SIST EN 12671:2016

SLOVENSKI STANDARD
oSIST prEN 12671:2014
01-september-2014
Kemikalije, ki se uporabljajo za pripravo pitne vode - Klorov dioksid, proizveden na
kraju samem
Chemicals used for treatment of water intended for human consumption - Chlorine
dioxide generated in situ
Produkte zur Aufbereitung von Wasser für den menschlichen Gebrauch - Vor Ort
erzeugtes Chlordioxid
Produits chimiques utilisés pour le traitement de l’eau destinée à la consommation
humaine - Dioxyde de chlore généré in situ
Ta slovenski standard je istoveten z: prEN 12671
ICS:
13.060.20 Pitna voda Drinking water
71.100.80 .HPLNDOLMH]DþLãþHQMHYRGH Chemicals for purification of
water
oSIST prEN 12671:2014 en,fr,de
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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oSIST prEN 12671:2014

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oSIST prEN 12671:2014

EUROPEAN STANDARD
DRAFT
prEN 12671
NORME EUROPÉENNE

EUROPÄISCHE NORM

June 2014
ICS 71.100.80 Will supersede EN 12671:2009
English Version
Chemicals used for treatment of water intended for human
consumption - Chlorine dioxide generated in situ
Produits chimiques utilisés pour le traitement de l'eau Produkte zur Aufbereitung von Wasser für den
destinée à la consommation humaine - Dioxyde de chlore menschlichen Gebrauch - Vor Ort erzeugtes Chlordioxid
généré in situ
This draft European Standard is submitted to CEN members for enquiry. It has been drawn up by the Technical Committee CEN/TC 164.

If this draft becomes a European Standard, 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.

This draft European Standard was established by CEN 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.

Recipients of this draft are invited to submit, with their comments, notification of any relevant patent rights of which they are aware and to
provide supporting documentation.

Warning : This document is not a European Standard. It is distributed for review and comments. It is subject to change without notice and
shall not be referred to as a European Standard.


EUROPEAN COMMITTEE FOR STANDARDIZATION
COMITÉ EUROPÉEN DE NORMALISATION

EUROPÄISCHES KOMITEE FÜR NORMUNG

CEN-CENELEC Management Centre: Avenue Marnix 17, B-1000 Brussels
© 2014 CEN All rights of exploitation in any form and by any means reserved Ref. No. prEN 12671:2014 E
worldwide for CEN national Members.

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Contents
Page
Foreword .3
Introduction .4
1 Scope .5
2 Normative references .5
3 Description .5
3.1 Identification .5
3.2 Presentation form .6
3.3 Physical properties .6
3.4 Chemical properties .8
4 Purity criteria .8
4.1 General .8
4.2 Composition of in-situ generated product .8
4.3 Impurities and main by-products .8
4.4 Chemical parameters .9
5 Test methods .9
5.1 Sampling .9
5.2 Determination of chlorine dioxide and chlorite concentrations .9
6 Labelling - Storage - Distribution system . 13
6.1 Labelling according to the EU legislation . 13
6.2 Means of distribution . 15
6.3 Storage, stability . 15
Annex A (informative) General information on chlorine dioxide . 16
A.1 Origin . 16
A.2 Use . 17
A.3 Spectrometric method for specific determination of CIO . 17
2
A.4 Determination of chlorite and chlorate ions contents in aqueous chlorine dioxide as
produced by the reactors . 20
Annex B (normative) General rules relating to safety . 23
B.1 Rules for safe handling and use . 23
B.2 Emergency procedures . 23
Bibliography . 24


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Foreword
This document (prEN 12671:2014) has been prepared by Technical Committee CEN/TC 164 “Water supply”,
the secretariat of which is held by AFNOR.
This document is currently submitted to the CEN Enquiry.
This document will supersede EN 12671:2009.
Significant technical differences between this edition and EN 12671:2009 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 [3]);
b) section 6.2 – updating of risk and safety labelling according to EU Regulation [3] and its latest
Adaptations to Technical Progress):
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Introduction
In respect of potential adverse effects on the quality of water intended for human consumption, caused by the
product covered by this document:
1) 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;
2) 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 1 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.
NOTE 2 This product is a biocide and has to comply with the relevant legislation in force. In the European Union, at the
time of publication, this legislation is REGULATION (EU) No 528/2012 [2]).
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1 Scope
This document is applicable to chlorine dioxide generated on site for treatment of water intended for human
consumption. It describes the characteristics for chlorine dioxide and specifies the composition and the
corresponding test methods for chlorine dioxide. It gives information on its use in water treatment. It also
determines the rules relating to safe handling and use of chlorine dioxide generated on site (see Annex B).
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)
ISO 3165, Sampling of chemical products for industrial use — Safety in sampling
ISO 6206, Chemical products for industrial use — Sampling —Vocabulary
3 Description
3.1 Identification
3.1.1 Chemical name
Chlorine dioxide.
3.1.2 Synonym or common name
None.
3.1.3 Relative molecular mass
67,46
3.1.4 Empirical formula
ClO

2
3.1.5 Chemical formula
_ _
O Cl O (resonance structure)
 
1)
3.1.6 CAS Registry Number
10049-04-4
2)
3.1.7 EINECS reference
233-162-8

1) Chemical Abstracts Service Registry Number.
2) European Inventory of Existing Commercial Chemical Substances.
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3.2 Presentation form
For water treatment, chlorine dioxide is generated in situ as an aqueous solution on or near the site of use and
transferred to the site of use.
3.3 Physical properties
3.3.1 Appearance
The pure product is an orange gas or liquid, which forms a yellow solution in water.
Note 1 to entry: If the solution becomes red-brown, it is sign of decomposition.
3.3.2 Density
3)
Gas: 3,09 g/l, (2,4 g/l relative, air = 1) at 273 K and 101,3 kPa .
Liquid: 1,64 g/ml at 20 °C.
3.3.3 Solubility in water
In Table 1 the solubility values (S) for chlorine dioxide are given in grams per m³ water at a pressure of
101,3 kPa for different temperatures 1:
Table 1 — Solubility values
Temperature of water 3
g/m H O
2
S value :
°C
3
g/m gas
0
70 ± 0,7
5 (60,3)
10 (53,7)
15 45
20 (42,7)
25 (33)
30 (30,1)
35
26,5 ± 0,8
NOTE 1 S is a ratio, not an absolute value of concentration.
NOTE 2 The S values are directly measured values except those in brackets which are extrapolated data.

3 ) 100 kPa = 1 bar
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3.3.4 Vapour pressure
The vapour pressure of pure chlorine dioxide as a function of temperature is given in Table 2.

Table 2 — Vapour pressure of pure chlorine dioxide
Temperature Vapour pressure
[C°] [kPa]
0 82,3
5 90,4
10 98,8
11 100,5
20 116,5 (extrapolated)
25 125,8 (extrapolated)
30 135,3 (extrapolated)
35 145,1 (extrapolated)
40 155,0 (extrapolated)
4)
3.3.5 Boiling point at 101,3 kPa
11 °C (for pure chlorine dioxide).
3.3.6 Crystallisation point
- 59 °C (for pure chlorine dioxide).
3.3.7 Specific heat
The specific heat of solutions of chlorine dioxide is very similar to that of pure water.
3.3.8 Viscosity (dynamic)
The dynamic viscosity of solutions of chlorine dioxide is very similar to that of pure water.
3.3.9 Critical temperature
153 °C (for pure chlorine dioxide).
3.3.10 Critical pressure
Not applicable.
3.3.11 Physical hardness
Not applicable.
3.3.12 Dissolution heat
The heat of the dissolution in water is – 26,8 kJ/mol (exothermic).

4) 100 kPa = 1 bar
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3.4 Chemical properties
Chlorine dioxide is a molecule containing an unpaired electron and has the characteristics of a
"molecule-free-radical". Relevant Redox potentials of chlorine dioxide and related molecules are (E values at
o

25 °C in volts):
+ - -
+ 3H + 4e ⇒ CI + 2H O 1,57
HCIO
2 2
- -
CIO (dissolved gas) + 1e ⇒ CIO 1,15
2 2
- - +
CIO + 1e + 2H ⇒ ClO + H O 1,15
3 2 2
- -
ClO (dissolved liquid) + 1e ⇒ CIO 0,95
2
2
- - + -
CIO + 4e + 4 H ⇒ CI + 2H O 0,78
2 2
4 Purity criteria
4.1 General
This European Standard specifies the minimum purity requirements for chlorine dioxide generated in situ 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 in-situ generated product
Chlorine dioxide (ClO ) is produced as aqueous solution on or near the site of use. For safety reasons the
2
aqueous ClO -solution without intermediate storage in a storage tank (i.e. without headspace) may not exceed
2
a concentration of 20 g/l.
The concentration of the aqueous ClO solution with intermediate storage in a storage tank (i.e. with
2
headspace) should not exceed a concentration of 3 g/l, to ensure an adequate distance to the explosion limit
(see B.1).
4.3 Impurities and main by-products
Impurities and main by-products of the starting products used for the generation (indicated in A.1.1) can be
found in the in situ generated product in respective proportional concentrations.
Inadequate design, operation and maintenance of reactors can give rise to the formation of chlorine and
traces of chlorate ion and, eventually, the presence of unreacted chlorite, chlorate and/or chlorine (see [6]); for
analysis see 5.2 and A.4.
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4.4 Chemical parameters
Limits of chemical parameters being potentially present in chlorine dioxide solution have been specified in the
corresponding EN standards of the starting products (indicated in A.1.1).
5 Test methods
5.1 Sampling
Sampling of chlorine dioxide solutions shall avoid photochemical decompositions, losses by evaporation of the
product and consumption by the glassware and dilution water. Samples shall be taken at the exit of the
reactor or from the storage tank with a sampling tube and the analytical procedures started as fast as
possible.
In order to achieve these objectives the following step by step procedure shall be adopted:
 sampling shall be made in accordance with the general requirements given in ISO 3165 and take into
account ISO 6206;
 all glassware is to be conditioned immediately before sampling, with the solution under investigation and
this preliminary rinsing sample is to be discarded;
 liquid samples for analytical control shall be introduced directly into the analytical reagent solutions; the
sampling device and procedure shall take care that the sample is directly contacted with the analytical
reagent without running along the walls of the analytical glassware;
 the sample vessels shall be stoppered leaving no -or only a little- a head-space, to store the sample with
reagent mixture;
 at high concentration of chlorine dioxide (> 10 g/l) the samples shall be collected in a vessel, containing
water; the analytical result shall be corrected accordingly for the dilution factor;
 titration analysis shall best be carried out immediately after sampling plus reaction;
 if immediate titration or measurement is not possible, prior to the analytical measurements the sample
plus reagent shall be stored in the dark at low temperature about 5 °C and contact with ambient air shall
be avoided;
 if immediate collection and analysis are not possible, sample the reactor effluent in a 250 ml conical flask
stored on crushed ice and, by introducing the liquid at the bottom of the flask and fill the flask completely
allowing overflow of chlorine dioxide solution.
The volume of the samples shall be adjusted in accordance with the analytical procedure described hereafter.
5.2 Determination of chlorine dioxide and chlorite concentrations
5.2.1 General
This standard method concerns the determination of chlorine dioxide and chlorite concentrations in stored
solution.
NOTE Other oxidizing agents could interfere with the determination.
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5.2.2 Principle
5.2.2.1 General
Phosphate-buffered iodide is first reacted with the chlorine dioxide sample and titrated at pH 7,2 and
subsequently acidified to pH 2 and titration is continued.
5.2.2.2 With iodometry at pH 7,2
- -
ClO + l ⇒ ClO +1/2 l (1)
2 2 2
and
- -
Cl + 2 l ⇒ l + 2Cl (2)
2 2

5.2.2.3 Subsequent iodometry at pH 2
- - + -
ClO + 4 I + 4 H ⇒ Cl + 2 H O + 2 I (3)

2 2 2
The ratio of equivalents titrated at pH 7,2 and pH 2 shall be 1 to 4 within a deviation of less than 3 % and
indicate at least 97 % of the expected yield. If not appropriate, adjustments and an additional control as given
in 5.2.2.4 can be made, and more selective controls made occasionally according to the methods described in
A.3 and A.4.
5.2.2.4 Chlorite determination
Determination of chlorite concentration after degassing of a separate sample followed by iodometry at pH 2
(reaction is as in 5.2.2.3 and measure only the chlorite concentration of the sample). The degassing
procedure is given in A.4.1.
5.2.3 Reagents
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 in
accordance with EN ISO 3696:1995.
5.2.3.1 Sodium thiosulfate standard volumetric solution c(Na S O ) = 0,1 mol/l.
2 2 3
5.2.3.2 Phosphate buffer of pH = 7,2
Dissolve in 1 l of water, 28,2 g of sodium dihydrogen phosphate (NaH PO . 2H O) and 100 g monohydrogen

2 4 2
phosphate (Na HPO . 12H O).

2 4 2
NOTE If necessary, precise adjustment of the pH value can be done with aliquots of sodium hydroxide (NaOH) or
phosphoric acid (H PO ).
3 4
5.2.3.3 Sulfuric acid c(H SO ) = 6 mol/l.
2 4
5.2.3.4 Potassium iodate (KlO ) powdered.
3
5.2.3.5 Hydrochloric acid standard volumetric solution c(HCl) = 0,1 mol/l or sulfuric acid
c(H SO ) = 0,5 mol/l.
2 4
5.2.3.6 Potassium iodide, (Kl) crystalline.
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5.2.3.7 Zinc iodide (ZnI )-starch indicator.
2
Disperse 4 g starch into a small quantity of water. Add the dispersion to a solution of 20 g zinc chloride (ZnCl )
2
in 100 ml of water. The solution is boiled until the volume has been reduced to 100 ml and finally diluted to 1 l
while adding 2 g of ZnI .
2
NOTE An alternative starch indicator is soluble starch 5 g + ZnCl 4 g + salicylic acid 1,25 g; disperse the starch in a
2
small volume of water. Dissolve ZnCl and salicylic acid in 500 ml water, boil and, while boiling, add the starch dispersion.
2
Continue boiling for 5 min and finally dilute to 1 l.
5.2.3.8 Standardization of sodium thiosulfate solution
5.2.3.8.1 Reactions
+ +
5KI + 5H ⇒ 5Hl + 5K (4)
KlO + H+ ⇒ HlO + K+ (5)
3
3
HlO + 5Hl ⇒ 3I + 3H O (6)
3 2 2
2- - 2-
3I + 6S O ⇒ 6I + 3S O (7)
2 2 3 4 6
5.2.3.8.2 Determination
Add 0,05 g of potassium iodate (5.2.3.4), 0,5 g of potassium iodide (5.2.3.6) into 50 ml water and a further
50 ml water in a conical flask. After mixing, add 10 ml acid standard volumetric solution (5.2.3.5). Titrate the
liberated iodine immediately with the sodium thiosulfate solution (5.2.3.2) until the solution is pale yellow.
Add 0,5 ml of starch indicator (5.2.3.7) and titrate to the end point, i.e. the disappearance of the blue-black
colour. Record the volume V of the sodium thiosulfate solution added.
t
5.2.3.8.3 Calculation
The concentration, c , expressed in moles per litre, of the sodium thiosulfate solution is given by the following
t
equation:
c ×V
a
c = (8)
t
V
t
where
c is the concentration, in moles per litre, of the acid (5.2.3.5);
a
V is the volume, in millilitres, of the acid (5.2.3.5);
V is the volume, in millilitres, of the sodium thiosulfate solution used.
t
5.2.4 Apparatus
Ordinary laboratory apparatus:
 all glassware shall be dark brown to protect against photodecomposition;
 wash all glassware with a dilute solution (approximately 1 g/l) of chlorine dioxide and rinse with water; the
glassware used for the determinations of chlorine dioxide and related oxidants shall be reserved for this
specific use and kept maintained separately.
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5.2.5 Procedure
Prepare sets of three conical flasks of 250 ml immediately before the sampling: take 80 ml of water, followed
by 20 ml buffer solution (5.2.3.2) and approximately 1 g of potassium iodide (5.2.3.6). Use immediately or
keep in the dark if immediate use is not possible.
Introduce a volume (V ) of chlorine dioxide solution which (presumably) contains between 3 mg and 10 mg of
s
ClO .
2
Titration of sample under conditions of 5.2.2.2 gives a volume V of the sodium thiosulfate standard volumetric
1
solution (5.2.3.1). After this first titration add 5 ml of the sulfuric acid (5.2.3.3) and after shaking the titration is
continued to give an additional volume V of the sodium thiosulfate standard volumetric solution (5.2.3.1).
2
5.2.6 Expression of results
5.2.6.1 Calculation
The concentration of chlorine dioxide (Cs) expressed in milligrams per litre is given by the following equation:
(V +V )× c× 67,5×1 000
1 2
Cs= (9)
5×V
s
where
V is the volume in millilitres, of the sodium thiosulfate standard volumetric solution (5.2.3.1) used for the

1
titration at pH 7,2;
V is the volume in millilitres, of the sodium thiosulfate standard volumetric solution (5.2.3.1) used for the
2
titration at pH 2;
V is the volume in millilitres, of the test portion of chlorine dioxide;
s
c is the actual concentration, expressed in moles per litre, of the sodium thiosulfate standard
volumetric solution (5.2.3.1).
It is first to be verified that 4 × V = V with acceptable accuracy of 3 %. If not, the results are rejected and the
1

2
whole procedure shall be repeated, and/or, action shall be taken as indicated in 5.2.2.
5.2.6.2 Precision
Repeatability: 20 mg/l.
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6 Labelling - Storage - Distribution system
5)
6.1 Labelling according to the EU legislation
Labelling requirements in Table 3 shall apply to chlorine dioxide solution at the date of publication of this
document.
WARNING — Even solutions of chlorine dioxide at concentrations < 0,3 % can cause harmful gas
emissions. Therefore safety measures have to be followed accordingly (see Annex B).
Table 3 — Risk and safety labelling
Solutions of hydrogen peroxide concentration
C ≥ 5 % H314
H315
1 % ≤ C < 5 %
3 % ≤ C < 5 % H318
H319
0,3 % ≤ C < 10 %
C ≥ 3 % H335

5 ) See [3].
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Hazard pictogram
 Signal word : Danger
 Hazard statements :
H301 : Toxic if swallowed
H314 : Cause severe skin burns and eye damage
H315: Causes skin irritation
H318: Causes serious eye damage
H319: Causes serious eye irritation
H335: May cause respiratory irritation

Figure 1 — GHS05
H400 : Very toxic to aquatic life
NOTE Precautionary statements ('P statements') should be
provided by the company being responsible for the marketing of the
substance. They should be indicated on the packaging label and in the
extended safety data sheet (eSDS) of the substance.

Figure 2 — GHS06

Figure 3 —GHS09
The legislation [3], and its amendments for the purposes of its adaptation to technical and scientific progress
contains a list of substances classified by the EU. Substances not listed in this regulation 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.
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6.2 Means of distribution
For local short time storage of diluted solutions (e.g. less than 3 g/l, for less than 30 min, at pH value in the
range of 2,0 to 5,5 in operational conditions) and, also for generating equipment, appropriate materials are:
dark brown glass and borosilicate glassware, polyvinylchlorid (PVC), cross-linked HD-polyethylene,
polyfluorocarbons. "Chromium steels" and stainless steels are less suited for contact with chlorine dioxide.
Rubber and general plastics materials shall be proven specifically for resistance to chlorine dioxide.
6.3 Storage, stability
In aqueous solution, at dilutions between 0,5 g/l and 2 g/l, when stored in the dark, chlorine dioxide is stable
for several hours. Exposure to direct sunlight and heat shall be avoided. It is generally recommended to limit
the local storage to less than 30 min.
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Annex A
(informative)

General information on chlorine dioxide
A.1 Origin
A.1.1 Raw materials
Chlorine dioxide is produced from raw materials which fulfil the requirements as specified by the following
standards:
 Chlorine for water treatment: EN 937;
 Sodium hypochlorite for water treatment: EN 901;
 Hydrochloric acid for water treatment: EN 939;
 Sulfuric acid for water treatment: EN 899;
 Sodium chlorite for water treatment: EN 938;
 Sodium peroxodisulfate for water treatment: EN 12926;
 Potassium peroxomonosulfate for water treatment: EN 12678;
 Sodium chlorate for water treatment: EN 15028;
 Hydrogen Peroxide for water treatment: EN 902.
A.1.2 Manufacturing process
Numerous reactions to produce chlorine dioxide have been described and operated. For the scale of
production required for water treatment, the main reactions are:
NaClO + ½ H SO + ½ H O ⇒  ClO + ½ O + ½ Na SO + H O (A.1)
3 2 4 2 2  2 2 2 4 2
2 NaClO + Cl ⇒ 2 ClO + 2 NaCl (A.2)
2 2 2

NOTE Acidified hypochlorite can be used as an alternative source of chlorine.
and
5 NaClO + 4 HCl ⇒ 4 ClO + 5 NaCl + 2H O (A.3)
2 2 2
an alternative reaction is:
2 NaClO + Na S O ⇒ 2ClO + 2 Na SO (A.4)
2 2 2 8 2 2 4
All reactions are operated under controlled conditions and concentrations with process water in closed
reactors.
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Present available reactor designs according to the stoichiometry given above enable to produce chlorine
dioxide solutions with a yield of 90 % and higher. Residual impurities are traces of chlorate for reaction (A.1)
and chlorine and chlorite for reactions (A.2-A.4). The formation of chlorate for reactions (A.2)-(A.4) is avoided
by adequate reactor design, operating and pH control. More details are given in [5] and [6].
A.2 Use
A.2.1 Function
C
...