SIST EN 901:2025

SLOVENSKI STANDARD
01-marec-2025
Nadomešča:
SIST EN 901:2013
Kemikalije, ki se uporabljajo za pripravo pitne vode - Natrijev hipoklorit
Chemicals used for treatment of water intended for human consumption - Sodium
hypochlorite
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch -
Natriumhypochlorit
Produits chimiques utilisés pour le traitement de l'eau destinée à la consommation
humaine - Hypochlorite de sodium
Ta slovenski standard je istoveten z: EN 901:2024
ICS:
13.060.20 Pitna voda Drinking water
71.100.80 Kemikalije za čiščenje vode Chemicals for purification of
water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

EN 901
EUROPEAN STANDARD
NORME EUROPÉENNE
December 2024
EUROPÄISCHE NORM
ICS 71.100.80 Supersedes EN 901:2013
English Version
Chemicals used for treatment of water intended for human
consumption - Sodium hypochlorite
Produits chimiques utilisés pour le traitement de l'eau Produkte zur Aufbereitung von Wasser für den
destinée à la consommation humaine - Hypochlorite de menschlichen Gebrauch - Natriumhypochlorit
sodium
This European Standard was approved by CEN on 18 November 2024.

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, 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.
EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Rue de la Science 23, B-1040 Brussels
© 2024 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 901:2024 E
worldwide for CEN national Members.

Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Terms and definitions . 6
4 Description . 6
4.1 Identification . 6
4.2 Commercial form . 7
4.3 Physical properties . 7
4.3.1 Appearance and odour . 7
4.3.2 Density . 7
4.3.3 Solubility in water . 7
4.3.4 Vapour pressure . 7
4.3.5 Boiling point at 100 kPa . 7
4.3.6 Crystallization and freezing point . 7
4.3.7 Specific heat . 7
4.3.8 Viscosity (dynamic) . 7
4.3.9 Critical temperature . 8
4.3.10 Critical pressure . 8
4.3.11 Physical hardness . 8
4.4 Chemical properties . 8
5 Purity criteria . 8
5.1 General. 8
5.2 Composition of commercial product . 8
5.3 Impurities and main by-products . 8
5.4 Chemical parameters. 9
6 Test methods . 9
6.1 Sampling . 9
6.2 Analysis . 10
6.2.1 Determination of available chlorine content (main product) . 10
6.2.2 Impurities . 12
6.2.3 Chemical parameters. 17
7 Labelling - transportation - storage . 19
7.1 Product labelling . 19
7.2 Labelling . 20
7.3 Storage . 21
7.3.1 General information . 21
7.3.2 Long term stability . 21
7.3.3 Impermissible storage conditions . 21
7.4 Transportation and labelling . 21
Annex A (informative) General information on sodium hypochlorite . 22
Annex B (informative) General rules relating to safety . 25
Annex C (normative) Determination of arsenic, antimony and selenium (atomic absorption
spectrometry hydride technique) . 26
Annex D (informative) Determination of bromate ion content in sodium hypochlorite by
liquid chromatography of ions and UV detection . 33
Annex E (informative) Results of inter-laboratory tests on sodium bromate determination
in sodium hypochlorite commercial solutions . 37
Bibliography . 38
European foreword
This document (EN 901:2024) 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 June 2025, and conflicting national standards shall be
withdrawn at the latest by June 2025.
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.
This document supersedes EN 901:2013.
a) modification of 6.3 on transportation regulations and labelling, adding the sentence “The user shall
be aware of the incompatibilities between transported products.”;
b) modification of 6.4 on marking, adding the note “at least the name and type of the product are clearly
marked or displayed at viewing height on the means of delivery”.
Any feedback and questions on this document should be directed to the users’ national standards body.
A complete listing of these bodies can be found on the CEN website.
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, 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 the United
Kingdom.
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 regarding whether the product may be used without
restriction in any of the Member States of the EU or EFTA;
b) 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 1 Conformity with this document does not confer or imply acceptance or approval of the product in any of
the Member States of the EU or EFTA. Use of the product covered by this document is subject to regulation or control
by National Authorities.
NOTE 2 This product is a biocide. At the time of publication, Regulation EU 528/2012 [1] on biocide is in force.
1 Scope
This document is applicable to sodium hypochlorite used for treatment of water intended for human
consumption. It describes the characteristics of sodium hypochlorite and specifies the requirements and
the corresponding test methods for sodium hypochlorite. It gives information on its use in water
treatment. It also determines the rules relating to safe handling and use of sodium hypochlorite (see
Annex B).
NOTE While this document is not applicable to sodium hypochlorite generated in situ (see bibliographic
reference [6]), the limits for impurities and chemical parameters apply.
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 1233, Water quality — Determination of chromium — Atomic absorption spectrometric methods
EN ISO 3696:1995, Water for analytical laboratory use — Specification and test methods (ISO 3696:1987)
EN ISO 12846, Water quality — Determination of mercury — Method using atomic absorption
spectrometry (AAS) with and without enrichment (ISO 12846)
ISO 3165, Sampling of chemical products for industrial use — Safety in sampling
ISO 6206, Chemical products for industrial use — Sampling — Vocabulary
ISO 8288:1986, Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame
atomic absorption spectrometric methods
3 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
ISO and IEC maintain terminology databases for use in standardization at the following addresses:
— ISO Online browsing platform: available at https://www.iso.org/obp
— IEC Electropedia: available at https://www.electropedia.org/
4 Description
4.1 Identification
4.1.1 Chemical name
Sodium hypochlorite.
4.1.2 Synonym or common names
Liquid bleach, soda bleach, bleach lye.
4.1.3 Relative molecular mass
74,44.
4.1.4 Empirical formula
NaClO.
4.1.5 Chemical formula
NaClO.
4.1.6 CAS Registry Number
7681-52-9.
4.1.7 EINECS reference
231-668-3.
4.2 Commercial form
The product is supplied as an aqueous solution with an available (active) chlorine concentration up to a
mass fraction of 18 %.
4.3 Physical properties
4.3.1 Appearance and odour
The concentrated products are a clear yellowish-green solution with a faint chlorinous odour, diluted
products are visually colourless.
4.3.2 Density
The density of the product varies between 1,13 g/ml and 1,30 g/ml at 20 °C.
4.3.3 Solubility in water
The product is capable of being mixed with water in any proportion.
4.3.4 Vapour pressure
Approximately 2,5 kPa at 20 °C.
4.3.5 Boiling point at 100 kPa
Not applicable.
4.3.6 Crystallization and freezing point
At about – 10 °C crystallization of NaOCl·6 H O starts from concentrated products.
Freezing of the concentrated product takes place between - 20 °C and - 30 °C.
4.3.7 Specific heat
The specific heat is 3,48 kJ/(kg.K) for a solution with an available active chlorine concentration of mass
fraction between 14 % and 15 %.
4.3.8 Viscosity (dynamic)
2,6 mPa.s at 20 °C.
Chemical Abstracts Service Registry Number.
European Inventory of Existing Commercial Chemical Substances.
100 kPa = 1 bar.
4.3.9 Critical temperature
Not applicable.
4.3.10 Critical pressure
Not applicable.
4.3.11 Physical hardness
Not applicable.
4.4 Chemical properties
The product is an alkaline solution with a pH value greater than 11 at 20 °C.
It reacts with acids and acidic salts to form chlorine.
Vigorous reactions occur with reducing chemicals.
-
It is a strong oxidant (E°Red for (ClO ) = 0,89 V at pH 14).
- + - -
ClO + 2 H +2 e → Cl + H O
5 Purity criteria
5.1 General
This document specifies the minimum purity requirements for sodium hypochlorite used for treating
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, the user, and when necessary the relevant authorities, shall be notified.
When evaluating appropriate purity for treating water intended for human consumption, users should
take into account raw water quality, required dosage, contents of other impurities and additives used in
the product that are not stated in this document.
NOTE Regarding purity for treating water intended for human consumption, local regulations and
requirements can apply.
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 the raw materials bring about the presence of significant amounts of impurities, by-products or
additives, the user shall be notified.
5.2 Composition of commercial product
Sodium hypochlorite is available only in solutions with concentrations up to 18 % active chlorine at the
time of delivery by the supplier. Common concentrated products contain a minimum of 12 % active
chlorine. Diluted solutions are also available.
The concentration of sodium hypochlorite shall be equal to or greater than the value specified by the
manufacturer.
5.3 Impurities and main by-products
The product contains sodium chloride (NaCl) in equimolar amounts at minimum, and a small portion of
sodium hydroxide (NaOH) which keeps the product alkaline. Thus, a little amount of sodium carbonate
CO ) can be present, too.
(Na2 3
The sodium chlorate (NaClO ) / chlorate (ClO ) content shall not exceed a mass fraction of 5,4 % / 4,22 %
3 3
of available chlorine at the time of delivery by the supplier.
Traces of sodium bromate (NaBrO ) can be present depending on the content of bromine in the raw
material chlorine.
The product shall be visibly free from deposits or suspended matter.
NOTE Sodium chlorate is a by-product of the manufacturing process and is also formed during transportation
and storage (see 7.3.2).
5.4 Chemical parameters
The product shall conform to the requirements specified in Table 1.
Table 1 — Chemical parameters
Parameter  Limit in mg/kg of available chlorine
Type 1 Type 2
Arsenic (As) max. 1 5
Antimony (Sb) max. 20 25
Cadmium (Cd) max. 2,5 5
Chromium (Cr) max. 2,5 5
Lead (Pb) max. 15 15
Mercury (Hg) max. 3,5 5
Nickel (Ni) max. 2,5 10
Selenium (Se) max. 20 25
Limit in g/kg of available chlorine
a
Sodium bromate max. 2,5 5,0
Limit in % of available chlorine
a
Sodium chlorate max. 5,4
a
Compound is a by-product of the manufacturing process.
NOTE Cyanide, which does not exist in a strong oxidising medium such as
sodium hypochlorite, is not a relevant chemical parameter. Pesticides and
polycyclic aromatic hydrocarbons are not by-products of the manufacturing
process. For parametric values of sodium hypochlorite on trace metal content
in drinking water, see bibliographic reference [2].
6 Test methods
6.1 Sampling
Observe the general recommendations of ISO 3165 and take account of ISO 6206.
6.2 Analysis
6.2.1 Determination of available chlorine content (main product)
6.2.1.1 General
This method applies to all commercial products with available chlorine contents within the range
of 70 g/l to 170 g/l.
NOTE It detects all oxidising agents being active in weak acidic solutions, i.e. hypochlorite/chlorine, iodate, and
partially chloramines, Fe(III), etc. Bromate and chlorate are not covered under these conditions.
6.2.1.2 Principle
Sodium hypochlorite reacts with potassium iodide to release iodine in the presence of acetic acid. The
iodine is titrated with sodium thiosulfate standard volumetric solution in the presence of starch indicator
solution.
The titration may also be carried out potentiometrically by the aid of titration automates, in which case
the addition of soluble starch is unnecessary.
6.2.1.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3, as
specified in EN ISO 3696:1995 (de-ionized water for common laboratory purposes).
6.2.1.3.1 Potassium iodide solution, mass fraction 10 %
Weigh, to the nearest 0,1 mg, 100 g of potassium iodide, iodate-free, and dissolve in water and dilute
to 1 l.
6.2.1.3.2 Acetic acid concentrated, of purity at least of mass fraction 99 %
6.2.1.3.3 Sodium thiosulfate standard volumetric solution, c(Na2S2O3·5H2O) = 0,1 mol/l
Standard volumetric solutions are commercially available, which might require dilution.
Alternatively, a standard volumetric solution may be prepared by the following procedure:
Dissolve 24,8 g Na S O ·5H O in a 1 000 ml one-mark volumetric flask in 0,75 l of water. After the
2 2 3 2
temperature has equalised, make up to the mark with water and mix thoroughly.
To standardize: Weigh, to the nearest 0,1 mg, 3,600 g (m) of dry potassium iodate. Dissolve in water in
a 1 000 ml one-mark volumetric flask, make up to the mark with water and mix (standard reference
solution c(1/6 KIO ) = 0,1 mol/l). Place 200 ml of water in a 500 ml stoppered conical flask, add (2 ± 0,5)
g of potassium iodide and stir to dissolve. Then introduce, by means of a pipette, 10,0 ml of sodium
thiosulfate solution for standardization, add (15 ± 1) ml of hydrochloric acid solution (diluted 1 + 1 by
volume) and (5 ± 1) ml of starch solution (6.2.1.3.4). Titrate immediately with the potassium iodate
standard reference solution until the appearance of a blue coloration that persists for 30 s. Record the
volume (V ) of iodate used.
The actual concentration, c, of the sodium thiosulfate standard volumetric solution (Na S O3·5H O),
2 2 2
expressed in moles per litre is given by Formula (1):
Vc×
c = (1)
V
where
c is the concentration, expressed in moles per litre, of the potassium iodate standard
reference solution [c(1/6 KIO ) = 0,1 mol/l ];
V is the volume, in millilitres, of the sodium thiosulfate standard volumetric solution used for
the standardization (V = 10 ml);
V is the volume, in millilitres, of potassium iodate standard reference solution used in the
titration.
6.2.1.3.4 Starch solution, mass fraction of 1 %
Make a slurry with (1 ± 0,1) g of starch and (5 ± 1) ml of water. Add (90 ± 5) ml of boiling water to the
slurry. Stir to dissolve it and cool the solution. This solution needs to be refrigerated to avoid the
decomposition of the starch which results in a vague end point. Keep the solution cool and use it within
one week.
Commercial indicators for iodine titration exist and may be used in place of the specified starch solution,
provided that their efficiency has been previously tested.
6.2.1.4 Apparatus
Ordinary laboratory apparatus and glassware.
6.2.1.5 Procedure
6.2.1.5.1 Test solution
Weigh to the nearest 0,1 mg 1 g of the laboratory sample (record mass m in grams) into a 250 ml conical
flask and dilute with water up to 100 ml.
6.2.1.5.2 Determination
Add 10 ml of the potassium iodide solution (6.2.1.3.1) and 5 ml of concentrated acetic acid (6.2.1.3.2).
Titrate at once with the sodium thiosulfate standard volumetric solution (6.2.1.3.3) until the iodine colour
is nearly gone. Add 3 ml of the starch indicator solution (6.2.1.3.4) and complete the titration until the
disappearance of the blue-black colour. Record the volume V , of the sodium thiosulfate standard
volumetric solution added.
6.2.1.6 Expression of results
The available chlorine (Cl ) content, w , expressed in mass fraction in %, is given by Formula (2):
2 2
w = (V × c × 3,545) / (m ) (2)
2 1 1
where
V is the volume, in millilitres, of the sodium thiosulfate standard volumetric solution
(6.2.1.3.3);
c is the concentration in moles per litre, of the sodium thiosulfate standard volumetric
solution (see 6.2.1.3.3);
3,545 is the mass in milligrams of chlorine (Cl ) corresponding to 1 ml of sodium thiosulfate
solution of c(Na S O .5H O) = 0,100 mol/l;
2 2 3 2
m is the mass in grams of the laboratory sample used to prepare the test solution
(6.2.1.5.1).
6.2.2 Impurities
6.2.2.1 Determination of sodium chlorate content (NaClO3)
6.2.2.1.1 General
This method is used to determine the chlorate content, in the range between 3,75 g/l and 15 g/l, in
sodium hypochlorite solutions for commercial use; it is specific for these species.
6.2.2.1.2 Principle
Direct determination of chlorate ions in a diluted solution of sodium hypochlorite by ion chromatography
with suppressed conductimetric detection.
6.2.2.1.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall have a conductivity
of 0,056 μS/cm (conform to grade 1, as specified in EN ISO 3696:1995).
6.2.2.1.3.1 Sodium carbonate and sodium hydrogen carbonate, eluant solution.
Mix one volume of sodium carbonate solution c(Na CO ) = 2 mmol/l with one volume of sodium
2 3
hydrogen carbonate solution c(NaHCO ) = 0,75 mmol/l.
6.2.2.1.3.2 Sulfuric acid solution c(H SO ) = 0,025 mol/l regenerant solution.
2 4
6.2.2.1.3.3 Helium gas, high purity, for degassing eluant and regenerant solutions.
6.2.2.1.3.4 Sodium chlorate stock solution 1 g/l.
. Dissolve in 200 ml of the water (grade 1,
Weigh, to the nearest 0,000 1 g, 0,255 1 g of NaClO3
EN ISO 3696:1995).
6.2.2.1.4 Apparatus
Ordinary laboratory apparatus and glassware, together with the following.
6.2.2.1.4.1 Ion chromatograph
6.2.2.1.4.2 Chemical suppressed conductivity detector
6.2.2.1.4.3 Anionic column and pre-column
Resin composed of 15 μm polystyrene/divinylbenzene substrate agglomerated with anion exchange
latex that has been aminated.
6.2.2.1.4.4 Data logger/plotter, able to record and display the chromatographic peak heights.
6.2.2.1.4.5 Generator of water (grade 1, EN ISO 3696:1995).
6.2.2.1.5 Chromatographic conditions
— Eluant flow rate: 2 ml/min;
— regenerant flow rate: 2,5 ml/min;
— full scale of conductivity: 30 mS;
— residual conductivity: < 18 mS.
6.2.2.1.6 Procedure
6.2.2.1.6.1 Preparation of calibration solutions
Prepare calibration solutions in volumetric flasks by diluting accurately measured volumes of the
chlorate stock solution (6.2.2.1.3.4) with the eluant solution (6.2.2.1.3.1), in accordance with Table 2.
Table 2 — Calibration solutions for determination of chlorate content
-
Solution ClO3 in mg/l NaClO3 in mg/l
1 3,75 4,78
2 7,5 9,57
3 11,25 14,35
4 15 19,13
NOTE Calibration is linear for concentration of chlorate ion between 3,75 mg/l and 15 mg/l in the diluted
solution.
6.2.2.1.6.2 Preparation of test solution
Weigh to the nearest 0,1 mg 250 mg of the laboratory sample (record mass m in milligrams) into
a 100,0 ml measuring flask, fill up with eluant solution (6.2.2.1.3.1) and homogenize the test solution by
shaking the sealed flask carefully.
6.2.2.1.6.3 Measurement of calibration and test solutions
Measure each calibration and test solution three times using a constant injection volume according to the
requirements of the respective ion chromatograph. For each solution, the relative repeatability standard
deviation shall be lower than 0,5 %.
6.2.2.1.7 Expression of results
The sodium chlorate content of the test solution (y in mg/l) is calculated from the calibration line which
is obtained by linear regression with the five levels (four chlorate solutions and one blank solution) in
the calibration procedure.
The sodium chlorate (NaClO ) content of the laboratory sample, C , expressed in grams per kilograms is
3 2
given by Formula (3):
C yV× / m (3)
( )
2 22
where
y is the concentration of the test solution in milligrams per litre obtained via the regression
line of the calibration;
V is the volume, in millilitres, of the test solution (6.2.2.1.6.2);
m is the mass of the laboratory sample, in milligrams (6.2.2.1.6.2).
The sodium chlorate (NaClO ) content of the laboratory sample, C expressed in mass fraction in % of
3 3
available chlorine is given by Formula (4):
C × 10
( )
C = (4)
C
where
=
C is the sodium chlorate (NaClO ) content in g/kg of the laboratory sample;
2 3
C is the available chlorine (Cl ) content in mass fraction in % (6.2.1.6).
1 2
6.2.2.1.8 Repeatability limit
The absolute difference between two single test results, obtained under repeatability conditions, shall
not be greater than the repeatability value, r, as calculated from Formula (5):
r = 0,001 z (5)
where
z is the mean of the two results, expressed in mass fraction in %.
NOTE Repeatability conditions are conditions where mutually independent test results are obtained with the
same method on identical test material in the same laboratory by the same operator using the same equipment
within short intervals of time.
6.2.2.2 Determination of sodium bromate content (NaBrO )
6.2.2.2.1 General
This method is used to determine the bromate content, in the range between 2 mg/l and 1 000 mg/l, in
sodium hypochlorite solutions for commercial use. Results of inter-laboratory tests on sodium bromate
determination in sodium hypochlorite commercial solutions are specified in Annex E.
6.2.2.2.2 Principle
Direct determination of bromate ions in a diluted solution of sodium hypochlorite by ion chromatography
with suppressed conductimetric detection.
The range of measurement can be limited by analytical column capacity. A dilution of the sample in the
measurement range can be necessary. A convenient pre-treatment of the sample might be required
(for example to remove any chloride, sulfate, carbonate or metals).
Direct determination of bromate by separation and indirect UV detection may also be carried out. The
complete analytical procedure is specified in Annex D.
6.2.2.2.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall have a conductivity
of 0,056 μS/cm (conform to grade 1 as specified in EN ISO 3696:1995).
6.2.2.2.3.1 Sulfuric acid solution c(H SO ) = 0,025 mol/l regenerant solution.
2 4
6.2.2.2.3.2 Helium gas, high purity, for degassing eluant and regenerant solutions.
6.2.2.2.3.3 Stock sodium carbonate solution, c(Na CO ) = 0,5 mol/l
2 3
Dissolve 53,0 g of anhydrous sodium carbonate in 800 ml of water (grade 1, EN ISO 3696:1995) in
a 1 000 ml volumetric flask and make up to the volume with water (grade 1, EN ISO 3696:1995).
Store the solution at 2 °C to 6 °C in a polyethylene or glass bottle and renew it every 6 months.
6.2.2.2.3.4 Eluent carbonate solution, c(Na CO ) = 0,009 mol/l
2 3
Introduce 36 ml of the stock sodium carbonate solution 0,5 mol/l (6.2.2.2.3.3) into a 2 000 ml volumetric
flask and make up to the volume with water (grade 1, EN ISO 3696:1995).
Store the solution at 2 °C to 6 °C in polyethylene or glass bottle and renew it every week.
Degas the solution with helium (6.2.2.2.3.2) before use according to the instructions given by the
manufacturer.
Eluent should be maintained under an inert helium atmosphere to avoid carbonate contamination.
6.2.2.2.3.5 Stock standard bromate solution, ρ(BrO ) = 1 000 mg/l
Dry 1,5 g of potassium bromate for at least 1 h at 105 °C. Store the dried product in a desiccator. Weigh,
to the nearest 0,000 1 g, 1,305 7 g of the dry potassium bromate. Introduce into a 1 000 ml volumetric
flask. Dissolve in 800 ml of water (grade 1, EN ISO 3696:1995) and make up to the volume with water
(grade 1, EN ISO 3696:1995). Store the solution at 2 °C to 6 °C in polyethylene or glass bottle and renew
it every 12 months.
A commercial standard stock solution at required concentration may be also used.
6.2.2.2.3.6 Bromate standard solution, ρ(BrO ) = 10 mg/l
Introduce 1 ml of stock standard bromate solution (6.2.2.2.3.5) into a 100 ml volumetric flask. Make up
to the volume with water (grade 1, EN ISO 3696:1995).
Store the solution at 2 °C to 6 °C in polyethylene or glass bottle and renew it every 3 months.
6.2.2.2.4 Apparatus
Ordinary laboratory apparatus and glassware, together with the following.
6.2.2.2.4.1 Ion chromatograph
6.2.2.2.4.2 Chemical or electrochemical suppressed conductivity detector
6.2.2.2.4.3 Anionic column and pre-column
Resin composed of 15 μm polystyrene/divinylbenzene substrate agglomerated with anion exchange
latex that has been aminated.
6.2.2.2.4.4 Pre-treatment cartridges
— Cationic exchangers as Ag-form (Silver) (cartridge);
— cationic exchangers as H-form (Hydrogen) (cartridge).
If necessary, cationic exchangers as Ba-form (Barium) (cartridge) may be used to suppress sulfate
interferences.
6.2.2.2.4.5 Generator, of water (grade 1, EN ISO 3696:1995).
6.2.2.2.5 Chromatographic conditions
— Eluant flow rate: 1 ml/min;
— regenerant flow rate: 2,5 ml/min or electrochemical regeneration;
— recommended sampling loop size: 50 µl to 100 µl.
6.2.2.2.6 Procedure
6.2.2.2.6.1 Preparation of calibration solutions
Prepare calibration solutions in volumetric flasks by diluting accurately measured volumes of the
bromate stock solution (6.2.2.2.3.5) with the eluant carbonate solution (6.2.2.2.3.4) in accordance with
Table 3.
Table 3 — Calibration solutions for determination of bromate content
-
Solution BrO3 in mg/l NaBrO3 in mg/l
1 0,2 0,236
2 0,5 0,59
3 1 1,18
4 2 2,36
NOTE 1 Calibration is linear for concentration of bromate ion between 0,2 mg/l and 2 mg/l in the diluted
solution.
NOTE 2 The calibration solutions will be prepared freshly on the day of use.
6.2.2.2.6.2 Sample pre-treatment (if required)
If sample pre-treatment is necessary (presence of chloride and/or carbonate in large amount in the
sample that can interfere with the bromate determination), calibration solutions and diluted test
solutions shall be treated as follows:
— connect the cationic exchangers (cartridges) in series in order of Ag-H;
— using a 10 ml syringe, flush the cartridges with 10 ml of water;
— fill a 10 ml syringe with sample and attach it to the cartridge set;
— flush it with 5 ml of sample;
— continue to inject sample through the cartridges and collect the next 5 ml of treated sample for
analysis;
— purge the treated sample with helium gas for 5 min to remove the remaining carbonate.
If necessary, a Ba-form cartridge may be added to remove sulfate; the three pre-treatment cartridges
should then be attached in the following order: Ba-form, Ag-form, and H-form.
6.2.2.2.6.3 Preparation of test solutions
Weigh to the nearest 0,1 mg, 250 mg of the laboratory sample (record mass m in milligrams) into
a 100,0 ml measuring flask, fill up with eluant solution (6.2.2.2.3.4) and homogenize the test solution by
shaking the sealed flask carefully.
6.2.2.2.6.4 Measurement of calibration and test solutions
Measure each calibration solution and test solution three times using a constant injection volume
according to the requirements of the respective ion chromatograph. For each solution, the relative
repeatability standard deviation shall be lower than 0,5 %.
6.2.2.2.7 Expression of results
The sodium bromate content of the test (y in mg/l) is calculated from the calibration line which is
obtained by linear regression with the five levels (four bromate solutions and one blank solution) in the
calibration procedure. The sodium bromate (NaBrO ) content of the laboratory sample, C , expressed in
3 4
milligrams per kilogram is given by Formula (6):
C yV×× 10 / m (6)
( )
4 1 3 3
where
y is the concentration of the test solution in mg/l obtained via the regression line of the
calibration;
V is the volume in millilitres of the test solution (6.2.2.2.6.3);
m is the mass of the laboratory sample in milligrams (6.2.2.2.6.3).
The sodium bromate (NaBrO ) content of the laboratory sample, C , expressed in mass fraction of
3 5
available chlorine is given by Formula (7):
CC× 10 / C (7)
( )
54 1
where
C is the sodium bromate (NaBrO ) content in mg/kg of the laboratory sample;
4 3
C is the available chlorine (Cl ) content in mass fraction in % (6.2.1.6).
1 2
6.2.2.2.8 Repeatability limit
The absolute difference between two single test results, obtained under repeatability conditions, shall
not be greater than the repeatability value, r, as calculated from Formula (8):
r = 0,005 z (8)
where
z is the mean of the two results, expressed in mass fraction in %.
NOTE Repeatability conditions are conditions where mutually independent test results are obtained with the
same method on identical test material in the same laboratory by the same operator using the same equipment
within short intervals of time.
6.2.3 Chemical parameters
6.2.3.1 Determination of antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb),
nickel (Ni) and selenium (Se)
6.2.3.1.1 Principle
The elements arsenic, antimony, cadmium, chromium, lead, nickel and selenium are determined by
atomic absorption spectrometry.
6.2.3.1.2 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 2 as
specified in EN ISO 3696:1995.
6.2.3.1.2.1 Nitric acid, concentrated, density ρ = 1,42 g/ml.
=
=
6.2.3.1.3 Procedure
6.2.3.1.3.1 Test portion
Weigh, to the nearest 0,001 g, 20 g (m ) from the laboratory sample into a glass beaker.
6.2.3.1.3.2 Test solution
Evaporate until a wet residue is obtained, cool, add 1 ml of nitric acid (6.2.3.1.2.1), dilute with a few
millilitres of water, transfer quantitatively to a 100 ml volumetric flask, make up to the volume with water
and mix.
Carry out the evaporation carefully and not to dryness in order to avoid possible losses of arsenic and
selenium.
6.2.3.1.3.3 Determination
Determine the content of elements in the test solution (6.2.3.1.3.2) in accordance with the following
methods:
— Cd, Ni and Pb: In accordance with ISO 8288:1986, Method A;
— Cr: In accordance with EN 1233;
— As, Se and Sb: In accordance with the method given in Annex C.
These methods will give an interim result (y) expressed in milligrams per litre which needs to be
converted to give the final concentration according to the formula in 6.2.3.1.3.4.
6.2.3.1.3.4 Expression of results
From the interim result (y) determined (see 6.2.3.1.3.3), the content, C , of each element in the laboratory
sample, expressed in milligrams per kilogram of available chlorine is given by Formula (9):
V
Cy=×× (9)
mC
where
y is the interim result (6.2.3.1.3.3);
V is the volume, expressed in millilitres, of the test solution (6.2.3.1.3.2) (here V = 100 ml);
4 4
m is the mass, expressed in grams, of the test portion;
C is the available chlorine (Cl ) content in mass fraction in % (6.2.1.6).
1 2
6.2.3.2 Determination of mercury content (Hg)
6.2.3.2.1 Principle
The element mercury is determined by flameless atomic absorption spectrometry in accordance with
EN ISO 12846.
6.2.3.2.2 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 3 as
specified in EN ISO 3696:1995.
6.2.3.2.2.1 Nitric acid, mass fraction 65 %.
6.2.3.2.2.2 Sulfuric acid, mass fraction 30 %.
6.2.3.2.2.3 Hydroxylammonium chloride solution (NH OH·HCl) , mass fraction 10 %.
6.2.3.2.2.4 Tin(II) chloride solution, mass fraction 10 %.
6.2.3.2.3 Procedure
6.2.3.2.3.1 Test portion
Pipette 10 g (m ) of the laboratory sample and transfer to approximately 70 ml of water taking care to
avoid sputtering.
6.2.3.2.3.2 Test solution
Quantitatively transfer the test portion to a gas washing flask, capacity 250 ml, with the gas inlet equipped
with a porous glass frit. Dilute the contents of the gas washing flask with water to obtain a total volume
of 100 ml. Transfer to a volumetric flask (solution A).
Pipette accurately 5 ml of the sodium hypochlorite (solution A) and dilute in a 250 ml graduated gas
washing flask. During gentle shaking, add 30 ml of hydroxylammonium chloride solution (6.2.3.2.2.3),
5 ml of nitric acid (6.2.3.2.2.1) and 2 ml of tin(II) chloride solution (6.2.3.2.2.4) successively. Close
immediately the gas washing flask with the gas inlet equipped with a porous glass frit.
6.2.3.2.3.3 Determination
Proceed as specified in EN ISO 12846.
6.2.3.2.3.4 Expression of results
The interim result for mercury content (y) expressed in milligrams per litre is given by Formula (10):
V
T
yy× (10)
A
where
y is the result obtained, for the concentration of mercury in solution A, expressed in
A
milligrams per litre;
VT is the volume in millilitres of the test solution.
The content of mercury, C , in milligrams per kilogram of available chlorine is given by Formula (11):
10 100
C=y× × (11)
m C
5 1
where
m is the mass expressed in grams, of the test portion;
C is the available chlorine content in mass fraction in % (6.2.1.6).
7 Labelling - transportation - storage
7.1 Product labelling
The marking shall include the following:
=
— name “sodium hypochlorite solution”, trade name, grade and type;
— net mass;
— name and address of supplier and/or manufacturer;
— statement “this product conforms to EN 901”.
7.2 Labelling
The following labelling requirements shall apply to sodium hypochlorite at the date of publication of this
document.
Signal word:
Danger
Hazard statements:
H314: Causes severe skin burns and eye damage.
H400: Very toxic to aquatic life.
EUH031: Contact with acids liberates toxic gas
(chlorine)
Figure 1 — GHS 05
Figure 2 — GHS 09
Diluted solutions and substances shall be classified on the basis of their intrinsic properties.
NOTE The regulation [3] contains a list of substances already classified by the EU and the criteria by which
they are classified. It contains only a single entry for classification and labelling of the substance which is however
not appropriate for the various solutions placed on the market, since the hazards vary at different concentrations
depending on the individual content of free chlorine and free alkali; therefore, no classification for diluted solutions
can be given here.
7.3 Storage
7.3.1 General information
Sodium hypochlorite shall be protected against light, especially direct sunlight. It shall be stored at a cool
place in suitable con
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