Reference number  
DRS 353 -3: 2018  
© RSB 2018  
 
 
 RWANDA 
STANDARD  DRS 
353-3 
 
First e dition  
2018 -mm-dd 
 
Water quality — Chemicals used for 
treatment of water intended for human 
consumption — 
Part 3: 
Sodium chlorate  
  DRS 353 -3: 2018  
©RSB 2018 - All rights reserved                  ii 
 In order to match with technological development and to keep continuous progress in industries, 
standards are subject to periodic review. Users shall ascertain that they are in possession of the latest 
edition  
 
 
 
 
 
 
 
 
© RSB 2018  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized 
in any form or by any means, electronic or mechanical, including photocopying and microfilm, without 
prior written permission from R SB. 
Requests for permission to reprodu ce this document should be addressed to : 
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
KK 15 Rd, 49  
Tel. +250 788303492  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw   
ePortal: www.portal.rsb.gov.rw   DRS 353 -3: 2018  
iii                ©RSB 2018 - All rights reserved  
 Contents  Page 
1 Scope  ................................ ................................ ................................ ................................ .............  1 
2 Normative references  ................................ ................................ ................................ ...................  1 
3 Desc ription  ................................ ................................ ................................ ................................ .... 1 
3.1 Identification  ................................ ................................ ................................ ................................ . 1 
3.2 Commercial forms  ................................ ................................ ................................ ........................  2 
3.3 Physical properties  ................................ ................................ ................................ ......................  2 
3.4 Chemical properties  ................................ ................................ ................................ .....................  3 
4 Purity criteria  ................................ ................................ ................................ ................................  3 
4.1 General  ................................ ................................ ................................ ................................ ..........  3 
4.2 Composition of commercial product  ................................ ................................ ..........................  4 
4.3 Impurities and main by -products  ................................ ................................ ................................  4 
5 Labelling, transportation and storage  ................................ ................................ ........................  4 
5.1 Means of delivery  ................................ ................................ ................................ .........................  4 
5.2 Mark ing ................................ ................................ ................................ ................................ ..........  5 
5.3 Transportation  ................................ ................................ ................................ ..............................  5 
5.4 Storage  ................................ ................................ ................................ ................................ ..........  5 
5.5 Labelling  ................................ ................................ ................................ ................................ ........  6 
Annex  A (normative)  General rules relating to safety  ................................ ................................ ..........  7 
A.1 Rules for safe handling and use  ................................ ................................ ................................ . 7 
A.2 Emergency procedures ................................ ................................ ................................ ................  7 
Anne x B (informative)  General information on sodium chlorate  ................................ ........................  8 
B.1 Origin  ................................ ................................ ................................ ................................ .............  8 
B.2 Use ................................ ................................ ................................ ................................ .................  8 
Annex  C (informative)  Environmental, health and safety precautions within chemical 
laboratory  ................................ ................................ ................................ ................................ .... 10 
Annex  D (informative)  Recommended test methods  ................................ ................................ ..........  11 
D.1 Test methods  ................................ ................................ ................................ ..............................  11 
 DRS 353 -3: 2018  
©RSB 2018 - All rights reserved                  iv 
 Foreword  
Rwanda Standard s are prepared  by Technical Committees and approved by R wanda Standards Board (RSB) 
Board  of Directors in  accordance with t he procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task of technical committees is to prepare national standards.  Final Draft Rwanda S tandards adopted 
by Technical committ ees are ratified  by me mbers of RSB Board of Director s for publication and gazettment as 
Rwanda Standards.  
DRS 353-3 was prepared by Technical Committee RSB/TC 013, Water and sanitation  
In the preparation of this standard, reference was made to the f ollowing standard:  
BS EN 15028: 2012, Chemicals used for treatment of water intended for human consumption — Sodium 
chlorate  
The assistance de rived from the above source is hereby acknowledged with thanks.  
DRS 353 consists of the following  parts, under the general title Water quality — Chemicals used for treatment 
of water intended for human consumption : 
 Part 1: Aluminium sulphate  
 Part 2: Calcium hypochlorite  
Part 3: Sodium chlorate  
Committee membership  
The following organizations were represented on the Technical Committee on Water and sanitation  (RSB/TC 
013) in the preparation of this standard.  
Integrated Polytechnic Regional Centre/Kigali (IPRC -Kigali)  
Rwanda Utility Regulatory Authority (RURA)  
TAI Con sult Ltd  
University of Rwanda/College of Sciences and Technology (UR/CST)  
Water and Sanitation Corporation Ltd (WASAC)  
Rwanda  Standards Board  (RSB) – Secretariat  DRS 353 -3: 2018  
v                ©RSB 2018 - All rights reserved  
 Introduction  
Treatment of water intended for human consumption can be achieved by using various chemicals which might 
raise the risk of cancer or cause other health hazards by creating toxic by -products that need tighter control in 
order to avoid those risks and meets requirements of drinking water as stated in RS EAS 153.  
Chemicals used duri ng treatment of water have to be of good quality and meet standards requirement, in order 
to avoid any contamination of water by impurities of these chemicals and therefore ensure a successful water 
treatment.  
 DRS 353 -3: 2018  
1                ©RSB 2018 - All rights reserved  
 Water quality — Chemicals used for water intended for human 
consumption  — Part 3: Sodium chlorate  
1 Scope  
This Rwandan Standard describes the characteristics of sodium chlorate and specifies the requirements and 
the corresponding test methods for sodium chlorate. It gives information on its use in water treatment. It also 
determines the rules relating to safe handling and use of sodium chlorate and gives the environmental, health 
and safety precautions within chemical laboratory.  
This standard is applicable to sodium chlorate used for treatment of water intended for human consumption.  
2 Normative references  
The following documents are referred to i n 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) app lies. 
ISO 3696 , Water for analytical laboratory use — Specification and test methods  
ISO 11885 , Water quality — Determination of selected elements by inductively coupled plasma optical emission 
spectrometry  
ISO 3165 , Sampling of chemical products for industrial use — Safety in sampling  
3 Description  
3.1 Identification  
3.1.1  Chemical name  
Sodium chlorate  
3.1.2  Synonym or common names  
None ( for the processes related to treatment of drinking water)  
Note  names of formulations might exist. Purity needs to be checked in case of use for treatment of water.  
3.1.3  Relative molecular mass  
106.45  
3.1.4  Empirical formula  
NaClO 3 
3.1.5  Chemical formula  
NaClO 3  
©RSB 2018 - All rights reserved                  2 
 3.2 Commercial forms  
Sodium chlorate is commercially available in crystalline form or as a powder and as an aqueous solution.  
3.3 Physical properties  
3.3.1  Appearance and odour  
The product is a colourless or white solid as a powder or the product is a faint blue to colourless solution. Sodium 
chlorate is odourless.  
3.3.2  Density  
The density of an aqueous solution of sodium chlorate is given in Table 1.  
Table 1 — Densi ty of sodium chlorate solution  
Concentration of aqueous solution of sodium 
chlorate solution  
(Mass fraction in %)  Density (g/ml at 20 °C)  
30 1.24 
40 1.33 
50 1.44 
 
3.3.3  Solubility in water  
The solubility of sodium chlorate in water is given in Table 2.  
Table 2 — Solubility of sodium chlorate at 100kPa  
Temperature  
(°C)  Solubility  
(g/l)  
10  650  
20  700  
40  780  
60  880  
3.3.4  Boiling point at 100 kPa  
The boiling point of aqueous solutions of sodium chlorate is given in Table 3.  
Table 3 — Boiling point at 100 kPaof aqueous solutions of sodium chlorate  
Concentration of aqueous solution of sodium 
chlorate (g NaClO 3 /kg of saturated solution)  400 450 500 550 600 650 700 
Boiling point (°C)  106 107 109 110 111 113 116 
 DRS 353 -3: 2018  
3                ©RSB 2018 - All rights reserved  
 3.3.5  Crystallisation  
The crystallisation point of aqueous solutions of sodium chlorate depending on concentration in water is given 
in Table 4.  
Table 4 – Crystallisation point of sodium chlorate aqueous solutions  
Concentration of aqueous solution of sodium chlorate 
(mass frac tion in %)  Crystallisation point (°C)  
40 -20 
45 0 
50 20 
55 32 
60 55 
3.3.6  Melting point  
The melting point (of the solid) is 248 °C; and the thermal decomposition is at ≥ 400 °C.  
3.3.7  Viscosity (dynamic)  
The relative viscosity of aqueous solutions of mass fraction of 40 % of sodium chlorate compared with water at 
the same temperature between 25 °C and 35 °C is 2.07.  
3.4 Chemical properties  
The sodium chlorate is a strong oxidising agent.  
Note 1  When an acidic sodium chlorate solution is treated with a reducing agent (e.g. hydrogen peroxide or oxalic acid), 
chlorine dioxide can be formed.  
Note 2  The formation of chlorine dioxide can also be obtained by acidification if the acid applied is capable  of acting as 
a reducing agent in the current environment.  
 
4 Purity criteria  
4.1 General  
4.1.1  This Standard specifies the minimum purity requirements for sodium chlorate used for the treatment of 
water intended for human consumption. Limits are given for impu rities commonly present in the product. 
Depending on the raw material and the manufacturing process other impurities can be present and, if so, this 
shall be notified to the user and when necessary to relevant authorities.  
Note  Users of the product should  check the national regulations in order to clarify whether it is allowed/not 
banned and is of appropriate purity for treatment of water intended for human consumption, taking into account 
raw water quality, required dosage, contents of other impurities an d additives used in the product not stated in 
the product standard, and other relevant factors.   
©RSB 2018 - All rights reserved                  4 
 4.2 Composition of commercial product  
The sodium chlorate is commercially available as solid forms usually with a minimum dry mass fraction of 99 % 
of NaClO 3.  
Comm ercial solutions if used for water treatment shall be certified to be made -up on the basis of the product 
with a dry mass fraction of 99 %. No additional substances like colorants shall be added to the basic product or 
to the solutions.  
The content of sod ium chlorate in commercially available solutions shall be within 3 % (error) of the 
manufacturer's declared value.  
4.3 Impurities and main by -products  
Sodium chlorate in crystalline form contains normally a maximum mass fraction of 0.1 % of sodium chloride (as  
NaCl).  
The product shall conform to the requirements specified in Table 5.  
Table 5 — Other impurities  
Parameter  
  
 Limit in sodium chlorate (mass fraction 
100%  
mg/kg  
Arsenic (As)  max.  1 
Cadmium (Cd)  max.  1 
Chromium (Cr)  max.  5 
Mercury (Hg)  max.  1 
Nickel (Ni)  max.  1 
Lead (Pb)  max.  1 
Antimony (Sb)  max.  1 
Selenium (Se)  max.  1 
NOTE:Cyanide, which does not exist in a strong oxidizing medium such as sodium chlorate is not a 
relevant chemical parameter. Pesticides and polycyclic aromatic hydrocarbons are not by -products of the 
manufacturing process.  
5 Labelling, transportation and storage  
5.1 Means of delivery  
Sodium chlorate crystals shall be delivered in bags or bulk containers made of stainless materials.  
Aqueous solutions of sodium chlorate shall be delivered in polyethylene or stainless steel containers or tankers. 
capacity of container shall be in accordance with national regulations.  
The means of delivery shall not have been used previously for any dif ferent product or it shall have been 
specially cleaned and prepared before use.  DRS 353 -3: 2018  
5                ©RSB 2018 - All rights reserved  
 5.2 Marking  
The following marking requirements shall apply to sodium chlorate.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
5.3 Transportation  
National regulations on transportation of chemicals and dangerous products shall apply. When authorised by 
competent authority, the application of appropriate  international regulations on transportation of dangerous 
goods may apply.  
5.4 Storage  
5.4.1  General  
The product shall be stored in suitable containers used exclusively for sodium chlorate. It shall be stored away 
from direct sunlight, in a cool, well -ventilated area, but at a temperature not lower than the crystallisation point 
(see 3.3.6).  
5.4.2  Long term stability  
The product is relatively stable for a period of one year.  
Note  After that period the user should verify the stability of the product.  
5.4.3  Storage incompatibilities  
The product shall not be allowed to come into contact with acids, combustible material or organic compounds 
(e.g. wood, paper and grease).  
 
 
 
Signal word:  
Danger  
Hazard statement:  
May intensify fire; Oxidizer  
Harmful if swallowed  
Very toxic to aquatic life  with long 
lasting effects   
©RSB 2018 - All rights reserved                  6 
 5.5 Labelling  
The labelling shall include the following information:  
 name: “ sodium chlorate ” trade name and grade;  
 net mass;  
 density/concentration  
 name and the address of the supplier and/or manufacturer; and  
 statement of conformity to the standard ”. 
 Shelf life  
 Storage conditions  
 Batch number   
The supplier shall provide a certificate of analysis against the standards  
NOTE  The user should verify the relevance of that certificate  
 
 
 
 DRS 353 -3: 2018  
7                ©RSB 2018 - All rights reserved  
 Annex  A 
(normative)  
 
General rules relating to safety  
A.1 Rules for safe handling and use  
The supplier shall provide current safety instructions.  
A.2 Emergency procedures  
A.2.1  General  
Textile, cellulose or leather contaminated with dried sodium chlorate ignites easily.  
A.2.2  First aid  
Keep clothing contaminated with sodium chlorate wet, remove as quickly as possible and wash or immerse in 
water before it dries.  
In case of inhalation remove to fresh air. Seek medical care immediately if toxic symptoms occur.  
In case of contact with the skin wash skin with soap and water.  
In case of contact with the eyes rinse immediately with water. Seek medical care if symptoms remain.  
In case of ingestion rinse mouth and drink immediately two or more glasses of water or milk. Do not induce 
vomiting. Seek medical care if more than a negligible amount has been swallowed.   
A.2.3  Spillage  
Rinse with plenty of water.  
Textile, cellulose or leather contaminated with dried sodium chlorate ignites easily.  
If used in closed rooms, foresee preventive venting.  
A.2.4  Fire  
Use water as extinguishing medium. Do not use powder or CO2 -type ext inguisher.  
 
  
©RSB 2018 - All rights reserved                  8 
 Annex  B 
(informative)  
 
General information on sodium chlorate  
B.1 Origin  
B.1.1  Raw materials  
Sodium chlorate is manufactured from sodium chloride (NaCl ). 
B.1.2  Manufacturing process  
It is produced by an electrochemical process in which sodium chloride is converted to sodium chlorate and 
hydrogen (H2).  
B.2 Use 
B.2.1  Function  
Its function in water treatment is mainly the generation of chlorine dioxide by reaction with a reducing agent in 
acid m edium. It can also be temporarily used directly for the cleaning/maintenance of premises; in such case it 
is mostly not dosed directly in the drinking water.  
B.2.2  Form in which it is used  
It is used as delivered or as a pre -blended aqueous solution.  
B.2.3  Treatment  dose  
The treatment dose depends on the composition of the raw water. Care should be taken not to exceed the 
general allowed residuals.  
B.2.4  Means of application  
It is applied using a metering -pump for aqueous solutions or by means of a chlorine dioxide gene rator.  
B.2.5  Secondary effects  
The secondary effects include the following:  
 oxidation of iron, manganese ; 
 Odour and colour removal;  DRS 353 -3: 2018  
9                ©RSB 2018 - All rights reserved  
  Oxidation of organic compounds  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
©RSB 2018 - All rights reserved                  10 
 Annex  C 
(informative)  
 
Environmental, health and safety precautions within chemical laboratory  
When preparing the analytical methods for application of this European Standard consideration was given to 
the minimisation of environmental impacts caused by the use of the methods of analysis.  
It is the user’s responsibility to use s afe and proper techniques in handling materials in the methods of analysis 
specified in this document.  
The following list is not exhaustive but users of the analytical methods referred in this European Standard may 
use it as a guide to the use of safe and  proper techniques. They should:  
 Investigate if national legislation and laws, regulations and administrative provisions apply;  
  Consult manufacturers / suppliers for specific details such as material safety data sheets and other 
recommendations;  
 Use saf ety equipment and wear protective clothing, usually goggles and coats, appropriate for the test 
product and the test chemicals, in all laboratory areas, to ensure the safety of the operator;  
  Be careful about flammable materials and substances that are tox ic and/ or human carcinogens and 
generally take care during transportation, decanting, diluting and dealing with spillages;  
  Use a fume cupboard during preparation of organic solvent solutions;  
Store, handle and dispose of chemicals in a safe and environmentally satisfactory manner: including 
chemicals for laboratory test, test specimens, unused solvents and reagents that have to be disposed of.  DRS 353 -3: 2018  
11                ©RSB 2018 - All rights reserved  
 Annex  D 
(informative)  
 
Recommended test methods  
D.1 Test methods  
D.1.1  Sampling  
D.1.1.1  General  
Observe the general recommendatio ns of ISO 3165 and take into account ISO 6206  
D.1.1.2  Solid  
Prepare the laboratory sample(s) required by the relevant procedure described in ISO 8213.  
D.1.1.3  Liquid  
D.1.1.3.1  Sampling from drams and bottles  
D.1.1.3.1.1  General  
D.1.1.3.1.1  Mix the contents of each container to be sampled by sh aking 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.  
D.1.1.3.1.2  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 D.1.1.3.1.3.  
D.1.1.3.1.3  Examine the surface of the liquid. If there are signs of surface contamination, take samples 
from the surface as described in D.1.1.3.1.2. Otherwise, take samples as described in D.1.1.3.1.3.  
D.1.1.3.1.2  Surface sampling  
Take a sample using a suitable ladle. Lower the ladle into the liquid until the rim is just below the surface, so 
that the surface layer runs int o 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 sam ple required for subsequent analysis is obtained.  
D.1.1.3.1.3  Bottom sampling  
Take a sample using an open sampling tube, or a bottom -valve sampling tube, suited to the size of container 
and the viscosity of the liquid.  
When using an open sampling tube, close it at the  top and then lower the bottom end to the bottom of the 
container. Open the tube and move it rapidly so that the bottom of the tube traverses the bottom of the container 
before the tube is filled. Close the tube, withdraw it from the container and allow an y liquid adhering to the 
outside of the tube to drain off.   
©RSB 2018 - All rights reserved                  12 
 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.  
D.1.1.3.2  Sampling from tan ks and tankers  
From each access point, take samples as follows:  
a) from the surface of the liquid, using a ladle as described in D.1.1.3.1.2;  
b) from the bottom of the tank or tanker, using a sampling tube as described in D.1.1.3.1.3 or using a specially 
designed bottom -sampling apparatus;  
From one or more positions, depending on the overall depth, between the bottom and the surface using a 
weight ed sampling can.  
D.1.2  Analysis  
D.1.2.1  Determination of sodium chlorate (main product)  
D.1.2.1.1  General  
This method is valid for determination of sodium chlorate in products containing sodium chlorate exclusively, 
mainly as a solid made up in solution for analytical purposes.  
D.1.2.1.2  Principle  
Chlorate ion is reduced by excess of iron (II) by heating at low pH. Remaining iron (II) is determined titrimetrically 
with chromium (VI).  
Reactions:   
ClO 3- + 6 e- + 6 H+ → Cl- + 3 H 2O  
Fe2+→ Fe3+ + e- 
Cr2O72- + 14 H+ + 6 e-→ 2 Cr3++ 7 H 2O. 
D.1.2.1.3  Reagents  
All reagents shall be of a recognised analytical grade and the water used shall conform to grade 3 in accordance 
with ISO 3696.  
D.1.2.1.3.1  Mixed acid solution.  
Add 150 ml concentrated sulfuric acid and 150 ml concentrated phosphoric acid slowly in 700 ml wa ter while 
cooling.  
D.1.2.1.3.2  Iron (II) ion solution, 0,23 mol/l  
Dissolve 75,2 g of ammonium iron (II) sulfate hexahydrate ((NH 4)2Fe(SO 4)2.6H 2O) in 1 l of sulfuric acid solution 
at 1 mol/l.  DRS 353 -3: 2018  
13                ©RSB 2018 - All rights reserved  
 This solution is used without further standardization.  
D.1.2.1.3.3  Indicators  
Weigh 0,20  g of sodium diphenylamine sulfonate indicator and place in a 100 ml volumetric flask. Add 50 ml 
water to dissolve the indicator, followed by 5 ml of mixed acid (D.1.2.1.3.1). Make up to the mark with water.  
D.1.2.1.3.4  Potassium dichromate solution, c(K2Cr2O7) =0,05 mol/l (primary standard)  
Dry potassium dichromate (K 2Cr2O7) crystals (primary standard or analytical grade) between 140 °C and 180 °C 
for 30 min to 60 min. Weigh 13,82 g of dry K 2Cr2O7, place into a 1 000 ml volumetric flask and add water to 
approximately 750 ml. Dissolve and make up to the mark with water. Pour into a clean, dry container.  
D.1.2.1.4  Apparatus  
Ordinary laboratory apparatus and glassware, together with the following:  
D.1.2.1.4.1  Titration apparatus, a manual titrator or a titroprocessor with redox electrode  
D.1.2.1.4.2  balance (0,1 mg accuracy)  
D.1.2.1.4.3  Weighing glasses, small 5.2.1.4.4  Hotplate  
D.1.2.1.5  Procedure  
D.1.2.1.5.1  General  
Prepare samples and a blank.  
D.1.2.1.5.2  Test portion  
Weigh, to the nearest 0,1 mg, a test portion ( m) containing between 0,2 g and 0,3 g of the sodium chlorate in 
solution into a weighing glass (D.1.2.1.4.3).  
D.1.2.1.5.3  Determination  
Transfer the test portion (D.1.2.1.5.2) to a 250 ml conical flask containing 50 ml iron (II) solution (D.1.2.1.3.2) 
and 20 ml of mixed acid solution (D.1.2.1.3.1).  
Heat t o boil,  
Add 150 ml of water and 10 drops of indicator (D.1.2.1.3.3) to the solution.  
Titrate with the potassium dichromate solution (D.1.2.1.3.4) to the end point, the colou r changes from green to 
purple.  
Record the volume Vx for the test solution end po int and the volume Vy for the blank test solution end point. The 
blank test solution volume, Vy, is approximately 40,5 ml and the volume Vx is approximately 8,5 ml for 0,40 g of 
mass fraction of 40 % NaClO 3 solution.  
D.1.2.1.6  Expression of results  
The sodium chlor ate (NaClO 3) content, C1, expressed as mass fraction in %, is given by the following formula:   
©RSB 2018 - All rights reserved                  14 
 𝑪𝟏=(𝑽𝐲−𝑽𝐱)×𝑪𝑲𝟐𝑪𝒓𝟐𝑶𝟕×𝐌×𝟏𝟎𝟎
𝐦×𝟏𝟎𝟎𝟎= (𝑽𝐲−𝑽𝐱)×𝟎,𝟓𝟎𝟎
𝐦 (1) 
where  
Vy is the volume, in millilitres, of potassium dichromate solution (5.2.1.3.4) used for titration at the end point 
for the blank test solution;  
Vx is the volume, in millilitres, of potassium dichromate solution (5.2.1.3.4) used for titration at the end poin t 
for the test solution sample;  
𝑪𝑲𝟐𝑪𝒓𝟐𝑶𝟕 is the concentration of the potassium dichromate solution (5.2.1.3.4), 0,046 97 mol/l;  
m is the mas s in grams of the test portion;  
M is the molar mass of sodium chlorate ( M = 106,441).  
Express the result with one decimal.  
For certification of the product at least three samples shall be analyzed in parallel and the results shall be found 
consistent within a standard deviation of mass fraction of 0,004 %.  
D.1.2.2   Chemical parameters  
D.1.2.2.1  Determinatio n of antimony (Sb), arsenic (As), cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni) 
and selenium (Se)  
D.1.2.2.1.1  Principle  
The elements arsenic, antimony, cadmium, chromium, lead, nickel and selenium are determined by inductively 
coupled plasma optical emission sp ectrometry (ICP/OES).  
D.1.2.2.1.2  Reagents  
All reagents shall be of a recognised analytical grade and the water used shall conform to the grade 3 specified 
in ISO 3696 . 
D.1.2.2.1.2.1  Nitric acid, concentrated, density ρ = 1,42 g/ml.  
D.1.2.2.1.2.2  As, Cd, Cr, Ni, Pb, Sb and Se element, stock solution, c(element) = 1 000 mg/l commercial 
solution.  
D.1.2.2.1.2.3  Yttrium, internal standard, solution, c(Y) = 100 mg/l.  
Prepare this solution by adding 10,00 ml of yttrium solution c (Y) = 1 000 mg/l to a 100 ml volumetric flas k.  
Add 1 ml concentrated nitric acid (D.1.2.2.1.2.1). Make up to the mark with water.  
D.1.2.2.1.3  Procedure  
D.1.2.2.1.4  Test portion  
Weigh, to the nearest 0,001 g, 10,0 g of sodium chlorate crystals or 20,0g of a solution of a known amount of 
sodium chlorate into a 100 ml volum etric flask.  DRS 353 -3: 2018  
15                ©RSB 2018 - All rights reserved  
 D.1.2.2.1.5  Test solution  
To the test portion (D.1.2.2.1.3.1) add 10,00 ml of the yttrium solution (D.1.2.2.1.2.3) and 0,5 ml of nitric acid 
(D.1.2.2.1.2.1) and make up to 100 ml with water.  
D.1.2.2.1.6  Determination  
Determine the content of the elements in the tes t solution (D.1.2.2.1.3.2) in accordance with ISO 11885 .  
In addition to the determination carried out with ISO 11885  allow to add 10 mg/l of y ttrium to reagent blank 
solution and to all reference solutions. Calibrate the instrument using yttrium as internal standard. The yttrium 
wavelengths are 371 nm or if not available 224 nm.  
This method is providing an interim result ( y) expressed in milligrams per litre which needs to be converted to 
give the final concentration according to the formula in D.1.2 .2.1.4.  
D.1.2.2.1.7  Expression of results  
From the interim result (y) determined (see D.1.2.2.1.3.3), the content, C 2, of each element in the laboratory 
sample, expressed in milligrams per kilogram of sodium chlorate of mass fraction 100 % is given by the following 
formula:  
𝑪𝟐=𝐲×𝑽×𝟏𝟎𝟎
𝐦×𝑪𝟏 (2) 
Where  
Y is the interim result (D.1.2.2.1.3.3);  
V is the volume, expressed in millilitres, of the test solution (D.1.2.2.1.3.2) (= 100 ml);  
M is the mass, expressed in grams, of the test portion;  
C1 is the content of the  sodium chlorate in mass fraction in % (D.1.2.1.6).  
D.1.2.2.2  Determination of mercury content (Hg)  
D.1.2.2.2.1  Principle  
The element mercury is determined by flameless atomic absorption spectrometry in accordance with ISO  12846.  
D.1.2.2.2.2  Reagents  
All reagents shall be of a recognised analytical grade and the water used shall conform to the grade 3 specified 
in ISO 3696.  
D.1.2.2.2.2.1  Potassium permanganate solution, c(KMnO4) = 50 g/l.  
D.1.2.2.2.2.2  Sulfuric acid, concentrated, density p = 1,84 g/ml.  
D.1.2.2.2.2.3  Hydroxylammonium chloride, c(NH2OH·HCl) = 100 g/l.  
D.1.2.2.2.2.4  Potassium dichromate solution, c(K2Cr2O7) = 4 g/l in volume fraction 50 % nitric acid solution.   
©RSB 2018 - All rights reserved                  16 
 D.1.2.2.2.3  Procedure  
D.1.2.2.2.4  Test portion  
Weigh 10,0 g of sodium chlorate crystals or pipette 20,0 g of a soluti on containing sodium chlorate of content 
C1 into a 100 ml volumetric flask. Make up to the mark with water and mix (solution A).  
D.1.2.2.2.5  Test solution  
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 (D.1.2.2.2.2.1) and five 1 ml portions of sulfuric acid (D.1.2.2.2.2.2). Heat and 
keep boiling for 10 min. Allow to cool. Dissolve the precipitate (MnO 2) with hydroxylammonium chloride 
(D.1.2.2.2.2.3), add 5 ml of the potass ium dichromate solution (D.1.2.2.2.2.4) and transfer to a 100 ml ( VT) 
volumetric flask. Make up to the mark with water and mix.  
D.1.2.2.2.6  Determination  
Proceed as described in ISO 12846 . 
D.1.2.2.2.7  Expression of results  
The interim result for mercury content (y) expressed in m illigrams per litre is given by the following formula:  
𝐲=𝐲𝐀×𝑽𝐓
𝟏𝟎 (3) 
Where, 
yA is the result obtained, for the concentration of mercury in solution A, expressed in milligrams per litre;  
VT is the volume in millilitres of the test solution.  
The content of mercury, C2, in milligrams per kilogram of sodium chlorate with mass fraction of   100 % is given 
by the formula:  
𝐂𝟐=𝐲×𝟏𝟎
𝐦𝟑×𝟏𝟎𝟎
𝐂𝟏 (4) 
where, 
m3 is the mass expressed in grams, of the test portion;  
C1 is the content of sodium chlorate  in mass fraction in % (D.1.2.1.6).  DRS 353 -3: 2018  
17                ©RSB 2018 - All rights reserved  
 Bibliography  
[1] EN 899, Chemicals used for treatment of water intended for human consumption — Sulfuric acid  
[2] EN 902, Chemicals used for treatment of water intended for human consumption — Hydrogen peroxide  
[3] EN 939, Chemicals  used for treatment of water intended for human consumption — Hydrochloric acid  
[4] EN 974, Chemicals used for treatment of water intended for human consumption — Phosphoric acid  
 DRS 353 -3: 2018  
ICS 71.100. 80 
 
 
©RSB 2018 - All right s reserved