EN 938:2016
(Main)Chemicals used for treatment of water intended for human consumption - Sodium chlorite
Chemicals used for treatment of water intended for human consumption - Sodium chlorite
This European Standard is applicable to sodium chlorite used for treatment of water intended for human consumption. It describes the characteristics of sodium chlorite and specifies the requirements and the corresponding test methods for sodium chlorite. It gives information on its use in water treatment.
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch - Natriumchlorit
Diese Europäische Norm gilt für Natriumchlorit zur Aufbereitung von Wasser für den menschlichen Gebrauch. Sie beschreibt die Eigenschaften von Natriumchlorit und legt die Anforderungen sowie die entsprechenden Prüfverfahren für Natriumchlorit fest. Sie enthält Angaben zu dessen Anwendung in der Wasseraufbereitung.
Produits chimiques utilisés pour le traitement de l'eau destinée à la consommation humaine - Chlorite de sodium
La présente Norme européenne s’applique au chlorite de sodium utilisé pour le traitement de l’eau destinée à la consommation humaine. Elle décrit les caractéristiques du chlorite de sodium et spécifie les exigences et les méthodes d’essai correspondantes. Elle donne des informations sur son emploi pour le traitement de l’eau.
Kemikalije, ki se uporabljajo za pripravo pitne vode - Natrijev klorit
Ta evropski standard se uporablja za natrijev klorit, ki se uporablja za pripravo pitne vode. Opisuje lastnosti natrijevega klorita ter določa zahteve in ustrezne preskusne metode zanj. Podaja informacije za njegovo uporabo pri pripravi vode.
General Information
Relations
Standards Content (Sample)
SLOVENSKI STANDARD
01-julij-2016
1DGRPHãþD
SIST EN 938:2009
Kemikalije, ki se uporabljajo za pripravo pitne vode - Natrijev klorit
Chemicals used for treatment of water intended for human consumption - Sodium
chlorite
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch - Natriumchlorit
Produits chimiques utilisés pour le traitement de l'eau destinée à la consommation
humaine - Chlorite de sodium
Ta slovenski standard je istoveten z: EN 938:2016
ICS:
13.060.20 Pitna voda Drinking water
71.100.80 .HPLNDOLMH]DþLãþHQMHYRGH Chemicals for purification of
water
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.
EN 938
EUROPEAN STANDARD
NORME EUROPÉENNE
May 2016
EUROPÄISCHE NORM
ICS 71.100.80 Supersedes EN 938:2009
English Version
Chemicals used for treatment of water intended for human
consumption - Sodium chlorite
Produits chimiques utilisés pour le traitement de l'eau Produkte zur Aufbereitung von Wasser für den
destinée à la consommation humaine - Chlorite de menschlichen Gebrauch - Natriumchlorit
sodium
This European Standard was approved by CEN on 18 March 2016.
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, 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: Avenue Marnix 17, B-1000 Brussels
© 2016 CEN All rights of exploitation in any form and by any means reserved Ref. No. EN 938:2016 E
worldwide for CEN national Members.
Contents Page
European foreword . 4
Introduction . 5
1 Scope . 6
2 Normative references . 6
3 Description . 6
3.1 Identification . 6
3.1.1 Chemical name . 6
3.1.2 Synonym or common name . 6
3.1.3 Relative molecular mass . 6
3.1.4 Empirical formula . 6
3.1.5 Chemical formula . 6
3.1.6 CAS Registry Number . 6
3.1.7 EINECS reference . 7
3.2 Commercial form . 7
3.3 Physical properties . 7
3.3.1 Appearance . 7
3.3.2 Density . 7
3.3.3 Solubility in water . 7
3.3.4 Vapour pressure . 7
3.3.5 Boiling point at 100 kPa . 7
3.3.6 Crystallization point . 7
3.3.7 Specific heat . 8
3.3.8 Viscosity (dynamic) . 8
3.3.9 Critical temperature . 8
3.3.10 Critical pressure . 8
3.3.11 Physical hardness . 8
3.4 Chemical properties . 8
4 Purity criteria . 8
4.1 General . 8
4.2 Composition of commercial product . 9
4.3 Impurities and main by-products . 9
4.4 Chemical parameters . 9
5 Test methods . 10
5.1 Sampling . 10
5.1.1 General . 10
5.1.2 Sampling from drums and bottles . 10
5.1.3 Sampling from tanks and tankers . 10
5.2 Analysis . 11
5.2.1 Determination of sodium chlorite (main product) . 11
5.2.2 Impurities . 12
5.2.3 Chemical parameters . 15
6 Labelling - Transportation - Storage . 17
6.1 Means of delivery . 17
6.2 Labelling according to the EU Legislation . 17
6.3 Transportation regulations and labelling . 17
6.4 Marking . 18
6.5 Storage . 18
6.5.1 General . 18
6.5.2 Long term stability . 18
6.5.3 Storage incompatibilities . 18
Annex A (informative) General information on sodium chlorite . 19
A.1 Origin . 19
A.1.1 Raw materials . 19
A.1.2 Manufacturing process . 19
A.2 Use . 19
A.2.1 Function . 19
A.2.2 Form in which it is used. 19
A.2.3 Treatment dose . 19
A.2.4 Means of application . 19
A.2.5 Secondary effects . 19
A.2.6 Removal of excess product . 20
A.3 Routine analyses . 20
A.3.1 Determination of sodium chlorite (NaClO2) . 20
-
A.3.2 Determination of chlorate ion (ClO ). 22
A.3.3 Determination of chemical parameters . 23
Annex B (normative) General rules relating to safety . 24
B.1 Rules for safe handling and use . 24
B.2 Emergency procedures . 24
B.2.1 First aid . 24
B.2.2 Spillage . 24
B.2.3 Fire . 24
Annex C (normative) Determination of arsenic, antimony and selenium (atomic absorption
spectrometry hydride technique) . 25
C.1 Safety precautions . 25
C.2 General principle . 25
C.3 Interferences . 25
C.4 Reagents . 25
C.5 Apparatus . 27
C.6 Procedure . 29
C.6.1 Preparation of the apparatus . 29
C.6.2 Preparation of calibration solutions . 30
C.6.3 Preparation of test solutions and standard solutions . 30
C.6.4 Determination of arsenic with sodium borohydride . 30
C.6.5 Determination of selenium with sodium borohydride . 30
C.6.6 Determination of antimony with sodium borohydride . 31
C.7 Calculation. 31
Bibliography . 32
European foreword
This document (EN 938:2016) 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 November 2016, and conflicting national standards
shall be withdrawn at the latest by November 2016.
Attention is drawn to the possibility that some of the elements of this document may be the subject of
patent rights. CEN [and/or CENELEC] shall not be held responsible for identifying any or all such patent
rights.
This document supersedes EN 938:2009.
Significant technical differences between this edition and EN 938:2009 are as follows:
a) deletion of reference to EU Directive 67/548/EEC of June 27, 1967 in order to take into account the
latest Regulation in force (see [2]);
b) use of the changed classification and labelling (see [2]).
According to the CEN/CENELEC Internal Regulations, the national standards organizations 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, Slovakia, Slovenia, Spain, Sweden, Switzerland,
Turkey 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 European Standard:
a) this European Standard 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 the 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 European Standard is subject to
regulation or control by National Authorities.
1 Scope
This European Standard is applicable to sodium chlorite used for treatment of water intended for
human consumption. It describes the characteristics of sodium chlorite and specifies the requirements
and the corresponding test methods for sodium chlorite. It gives information on its use in water
treatment.
2 Normative references
The following documents, in whole or in part, are normatively referenced in this document and are
indispensable for its application. 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)
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, Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame
atomic absorption spectrometric methods
ISO 9174, Water quality — Determination of chromium — Atomic absorption spectrometric methods
3 Description
3.1 Identification
3.1.1 Chemical name
Sodium chlorite.
3.1.2 Synonym or common name
None.
3.1.3 Relative molecular mass
90,44.
3.1.4 Empirical formula
NaClO .
3.1.5 Chemical formula
Na-O-Cl = O.
1)
3.1.6 CAS Registry Number
7758-19-2.
1) Chemical Abstracts Service Registry Number.
2)
3.1.7 EINECS reference
231-836-6.
3.2 Commercial form
The product is supplied as a powder or as an aqueous solution of sodium chlorite.
3.3 Physical properties
3.3.1 Appearance
The products are either a white powder or a greenish-yellow aqueous solution.
3.3.2 Density
The density of sodium chlorite solutions is given in Table 1.
Table 1 — Density of sodium chlorite solutions
Aqueous solution concentration Density
% (mass fraction) g/ml at 20 °C
25 1,210
31 1,270
3.3.3 Solubility in water
The solubility of sodium chlorite depending on temperature is given in Table 2.
Table 2 — Solubility of sodium chlorite
Temperature Solubility
°C g/l
5 340
17 390
30 460
45 530
60 550
3.3.4 Vapour pressure
Not applicable.
3)
3.3.5 Boiling point at 100 kPa
Not applicable.
3.3.6 Crystallization point
The crystallization point of sodium chlorite depending on concentration is given in Table 3.
2) European Inventory of Existing Commercial Chemical Substances.
3) 100 kPa = 1 bar.
Table 3 — Crystallization point of sodium chlorite
Aqueous solution concentration Crystallization point
% (mass fraction) °C
25 − 14,5
31 3
3.3.7 Specific heat
Not known.
3.3.8 Viscosity (dynamic)
The viscosity of sodium chlorite depending on concentration is given in Table 4.
Table 4 — Viscosity of sodium chlorite
Aqueous solution concentration Viscosity
% (mass fraction) mPa.s at 20 °C
25 2,33
31 3,26
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
Sodium chlorite is a strong oxidizing agent. It generates chlorine dioxide with acidic solutions or
chlorine and reacts with organic compounds.
4 Purity criteria
4.1 General
This European Standard specifies the minimum purity requirements for sodium chlorite 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 the relevant authorities.
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 the product standard.
Limits have been given for impurities and chemicals 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 leads 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 sodium chlorite is available as a powder or as an aqueous solution with sodium chlorite content
of 7,5 percent by mass fraction to 35 percent by mass fraction.
The content of sodium chlorite shall be equal to or greater than the manufacturer’s declared value.
4.3 Impurities and main by-products
The product shall conform to the requirements specified in Table 5.
Table 5 — Impurities
Impurity Limit
g/kg sodium chlorite
100 % mass fraction
Sodium chlorate (NaClO ) max. 40
Sodium nitrate (NaNO ) max. 1
NOTE Sodium chlorate can be a by-product of the manufacturing process.
4.4 Chemical parameters
NOTE For the purposes of this standard, “chemical parameters” are those defined in the
EU Directive 98/83/EC of November 13, 1998 (see [1]).
The content of chemical parameters shall conform to the requirements specified in Table 6.
Table 6 — Chemical parameters
Parameter Limit
mg/kg sodium chlorite
100 % mass fraction
Type 1 Type 2
Arsenic (As) max. 1,1 7,5
Cadmium (Cd) max. 1,5 7,5
Chromium (Cr) max. 1,1 7,5
Mercury (Hg) max. 1,1 3,7
Nickel (Ni) max. 1,1 7,5
Lead (Pb) max. 1,1 7,5
Antimony (Sb) max. 1,1 7,5
Selenium (Se) max. 1,1 7,5
NOTE Cyanide which does not exist in a strong oxidizing medium such as
sodium chlorite is not a relevant chemical parameter. Pesticides and polycyclic
aromatic hydrocarbons are not by-products of the manufacturing process.
5 Test methods
5.1 Sampling
5.1.1 General
Observe the general recommendations of ISO 3165 and take ISO 6206 into account.
5.1.2 Sampling from drums and bottles
5.1.2.1 General
5.1.2.1.1 Mix the contents of the 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 to 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 a
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.
5.2 Analysis
5.2.1 Determination of sodium chlorite (main product)
5.2.1.1 General
This method applies to the measurements of sodium chlorite content in commercial sodium chlorite
solutions and is specific for these species.
5.2.1.2 Principle
Automated iodometric titration with an excess of sulfuric acid. This method is based on the reducing
action of the iodide ion on the chlorite species and on the subsequent determination of iodine formed,
by redox titration against sodium thiosulfate; the potential step is located around 230 mV.
5.2.1.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 in
accordance with EN ISO 3696.
5.2.1.3.1 Sulfuric acid solution, c(H SO ) = 0,5 mol/l.
2 4
5.2.1.3.2 Sodium thiosulfate standard volumetric solution, c(Na S O .5H O) = 0,1 mol/l.
2 2 3 2
Dissolve 24,8 g of Na S O .5H O in water. Add 0,5 ml of chloroform as preservative, dilute to volume
2 2 3 2
with water in a 1 000 ml one-mark volumetric flask and mix thoroughly.
To standardize: Weigh, to the nearest 0,1 mg, (160 ± 10) mg (m) of primary standard potassium
dichromate into a tared glass beaker. Place the contents of the beaker in a 500 ml stoppered conical
flask, add 100 ml of water and (2 ± 0,5) g of potassium iodide and stir to dissolve. Add (15 ± 1) ml of
hydrochloric acid solution (diluted 1 + 1 by volume), swirl, and allow to stand for 5 min. Titrate with the
sodium thiosulfate solution until the solution is pale yellow. Add (5 ± 1) ml of starch solution 1 % (mass
fraction) and titrate to the end point, i.e. to the disappearance of the blue-black colour. Record the
volume (V) used.
The concentration, c, of the sodium thiosulfate standard volumetric solution (Na S O .5H O), expressed
2 2 3 2
in moles per litre is given by the following formula:
m
c = (1)
V,× 49 0317
where
is the mass, in milligrams, of potassium dichromate (K Cr O ) weighed;
m 2 2 7
V is the volume, in millilitres, of the sodium thiosulfate standard volumetric solution used.
5.2.1.3.3 Potassium iodide.
5.2.1.4 Apparatus
Ordinary laboratory apparatus and glassware with together the following:
5.2.1.4.1 Automatic potentiometric titrimeter.
5.2.1.4.2 Automatic burette, 10 ml, equipped with an injection tip.
5.2.1.4.3 Electromechanical stirrer.
5.2.1.4.4 Glass titration beaker, 400 ml.
5.2.1.4.5 Platinum – Silver/Silver-chloride combination electrode with a porous plug
electrolytic junction.
5.2.1.5 Procedure
5.2.1.5.1 Test solution
Weigh, to the nearest 0,1 mg, a test portion (m) between 0,11 g and 0,15 g the laboratory sample.
5.2.1.5.2 Determination
Transfer the test solution (5.2.1.5.1) to a 400 ml titration beaker with 300 ml of water and 4 g of
potassium iodide (5.2.1.3.3) and add, with stirring, 20 ml of H SO (5.2.1.3.1).
2 4
Input the calculation data in the titration microprocessor in accordance with the instruction manual.
Introduce the electrode into the titration beaker and titrate with the sodium thiosulfate standard
volumetric solution (5.2.1.3.2).
5.2.1.6 Expression of results
The sodium chlorite (NaClO ) content, C , expressed as a percentage by mass (% of mass fraction) is
2 1
given by the following formula; assume 90,44 g of sodium chlorite (NaClO ) is equivalent to 1 000 ml of
sodium thiosulfate c(Na S O .5H O) = 0,1 mol/l:
2 2 3 2
Vc× × 2,262
(2)
C =
m
where
V is the volume, in millilitres, of the sodium thiosulfate standard volumetric solution (5.2.1.3.2)
used for the titration at the end point;
c is the concentration, moles per litre, of the sodium thiosulfate standard volumetric solution
(5.2.1.3.2);
m is the mass in grams of the test portion (5.2.1.5.1).
5.2.2 Impurities
5.2.2.1 Determination of sodium chlorate content (NaClO3)
5.2.2.1.1 General
This method is used to determine the chlorate content, in the range between 3,75 g/l and 15 g/l, in
sodium chlorite solutions for commercial use; it is specific for these species.
5.2.2.1.2 Principle
Direct determination of chlorate ion in a diluted solution of sodium chlorite by separation and chemical
suppressed conductimetric detection (ionic chromatography).
NOTE Calibration is linear for concentration of chlorate ion between 3,75 mg/l and 15 mg/l in the diluted
solution.
5.2.2.1.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 in
accordance with EN ISO 3696.
5.2.2.1.3.1 Sodium carbonate and sodium hydrogen carbonate, eluant solution.
Mix one volume of sodium carbonate c(Na CO ) = 2 mol/l with one volume of sodium hydrogen
2 3
carbonate c(NaHCO ) = 0,75 mol/l.
5.2.2.1.3.2 Sulfuric acid solution c(H SO ) = 0,025 mol/l regenerant solution.
2 4
5.2.2.1.3.3 Helium gas, high purity, for degassing eluant and regenerant solutions.
5.2.2.1.3.4 Water, ultra pure, conductivity = 0,056 μS/cm.
5.2.2.1.3.5 Sodium chlorate stock solution at 1 g/l:
Weigh, to the nearest 0,000 1 g, 0,255 1 g of NaClO . Dissolve in 200 ml of the ultrapure water
(5.2.2.1.3.4).
5.2.2.1.4 Apparatus
Ordinary laboratory apparatus and glassware, together with the following:
5.2.2.1.4.1 Ion chromatograph.
5.2.2.1.4.2 Chemical suppressed conductivity detector.
5.2.2.1.4.3 Anionic column and precolumn:
Resin composed of 15 μm polystyrene/divinylbenzene substrate agglomerated with anion exchange
latex that has been aminated.
5.2.2.1.4.4 Data logger/plotter able to record and display the chromatographic peak heights.
5.2.2.1.4.5 Densimeter, temperature setting 20 °C.
5.2.2.1.5 Chromatographic conditions
a) Eluant flow rate: 2 ml/min;
b) regenerant flow rate: 2,5 ml/min;
c) full scale of conductivity: 30 mS;
d) residual conductivity: < 18 mS;
-
e) linearity range: ClO : 1 mg/l to 15 mg/l of injected solution.
Calibration conditions:
Four levels of calibration and a blank level. Each level is measured three times.
5.2.2.1.6 Procedure
5.2.2.1.6.1 Preparation of calibration solutions
Prepare chlorate standard solutions by diluting the sodium chlorate stock solution (5.2.2.1.3.5) with the
eluant solution (5.2.2.1.3.1), prepare calibration solutions in accordance with Table 7.
Table 7 — Calibration solution for determination of chlorate content
-
Solution ClO3 in mg/l
1 3,75
2 7,5
3 11,25
4 15
5.2.2.1.6.2 Preparation of test solution
Heat the sodium chlorite laboratory sample to 20 °C and check the density in grams per millilitre with a
densimeter (5.2.2.1.4.5) set for 20 °C.
Prepare dilutions with the eluant solution (5.2.2.1.3.1) in order to be within the range of calibration.
5.2.2.1.6.3 Measurement of calibration and test solutions
Measure each calibration solution three times; for each solution the relative standard deviation shall be
lower than 0,5 %.
Dilute each test solution in order to obtain two levels of concentration located respectively in the lower
part of the calibration curve and in the upper part of the calibration curve. Repeat the measurements
twice more in order to keep the relative standard deviation at not more than 0,5 %.
5.2.2.1.7 Expression of results
The chlorate content, of the test solution is obtained from the regression line obtained with the five
levels of calibration results in the sodium chlorite solution.
-
The chlorate (ClO ) content of the laboratory sample, C , expressed in milligrams per litre is given by
3 2
the following general formula:
V
C y× (3)
m
where
y is the concentration obtained from calibration curve;
V is the volume, in millilitres, of the dilution;
m is the mass, in grams, of the test solution.
The sodium chlorate (NaClO ) content, C , expressed in grams per kilogram of sodium chlorite of a mass
3 3
fraction of 100 % is given by the following formula:
C
C C× (4)
100×ρ
where
C is the sodium chlorite content in percentage by mass (5.2.1.6);
=
=
p is the density, in grams per millilitre of the sodium chlorite solution.
5.2.2.1.8 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 the following formula:
r = 0,05 z (5)
where
z is the mean of the two results, expressed in grams per kilogram.
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.
5.2.3 Chemical parameters
5.2.3.1 Determination of antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb),
nickel (Ni) and selenium (Se)
5.2.3.1.1 Principle
The elements arsenic, antimony, cadmium, chromium, lead, nickel and selenium are determined by
atomic absorption spectrometry.
5.2.3.1.2 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to the
appropriate grade specified in EN ISO 3696.
5.2.3.1.2.1 Nitric acid, concentrated, density ρ = 1,42 g/ml.
5.2.3.1.3 Procedure
5.2.3.1.3.1 Test portion
Weigh, to the nearest 0,001 g, 20 g (m ) from the laboratory sample into a glass beaker.
5.2.3.1.3.2 Test solution
Evaporate until a wet residue is obtained, cool, add 1 ml of nitric acid (5.2.3.1.2.1), dilute with a few
millilitres of water, transfer quantitatively to a 100 ml volumetric flask and dilute to volume with water
and mix.
Carry out the evaporation carefully and not to dryness in order to avoid possible losses of arsenic and
selenium.
5.2.3.1.3.3 Determination
Determine the content of toxic substances in the test solution (5.2.3.1.3.2) in accordance with the
following methods:
— Cd, Ni and Pb: in accordance with ISO 8288, Method A;
— Cr: in accordance with ISO 9174;
— 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
corrected to give the final concentration according to the formula in 5.2.3.1.4.
5.2.3.1.4 Expression of results
From the interim results (y) determined (see 5.2.3.1.3.3), the content, C4, of each chemical parameter in
the laboratory sample, expressed in milligrams per kilogram of sodium chlorite of a mass fraction
of 100 % is calculated from the following general formula:
V
(6)
C=y××
m C
3 1
where
y is the interim result (5.2.3.1.3.3);
V is the volume, in millilitres, of the test solution (5.2.3.1.3.2) (= 100 ml);
m is the mass, expressed in grams, of the test portion;
C is the sodium chlorite (NaClO ) content in percentage by mass (5.2.1.6).
1 2
5.2.3.2 Determination of mercury (Hg)
5.2.3.2.1 Principle
The element mercury is determined by flameless atomic absorption spectrometry in accordance with
EN ISO 12846.
5.2.3.2.2 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to the
appropriate grade specified in EN ISO 3696.
5.2.3.2.2.1 Potassium permanganate solution, ρ(KMnO ) = 50 g/l.
5.2.3.2.2.2 Sulfuric acid, concentrated, density P = 1,84 g/ml.
5.2.3.2.2.3 Hydroxylammonium chloride, c(NH2OH.HCl) = 100 g/l.
5.2.3.2.2.4 Potassium dichromate solution, ρ(K Cr O ) = 4 g/l in a volume fraction of 50 % of
2 2 7
nitric acid solution.
5.2.3.2.3 Procedure
5.2.3.2.3.1 Test portion
Pipette 10 g (m ) of the laboratory sample and transfer to approximately 70 ml of water taking care to
avoid sputtering.
5.2.3.2.3.2 Test solution
Quantitatively transfer the test portion to a washing flask (e.g. Durand bottle), capacity 250 ml, the gas
inlet of which is made of a porous frit. Dilute the contents of the washing flask with water to obtain a
total volume of 100 ml. Transfer to a volumetric flask (solution A).
Pipette, accurately 10 ml of the solution A. Transfer to a 250 ml conical flask add 60 ml of water, 20 ml
of a potassium permanganate solution (5.2.3.2.2.1) and five 1 ml portions of sulfuric acid (5.2.3.2.2.2).
Heat and keep boiling for 10 min. Allow to cool. Just dissolve the precipitate (MnO) with
hydroxylammonium chloride (5.2.3.2.2.3), add 5 ml of the potassium dichromate solution (5.2.3.2.2.4)
and transfer to a 100 ml (V ) volumetric flask. Dilute to the mark with water and mix.
T
5.2.3.2.3.3 Determination
Proceed as described in EN ISO 12846.
5.2.3.2.4 Expression of results
The interim result for mercury content (y) expressed in milligrams per litre is given by the following
general formula:
V
T
yy× (7)
A
where
y is the result obtained, for the concentration of mercury in solution A, expressed in milligrams
A
per litre;
V is the volume in millilitres of the test solution.
T
The content of mercury, C , in milligrams per kilogram of sodium chlorite, mass fraction of 100 % is
given by the following formula:
10 100
(8)
Cy5=××
mC
4 1
where
m is the mass, expressed in grams, of the test portion;
C is the sodium chlorite content in percentage by mass (5.2.1.6).
6 Labelling - Transportation - Storage
6.1 Means of delivery
Sodium chlorite shall be delivered in polyethylene drums containers or tankers of up to 25 t capacity.
In order that the purity of the products 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 Labelling according to the EU Legislation
At the date of publication of this document, Sodium chlorite is not listed within Annex VI of
Regulation (EC) No 1272/2008 [2]
Annex VI of Regulation (EC) No 1272/2008 [2] and its amendments and adaptations to technical
progress contain a list of substances classified by the EU. Substances which are not in this Annex VI
should be classified on the basis of their intrinsic properties according to the criteria in the Regulation
by the person responsible for the marketing of the substance.
6.3 Transportation regulations and labelling
5)
Sodium chlorite solid is listed as UN Number 1496.
4) See [2].
=
6) 7)
RID ADR : Class 5.1, code O , packing group II.
8)
IMDG : Class 5.1, Packing group II.
9)
IATA : Class 5.1, Packing group II.
5)
Sodium chlorite solution is listed as UN Number 1908.
6) 7)
RID ADR : Class 8, code C9, packing group II.
8)
IMDG : Class 8, Packing group II.
9)
IATA : Class 8, Packing group II.
6.4 Marking
The marking shall include the following:
a) name “Sodium chlorite”, trade name and grade;
b) net mass ;
c) name and address of supplier and/or manufacturer;
d) statement “this product conforms to EN 938, type,…”.
6.5 Storage
6.5.1 General
The product shall be stored in containers used exclusively for sodium chlorite. It shall be stored away
from direct sunlight, in a cool, well-ventilated area, but at a temperature not lower than the
crystallization point (see 3.3.6). Large quantities shall be stored outdoors or in a room equipped with an
automatic fire-extinguishing system. Refer to local authorities regulations.
6.5.2 Long term stability
The product is stable for at least one year.
6.5.3 Storage incompatibilities
The product shall not be allowed to come into contact with acids, acidic salts, reducing agents or organic
compounds (wood, paper, grease,…).
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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