloride sulfate is product by dissolving iron (II) sulfate in water in treating with gaseous chlorine
A.2 Quality of commercial product
The three types of iron (III) chloride sulfate specified in Table 2 reflect the quality of commercially available
products. Figures A.1 to A.3 show the maximum concentrations of trace metals that would be added to the raw
water by the addition of products corresponding to the purity levels specified in Table 2. It can be seen that the
concentrations of metal added are well below the Parametric Values given in the EU Directive 98/83/EC (see [1]) at
typical product doses. Furthermore, the figures overstate the concentrations of metals that would be present in the
treated water since a substantial proportion of the trace metals will be incorporated in the sludge. Users of this
product should select an appropriate grade and type to enable them to achieve treated water quality targets taking
into account raw water characteristics, required dosage, process plant conditions and other relevant factors.


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SIST EN 891:2005
EN 891:2004 (E)

Key
1 Maximum addition to water µg/l metal
2 Product dosage mg/l Fe - Typical dose
A Element
B Drinking water limit µg/l

Figure A.1 — Maximum impact of iron (III) chloride sulfate, type 1, on trace metal content of water

Key
1 Maximum addition to water µg/l metal
2 Product dosage mg/l Fe - Typical dose
A Element
B Drinking water limit µg/l

Figure A.2 — Maximum impact of iron (III) chloride sulfate, Type 2, on trace metal content of water
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EN 891:2004 (E)


Key
1 Maximum addition to water µg/l metal
2 Product dosage mg/l Fe- Typical dose
A Element
B Drinking water limit µg/l


Figure A.3 — Maximum impact of iron (III) chloride sulfate, Type 3, on trace metal content of water
A.3 Use
A.3.1 Function
The product is used as primary coagulant.
A.3.2 Form in which it is used
The product of a mass fraction of 40 % is used as delivered or diluted (see 3.3.3). Solutions with a concentration
less than a mass fraction of 1 % can hydrolyse and form a precipitate.
A.3.3 Treatment dose
3
The treatment dose is variable depending on raw water quality and corresponds to approximately 30 g/m to
3 3 3
75 g/m (corresponding to a treatment dose between 4 g/m and 10 g/m expressed as Fe).
A.3.4 Means of application
The product can be dosed as delivered by acid resistant pumps. To promote a rapid dispersion a high turbulence at
the point of addition and dilution with carrier water is desirable.
A.3.5 Secondary effects
Increase of the chloride and sulfate content. Reduction of alkalinity and pH value.
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A.3.6 Removal of excess product
The coagulation process includes the hydrolysis of the ferric ions to ferric hydroxide. This precipitate is removed by
sedimentation, flotation and/or filtration.
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Annex B
(normative)

Analytical methods
B.1 Determination of iron(III) chloride sulfate
B.1.1 Total iron
B.1.1.1 General
This method applies to products with iron contents greater than of a mass fraction of 0,2 %.
B.1.1.2 Principle
Iron is reduced by tin (II) chloride and is subsequently titrated with potassium dichromate solution.
B.1.1.3 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.1.1.3.1 Hydrochloric acid, HCl concentrated, density ρ = 1,19 g/ml.
B.1.1.3.2 Tin (II) chloride solution, c(SnCl .2H O) = 0,5 mol/l. Dissolve 22,6 g of SnCl . 2H O with 20 ml of
2 2 2 2
hydrochloric acid (B.1.1.3.1) and dilute with water to 200 ml. Keep this solution in the dark.
B.1.1.3.3 Mercury (II) chloride, saturated solution c(HgCl ) = 0,27 mol/l.
2
B.1.1.3.4 Sulfuric acid, H SO concentrated, density ρ = 1,84 g/ml.
2 4
B.1.1.3.5 Phosphoric acid, H PO concentrated, density ρ = 1,71 g/ml.
3 4
B.1.1.3.6 Barium diphenylamine sulfonate solution, c(Ba(C H -NH-C H SO ) ) = 8 mmol/l.
6 5 6 4 3 2
B.1.1.3.7 Potassium dichromate solution, c(K Cr O ) = 0,0166 mol/l.
2 2 7
B.1.1.4 Apparatus
Ordinary laboratory apparatus and glassware.
B.1.1.5 Procedure
B.1.1.5.1 Test solution
Weigh to the nearest 0,1 mg, 10 g of the laboratory sample and transfer to a 200 ml volumetric flask, dilute to the
mark with water. Pipette 10 ml and transfer to a 500 ml conical flask.
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B.1.1.5.2 Determination
Add some drops of hydrochloric acid (B.1.1.3.1) and heat until boiling while stirring.
Add drop by drop tin (II) chloride solution (B.1.1.3.2) until discoloration. Reduction shall be achieved with great
care. Two drops of tin (II) chloride (B.1.1.3.2) are necessary, more shall be avoided.
Cool the solution rapidly in cool water.
Add 10 ml of mercury (II) chloride (B.1.1.3.3). Dilute to 200 ml 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 10 ml of sulfuric acid (B.1.1.3.4) and 10 ml of phosphoric acid (B.1.1.3.5).
NOTE An alternative reduction method is given in annex C.
Titrate the test solution with potassium dichromate (B.1.1.3.7) with a volumetric burette and add five drops of
barium diphenylamine sulfonate (B.1.1.3.6) near the end-point.
End-point is achieved when a persistent purple colour appears. Record the volume (V) of potassium dichromate
required for the complete 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.
B.1.1.5.3 Expression of results
The total iron content, C expressed as mass fraction , is given by the following equation :
tot
V ×11,16
C = (1)
tot
m
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.1.2 Determination of iron(II) : Fe(II)
B.1.2.1 General
This method applies to products with iron contents greater than of a mass fraction of 0,2 %.
B.1.2.2 Principle
Iron is directly titrated with potassium dichromate solution.
B.1.2.3 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.1.2.3.1 Sulfuric acid, H SO concentrated, density ρ = 1,84 g/ml.
2 4
B.1.2.3.2 Phosphoric acid, H PO concentrated, density ρ = 1,71 g/ml.
3 4
B.1.2.3.3 Barium diphenylamine sulfonate solution, c(Ba(C H -NH-C H SO ) ) = 8 mmol/l.
6 5 6 4 3 2
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B.1.2.3.4 Potassium dichromate solution, c(K Cr O ) = 0,0166 mol/l.
2 2 7
B.1.2.4 Apparatus
Ordinary laboratory apparatus and glassware.
B.1.2.5 Procedure
B.1.2.5.1 Test solution
In a 500 ml conical flask, pour 200 ml of water, add 10 ml of sulfuric acid (B.1.2.3.1) and 10 ml of phosphoric acid
(B.1.2.3.2). Cool with water. Weigh to the nearest 0,1 mg, between 3 g and 10 g of the laboratory sample and
transfer into the conical flask containing the acid solution.
B.1.2.5.2 Determination
Titrate the test solution with potassium dichromate (B.1.2.3.4) with a volumetric burette and add five drops of
barium diphenylamine sulfonate (B.1.2.3.3) near the end-point.
End-point is achieved when a persistent purple colour appears, record the volume (V) of potassium dichromate
required for the complete titration.
B.1.2.5.3
...