Reference number  
DRS  353-2: 2017  
© RBS yyyy 
© RSB 2017  
 
 RWANDA 
STANDARD  DRS  
353-2 
 
First e dition  
2017 -mm-dd 
 
Water quality  — Chemicals used for 
treatment of water intended for human 
consumption  
Part 2: 
Calcium hypochlorite  
  DRS  353-2: 2017  
©RSB 2017 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  
 
 
 
 
 
 
 
 
 
 
© RSB2017  
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 reproduce this document should be addressed to  
Rwanda Standards  Board  
P.O Box 7099 Kigali -Rwanda  
Tel. +250 252 586103/ 582945  
Toll Free: 3250  
E-mail: info@rsb.gov.rw  
Website: www.rsb.gov.rw  DRS 353 -2: 2017  
iii                 ©RSB2017  All rights reserved  
 
 Contents  Page 
1 Scope  ................................ ................................ ................................ ................................ ......................  1 
2 Normative references  ................................ ................................ ................................ ............................  1 
3 Desc ription  ................................ ................................ ................................ ................................ .............  1 
4 Purity criteria  ................................ ................................ ................................ ................................ .........  2 
5 Labelling - Storage  ................................ ................................ ................................ ................................  5 
Annex  A (normative)  General rules relating to safety  ................................ ................................ ...................  7 
Annex  B (informative)  Determination of arsenic, antimony and selenium (atomic absorption 
spectrometry hydride technique)  ................................ ................................ ................................ ........  8 
Annex  C (informative)  General information on calcium hypochlorite  ................................ .......................  15 
Annex  D (informative)  Recommended test methods  ................................ ................................ ...................  17 
Annex  E (informative)  Environmental, health and safety precautions within chemical laboratory  ....... 26 
 DRS  353-2: 2017  
©RSB 2017 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 the procedures of RSB, in compliance with Annex 3 of the WTO/TBT 
agreement on the preparation, adoption and application of standards.  
The main task o f 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 -2 was prepared by Technical Committee RSB/TC 013, Environment, Health and Safety . 
In the preparation of this standard, reference was made to the following standard:  
BS EN 900 ,Chemicals used for treatment of water intended for human consumption — calcium hypochlorite  
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 sulfate  
 Part 2: Calcium hypochlori te 
Part 3: Sodium chlorate  
  DRS 353 -2: 2017  
v                 ©RSB2017  All rights reserved  
 
 Committee membership  
The following organizations were represented on the Technical Committee on Environment, Health and Safety  
(RSB/TC 013) in the preparation of this standard.  
Integrated Polytechnic Regional Centre  – Kigali ( IPRC -Kigali)  
Inyange Industries Ltd  
National Industrial Research and Development Agency (NIRDA)  
Rwanda Natural Resource Authority (RNRA)  
Star Construction & Consultancy (SCC)  
University of Kibungo (UNIK)  
Water and Sanitation Corporation (WASAC)  
Rwanda  Standards Board (RSB) – Secretariat  DRS  353-2: 2017  
©RSB 2017 All rights reserved                  vi 
 
 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 during treatment of water have to be of good quality and meets standards requirement, in 
order to avoid any contamination of wate r by impurities of these chemicals and therefore ensure a successful 
water treatment.  
 DRS 353 -2: 2017  
1                 ©RSB2017  All rights reserved  
 
 Water quality — Chemicals used for treatment of water intended for 
human consumption  — Part 1: Calcium hypochlorite  
1 Scope  
This Draft Rwanda Standard describes the characteristics of calcium hypochlorite and specifies the 
requirements and the corresponding test methods for  calcium hypochlorite. It provides information on its use 
in water treatment. It also determines the rules relating to safe handling and use of calcium hypochlorite . 
This document is applicable to calcium hypochlorite used for the treatment of water intended for human 
consumption.  
2 Normative references  
The following referenced documents are indispensable for the application of this document. For dated 
references, only the edition cited applies. For undated references, the latest edition of the referenc ed 
document (including any amendments) applies.  
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  
Calcium hypochlorite.  
3.1.2  Synonym or common names  
None.  
3.1.3  Relative molecular mass  
142,99.  
3.1.4  Empirical formula  
Ca(ClO) 2. 
3.1.5  Chemical formula  
Ca(ClO) 2.  
©RSB 2017 All rights reserved                  2 
 
 3.2 Commercial forms  
The product is available as a granular solid or in the form of tablets.  
3.3 Physical properties  
3.3.1  Appearance  
The p roduct is white free -flowing granules or white tablets.  
3.3.2  Density  
The bulk density is approximately 0,8 g/cm to 1 g/cm3 for loose granular material and 1,2 g/cm3 to 1,3 g/cm3 
for tablets, while the density of one tablet is approximately 1,7 g/cm3 to 1,9 g/cm3. 
3.3.3  Solubility in distilled water  
The solubility is 180 g/l at 25 °C.  
3.4 Chemical properties  
3.4.1  Solutions of calcium hypochlorite are alkaline. The pH value of a solution of concentration  10 g/l is 
about 11,5 at 25 °C.  
3.4.2 Calcium hypochlorite is a strong  oxidant and chlorination agent. It reacts with acids or acidic salts to 
form chlorine, and can form explosive nitrogen chlorides with ammonia and ammonia compounds. In the 
presence of inflammable substances, it causes fires and explosions of organic compo unds, oxidation 
reactions occur with the release of heat and of moisture, and it is also highly corrosive to most metals.  
4 Purity criteria  
4.1 General  
4.1.1  This Standard specifies the minimum purity requirements for calcium hypochlorite 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 manufact uring process other impurities may be present and if 
so, then the user, and when necessary the relevant authorities, shall be notified.  
4.1.2  Users of the product sh all 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 and additives used in the product not 
stated in the product standard, and other relevant f actors.  DRS 353 -2: 2017  
3                 ©RSB2017  All rights reserved  
 
 4.2 Composition of commercial product  
4.2.1  The product shall contain a minimum of a mass fraction of 65,5 % of calcium hypochlorite (equivalent 
to an available active chlorine content of at least a mass fraction of 65 %).  
4.2.2  Dissolution quality, ca lculated as available chlorine which is obtainable within 1 min after dissolution in 
water, shall not be less than a mass fraction of 45,5 % . 
4.2.3  The water content at the time of delivery sh all not exceed a mass fraction of 16 % of the product. As 
the te st method is usually not conducted by the user without danger of explosion, the manufacturer sh all 
guarantee to maintain this value. If necessary,  a test laboratory shall be requested to carry out this test. This 
determination sh all be carried out by speci alists only . 
 
4.3 Impurities and main by -products  
The content of water -insoluble matter shall not exceed a mass fraction of 6 % of the product.  
NOTE 1:  The water insoluble matter consists mainly of carbonates.  
NOTE 2:  Calcium chlorate can be present as a b y-product of the production process . 
   
©RSB 2017 All rights reserved                  4 
 
 4.4 Chemical parameters  
The product shall conform to the requirements specified in Table 1.  
Table 1 — Chemical parameters  
Parameter  
  
 Limit (mg/kg ) 
Type 1  Type 2  
Arsenic (As)  max.  5 10 
Cadmium (Cd)  max.  5 10 
Chromium (Cr)  max.  15 15 
Mercury (Hg)  max.  5 7 
Nickel (Ni)  max.  8 10 
Lead (Pb)  max.  15 15 
Antimony (Sb)  max.  15 15 
Selenium (Se)  max.  20 20 
  Limit in g/kg of available chlorine  
Bromate a  max.  2,1 4,2 
NOTE  Cyanide, which does not exist in a strong oxidizing medium such as calcium hypochlorite is not a relevant 
chemical parameter. Pesticides and polycyclic aromatic hydrocarbons are not by -products of the manufacturing process.  
a Bromate is a by -product of t he manufacturing process.  
  DRS 353 -2: 2017  
5                 ©RSB2017  All rights reserved  
 
 5 Labelling - Storage  
5.1 Means of delivery  
Calcium hypochlorite shall be delivered in plastic -coated steel drums, plastic pails or polyethylene bottles.  
In order that the purity of the product is not affected, the means of delivery shall not have been previously 
used for any different product or it shall have been specially cleaned and prepared before use.  
5.2 Labelling  
The following labelling requirements sh all apply to calcium hypochlorite  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
   
  
   Severe skin burns and eye damage  Signal word:  
Danger  
Hazard statement:  
May intensify fire; Oxidizer  
Harmful if swallowed  
Very toxic to aquatic life  
 
©RSB 2017 All rights reserved                  6 
 
 5.3 Transportation  
Nation 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 airtight containers in a cool, dry and well -ventilated room.  
5.4.2  Long term stability  
Heat stability: The stability of solid calcium hypochlorite depends on the water content.  
At temperatures above 177 °C, decompositio n is rapid with the evolution of oxygen and heat and thus 
increasing the risks of pressure build -up to blow off the lid or rupture the container.  
Decomposition also occurs at temperatures maintained above about 50 °C for longer periods.  
NOTE  1 Decomposit ion products are calcium chloride (CaCl 2), oxygen (O 2) and chlorine (Cl 2).  
NOTE 2  Chemical stability:  
Contamination can initiate a vigorous chemical reaction resulting in fire and/or explosion.  
5.4.3  Storage incompatibilities  
Keep away from acids, acidic salt s, ammonia and ammonium compounds, inflammable substances, organic 
compounds and moisture.  
5.5 Marking (for TC discussion if necessary to be included in this standard)  
The marking shall include the following information:  
̶ name: “aluminium sulfate” trade name a nd type;  
̶ net mass;  
̶ name and the address of the supplier and/or manufacturer;  
̶ statement of conformity to the standard.  
The conformity to the standards shall be validated by a national standard body after verifying the certificate of 
analysis accompanyin g the product.  DRS 353 -2: 2017  
7                 ©RSB2017  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  First aid  
A.2.1.1  In case of contact with the skin, rinse with copious amounts of water, remove contaminated 
clothing.  
A.2.1.1  In case of contact with the eyes or mucous membranes, rinse immediately with copious of 
amounts of water for at least 10 min and consult a doctor (danger of irreversible damage to the eye).  
A.2.1.1  In case of inhalation get to the fresh air and consult a doctor.  
A.2.1.1  If swallowed wash out the mouth with water and give water to drink. Do not induce vomiting 
(danger of perforation). Do not apply neutralization agents. Consult a doctor immediately.  
A.2.2  Spillage  
A.2.2.1  Wear respiratory and eye protection equipment and chemical resistant protecting gloves. Do not 
drain into waste water piping. Collect spilt solid product in separate plastic containers , do not accumulate.  
A.2.2.1  Contain spilt solution and absorb with inert absorbing material (kieselguhr, universal absorbent, 
etc. do not use sawdust). Solutions may be reduced with either sodium sulfite, sodium hydrogen sulfite, 
hydrogen peroxide or sod ium thiosulfate.  
A.2.2.1  Disposal shall be carried out in accordance with the local regulations. Clean contaminated tools 
by rinsing with plenty of water.  
A.2.3  Fire  
The material is not combustible, but due to the formation of oxygen as a decomposition by -product it will 
support combustion. Use air -independent respiratory equipment for firefighting . Use water to extinguish fire 
and to cool containers exposed to fire. D o not use dry chemical extinguishers containing ammonium 
compounds, e.g. monoammonium phosphate.  
  
©RSB 2017 All rights reserved                  8 
 
 Annex  B 
(informative)  
 
Determination of arsenic, antimony and selenium (atomic absorption 
spectrometry hydride technique)  
SAFETY PRECAUTIONS: Arsenic, antimony and s elenium and their hydrides are 
toxic. Handle with care.  
B.1 General principle  
Arsenious acid, antimonic acid and selenious acid, the As(III), Sb(III) and Se(IV) oxidation states of arsenic, 
antimony and selenium, respectively, are instantaneously converted by sodium borohydride reagent in acid 
solution to their volatile hydrides. The hydrides are purged continuously by argon or nitrogen into an 
appropriate atomizer of an atomic absorption spectrometer and converted to the gas -phase atoms. The 
sodium borohydride  reducing agent, by rapid generation of the elemental hydrides in an appropriate reaction 
cell, minimizes dilution of the hydrides by the carrier gas and provides rapid, sensitive determinations of 
arsenic, antimony and selenium.  
The sample is digested to  solubilize particulate As, Sb and Se. The digested solutions are treated separately 
for determination of As, Sb and Se to convert them to As(III), Sb(III) and Se(IV) oxidation states respectively.  
B.2 Interferences  
Interferences are minimized because the As,  Sb and Se hydrides are removed from the solution containing 
most potential interfering substances. Slight response variations occur when acid matrices are varied. Control 
these variations by treating standards and samples in the same manner. Low concentra tions of noble metals 
(approximately 100 μg/l of Ag, Au, Pt, Pd, etc.) concentrations of Cu, Ni and Pb at or greater than 1 mg/l, and 
concentrations between 0,1 mg/l and 1 mg/l of hydride -forming elements (Bi, Sn and Te) can suppress the 
response of As, Sb  and Se hydrides due to the formation of mixed metal – As-Sb or -Se compounds. The 
presence of As, Sb and Se in each other's matrices can cause similar suppression. Reduced nitrogen oxides 
resulting from HNO 3 digestion and nitrite also can suppress instrum ental response for all elements. Large 
concentrations of iodide interfere with the Se determination by reducing Se to its elemental form. Do not use 
any glassware for determining Se that has been used with iodide reduction of As(V).  
B.3 Reagents  
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 in 
accordance with ISO 3696 . 
B.3.1  Sodium tetrahydroborate (sodium borohydride).  
Dissolve 8 g NaBH4 in 200 ml of NaOH, c(NaOH) = 0,1 mol/l. Prepare fresh daily.  DRS 353 -2: 2017  
9                 ©RSB2017  All rights reserved  
 
 B.3.2  Sodium iodide,  pre-reductant solution .  
Dissolve 50 g Nal in 500 ml water. Prepare fresh daily.  
B.3.3  Sulfuric acid, solution c(H2SO4) = 9 mol/l.  
B.3.4  Sulfuric acid, solution c(H2SO4) = 1,25 mol/l.  
Cautiously add 35 ml sulfuric acid, density ( ρ) = 1,84 g/ml to about 400 ml water, allow to cool, and adjust 
volume to 500 ml.  
B.3.5  Nitric acid, density (ρ) = 1,42 g/ml.  
B.3.6  Perchloric acid, density (ρ) = 1,66 g/ml.  
B.3.7  Hydrochloric acid, density (ρ) = 1,16 g/ml.  
B.3.8  Argon (or nitrogen), commercial grade.  
B.3.9  Hydrogen, commercial grade.  
B.3.10  Arsenic (III) solut ions:  
̶ Stock As(III) solution: Dissolve 1,320 g arsenic trioxide, As2O3, in water containing 4 g of NaOH. Transfer 
quantitatively to 1 000 ml one -mark volumetric flask and make up to the mark with water and mix; 1,00 ml 
= 1,00 mg As(III);  
̶ Intermediate As(I II) solution: Dilute into 1 000 ml one -mark volumetric flask 10 ml stock As (III) solution to 
the mark with water containing 5 ml hydrochloric acid (C.3.7) and mix ; 1,00 ml = 10,0 µg As(III);  
̶ Standard As(III) solution: Dilute into 1 000 ml one -mark volume tric flask 10 ml intermediate As(III) solution 
to the mark with water containing the same concentration of acid used for sample preservation (2 ml to 5 
ml nitric acid (C.3.5)) and mix; 1,00 ml = 0,100 μg As(III). Prepare diluted solutions daily.  
B.3.11  Arsenic (V ) solutions:  
̶ Stock As(V) solution: Dissolve 1,534 g arsenic pentoxide, As2O5, in water containing 4 g NaOH. Transfer 
quantitatively to 1 000 ml one -mark volumetric flask and make up to the mark with water and mix; 1,00 ml 
= 1,00 mg As(V);  
̶ Intermediate As(V ) solution: Prepare as for As(III) above ; 1,00 ml = 10,0 µg As(V);  
̶ Standard As(V) solution: Prepare as for As(III) above; 1,00 ml = 0,100 µg As(V).  
  
©RSB 2017 All rights reserved                  10 
 
 B.3.12  Selenium (IV) solutions:  
 
̶ Stock Se(IV) solution: Dissolve 2,190 g sodium selenite, Na 2SeO 3 in water containing 10 ml hydrochloric 
acid (C.3.7) and transfer quantitatively to 1 000 ml one -mark volumetric flask and make up to the mark 
with water and mix; 1,00 ml = 1,00 mg Se(IV);  
̶ Intermediate Se(IV) solution: Dilute into 1 000 ml one -mark volume tric flask 10 ml stock Se (IV) solution to 
the mark with water containing 10 ml hydrochloric acid (C.3.7) and mix; 1,00 ml = 10,0 μg Se(IV);  
̶  Standard Se(IV) solution: Dilute into 1 000 ml one -mark volumetric flask 10 ml intermediate Se(IV) 
solution to the  mark with water containing the same concentration of acid used for sample preservation (2 
ml to 5 ml nitric acid (C.3.5)) and mix. Prepare solution daily when checking the equivalent of instrument 
response for Se(IV) and Se(VI); 1,00 ml = 0,100 μg Se(IV).  
B.3.13  Selenium (VI) solutions:  
̶ Stock Se(VI) solution: Dissolve 2,393 g sodium selenate Na2SeO4 in water containing 10 ml nitric acid 
(C.3.5). Transfer quantitatively to 1 000 ml one -mark volumetric flask and make up to the mark with water 
and mix; 1,00 ml = 1,0 0 mg Se(VI);  
̶ Intermediate Se(VI) solution: Prepare as for Se(IV) above ; 1,00 ml = 10,0 μg Se(VI);  
̶ Standard Se(VI) solution: Prepare as for Se(IV) above ; 1,00 ml = 0,100 μg Se(VI).  
B.3.14  Antimony solutions:  
̶ Stock Sb solution: Dry 2 g of potassium antimonyl tart rate hemihydrate (antimony potassium tartrate) 
(C4H4O7SbK.0,5 H2O) at 100 °C for 1h. Dissolve 1,669 g in water transfer quantitatively to 1 000 ml 
onemark volumetric flask and make up to the mark with water and mix; 1,00 ml = 1,00 mg Sb;  
̶ intermediate Sb s olution: Dilute into 1 000 ml one -mark volumetric flask 10 ml stock Sb solution to the 
mark with water containing 10 ml hydrochloric acid (C.3.7) and mix; 1,00 ml = 10,0 μg Sb;  
̶  standard Sb solution: Dilute into 1 000 ml one -mark volumetric flask 10 ml int ermediate Sb solution to the 
mark with water containing the same concentration of acid used for sample preservation (2 ml to 5 ml 
nitric acid (C.3.5)) and mix; 1,00 ml = 0,100 μg Sb. Prepare diluted solutions daily.  
B.4 Apparatus  
B.4.1  General  
Ordinary laboratory a pparatus and glassware, together with the following.  
B.4.2  Atomic absorption spectrometer  
Atomic absorption spectrometer, equipped with gas flow meters for argon (or nitrogen) and hydrogen, As, Sb 
and Se electrodeless discharge lamps with, background correction  at measurement wavelengths and 
appropriate strip -chart recorder.  DRS 353 -2: 2017  
11                 ©RSB2017  All rights reserved  
 
 NOTE  Certain atomic absorption atomizers and hydride reaction cells are available commercially for use with the 
sodium borohydride reagent.  
B.4.3  Atomizer  
Use one of the following:  
̶ Boling -type burner head for argon (or nitrogen) -air entrained -hydrogen flame;  
̶ Cylindrical quartz cell, 10 cm to 20 cm long, electrically heated by external Ni -Cr wire to 800 °C to 900 °C;  
̶ Cylindrical quartz cell with internal fuel rich hydrogen -oxygen (air) flame.  
The transparency of quartz cells deteriorates over several months of use. The transparency can be restored 
by treatment with 40 % hydrofluoric acid (HF).  
SAFETY PRECAUTIONS: Be careful in handling HF which is toxic and corrosive and 
avoid prolonged contact of quartz with HF.  
B.4.4  Reaction cell for producing As, Sb or Se hydrides An example of reaction cell is given in 
Figure B.1.  
NOTE  A commercially available system is acceptable if it utilizes liquid sodium borohydride reagents; accepts 
samples digeste d in accordance with C.5.3, accepts between 4 mol/l to 6 mol/l (HCl); and is efficiently and precisely stirred 
by the purging gas and/or a magnetic stirrer.  
Irrespective of the hydride reaction cell -atomizer system selected, it shall meet the following qu ality-control 
considerations:  
a) it shall provide a precise and reproducible calibration curve between 0 μg/l and 20μg/l As, Sb or Se and a 
detection limit between 0,1 μg/l and 0,5μg/l As, Sb or Se;  
b) when carried through the entire procedure, oxidation state couples (As(III) - As(V) or Se(IV) - Se(VI)) shall 
cause equal instrument response; and  
c) Sample digestion shall yield 90 % or greater recovery of added As(III), As(V), Se(VI), Se(IV) or Sb.  
B.4.5  Dropper and syringe, capable of delivering 0,5 ml to 3,0 ml sodiu m borohydride reagent.  
Exact and reproducible addition is required so that production of hydrogen gas does not vary significantly 
between determinations.   
©RSB 2017 All rights reserved                  12 
 
  
Key  
1. beaker 250ml  6  gas dispersion tube  
2. rubber stopper  7  burner  
3. dropper  8  hydrogen  
4. auxilia ry nitrogen  9  nitrogen outlet tube  
Figure B.1 — Reaction cell for producing As, Sb or Se hydrides  
B.5 Procedure  
B.5.1  Preparation of the apparatus  
B.5.1.1  Connect the inlet of the reaction cell with the auxiliary purging gas controlled by a flow meter. If a 
dryin g cell between the reaction cell and the atomizer is necessary, use only anhydrous CaCl 2 and not CaSO 4, 
because it can retain SeH 2. Before using the hydride generation/analysis system, optimize operating 
parameters.  
B.5.1.2  Aspirate aqueous solutions of A s, Sb and Se directly into the flame to facilitate atomizer 
alignment. Align quartz atomizers for maximum absorbance. Establish a purging gas flow, concentration and 
rate of addition of sodium borohydride reagent, solution volume, and stirring rate for opt imum instrument 
response for the chemical species to be analysed. If a quartz atomizer is used, optimize cell temperature. If 
sodium borohydride reagent is added too quickly, rapid evolution of hydrogen will unbalance the system. If the 
volume of solution being purged is too large, the absorption signal will be decreased. Recommended 
wavelengths are 193,7 nm, 196,0 nm and 217,6 nm for As, Se and Sb, respectively.  
B.5.2  Preparation of calibration solutions  
Transfer 0,00 ml; 1,00 ml; 2,00 ml; 5,00 ml; 10,00 ml; 15,00 ml and 20,00 ml of standard solutions of As(III), 
Se(IV) or Sb to 100 ml volumetric flasks and make up to volume with water containing the same acid 
DRS 353 -2: 2017  
13                 ©RSB2017  All rights reserved  
 
 concentration used for sample preservation (co mmonly 2 ml to 5 ml nitric acid (C.3.5)).This yields calibrations 
solutions of 0 μg/l, 1 μg/l, 2 μg/l, 5 μg/l, 10 μg/l, 15 µg/l and 20 μg/l As, Se or Sb. Prepare fresh daily.  
B.5.3  Preparation of test solutions and standard solutions  
B.5.3.1  Add 50 ml of the s ample or As(III), Se(VI) or Sb standard solution to 250 ml beaker. Alternatively, 
prepare standard solutions by adding aliquots of solutions containing 5 μg As, Se or Sb directly to the beaker 
and dilute to 50 ml in this beaker, thus achieving a concentrat ion of 100 µg/l of the respective solutions. Add 7 
ml sulfuric acid c(H2SO 4) = 9 mol/l (C.3.3) and 5 ml nitric acid (C.3.5). Add a small boiling chip or glass beads 
if necessary. Evaporate to SO 3 fumes. Maintain oxidizing conditions at all times by adding small amounts of 
nitric acid, to prevent solution from darkening.  
B.5.3.2  Maintain an excess of nitric acid until all organic matter is destroyed. Complete digestion is 
usually indicated by a li ght-coloured solution. Cool slightly, add 25 ml of water and 1 ml of perchloric acid 
(C.3.6) and again evaporate to SO 3 fumes to expel oxides of nitrogen.  
B.5.3.3  Monitor the effectiveness of the digestion procedure used by adding 5 ml of a standard arsen ic 
solution, 5 ml of a standard selenium solution or 5 ml of a standard antimony solution to 50 ml of the sample 
and measuring recovery. Average recoveries shall be greater than 90 %. Alternatively, use 100 ml micro -
Kjeldahl flasks for the digestion of tot al recoverable arsenic, selenium or antimony, thereby improving 
digestion effectiveness. After the final evaporation of the SO 3 fumes, dilute to 50 ml for arsenic measurements 
or 30 ml for selenium and antimony measurements.  
B.5.4  Determination of arsenic with sodium borohydride  
To 50 ml of the digested standard solution or test solution in a 250 ml beaker (see Figure C.1) add 5 ml 
hydrochloric acid (C.3.7) and mix. Add 5 ml sodium iodide pre -reductant solution (C.3.2), mix and wait at least 
30 min.  
NOTE  The sodium iodide has not been found necessary for certain hydride reaction cell designs if a 20 % to 30 % 
loss in instrument sensitivity is not important and variables of solution acid conditions, temperatures, and volumes for 
production of As(V) and arsine c an be strictly controlled. This might require an automated delivery system.  
Attach one beaker the first time to the rubber stopper containing the gas dispersion tube for the purging gas, 
the sodium borohydride reagent inlet, and the outlet to the atomizer . Turn on strip -chart recorder and wait until 
the base line is established by the purging gas and all air is expelled from the reaction cell. Add 0,5 ml sodium 
borohydride reagent (C.3.1). After the instrument absorbance has reached a maximum and returned to the 
base line, remove the beaker, rinse the dispersion tube with water, and proceed to the next test solution or 
standard solution. Periodically compare standard As(III) and As(V) curves for response consistency. Check for 
the presence of chemical inter ferences that suppress instrument response for arsine by treating a digested 
sample with 10 μg/l As(III) or As(V) as appropriate. Average recoveries shall be not less than 90 %.  
B.5.5  Determination of selenium with sodium borohydride  
To 30 ml of the digested s tandard solution or test solution, or to 30 ml of the undigested standard, or the 
sample in a 250 ml beaker, add 15 ml hydrochloric acid (C.3.7) and mix. Heat for a pre -determined period at a 
temperature between  90 °C to 100 °C. Alternatively autoclave at  121 °C in capped containers for 60 min, or 
heat for a predetermined time in open test tubes using a 90 °C to 100 °C hot water bath or an aluminium block 
digester. Check the effectiveness of the selected heating by demonstrating equal instrument responses for 
calibration curves prepared either from standard Se(IV) or from Se(VI) solutions. Effective heat exposure for 
converting Se(VI) to Se(IV), with no loss of Se(IV), ranges between 5 min to 60 min when open beakers or 
test tubes are used. Do not digest st andard Se(IV) and Se(Vl) solutions used for this check of equivalency. 
After pre -reduction of Se(VI) and Se(IV) attach beakers, one at a time, to the purge apparatus. For each, turn  
©RSB 2017 All rights reserved                  14 
 
 on the strip -chart recorder and wait until the base line is established. A dd 0,50 ml sodium borohydride reagent 
(C.3.1). After the instrument absorbance has reached a maximum and returned to the base line, remove the 
beaker, rinse the dispersion tube with water and proceed to the next test solution or standard solution. Check 
for the presence of chemical interferences that suppress the selenium hydride instrument response by treating 
a digested sample with 10 μg/l Se(IV). Average recoveries shall be not less than 90 %.  
B.5.6  Determination of antimony with sodium borohydride  
To 30 ml o f the digested standard solution or the test solution, or to 30 ml of the undigested standard solution, 
or to the test solution in a 250 ml beaker, add 15 ml hydrochloric acid (C.3.7) and mix. Heat for a 
predetermined period (between 5 min and 60 min) betw een 90 °C to 100 °C. After the pre -reduction of Sb, 
attach beakers, one at a time, to the purge apparatus. For each, turn on the strip -chart recorder and wait until 
the base line is established. Add 0,50 ml sodium borohydride reagent (C.3.1). After the ins trument absorbance 
has reached a maximum and has returned to the base line, remove beaker, rinse the dispersion tube with 
water and proceed to the next test solution or standard solution. Check for the presence of chemical 
interferences that suppress the a ntimony hydride instrument response by treating a digested sample with 10 
μg/l Sb. Average recoveries shall be not less than 90 %.  
B.6 Calculation  
Determine the calibration curve by plotting the peak heights of standard solutions versus concentration. 
Measure  the peak heights of samples and read concentrations from the calibration curve. If sample was 
diluted (or concentrated) before sample digestion, apply an appropriate factor.  
B.7 Repeatability limit  
The absolute difference between two single test results, obt ained under repeatability conditions, shall not be 
greater than the repeatability value, r, as calculated from the following formula:  
r = 0,001 z  (C.1)  
where z is the mean of the two results, expressed in mass fraction in percent (%).  
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.  DRS 353 -2: 2017  
15                 ©RSB2017  All rights reserved  
 
 Annex  C 
(informative)  
 
General information on calcium hypochlorite  
C.1 Origin  
C.1.1  Raw materials  
Calcium hypochlorite is manufactured from chlorine, calcium hydroxide and sodium hydroxide.  
C.1.2  Manufacturing process  
It is produced by drying a filter cake of neutral calcium hypochlorite di hydrate that is usually prepared from 
calcium hydroxide (hydrated lime) (Ca(OH) 2), sodium hydroxide (caustic soda) (NaOH), and chlorine (Cl 2).  
C.2 Use 
C.2.1  Function  
Its functions in water treatment are the removal of ammonium compounds, the oxidation of sulfides,  the 
oxidation of iron (II) to iron (III) and as a disinfectant.  
A.2.1.  Form in which it is used  
It is used in aqueous solutions, usually as a mass fraction of 1 % to 4 %.  
C.2.2  Treatment dose  
The treatment dose depends on the composition of the raw water. Care should be taken not to exceed a 
maximum concentration of available chlorine in the water supply, usually a few tenths of 1 mg/l .  
C.2.3  Means of application  
It is applied using a metering pump, from a dissolving tank.  
C.2.4  Secondary effects  
The secondary effects i nclude the following:  
̶ Slight increase in pH;   
©RSB 2017 All rights reserved                  16 
 
 ̶ Slight increase in the chloride content;  
̶ Odour and colour removal;  
̶ Oxidation of organic compounds;  
̶ Formation of halogenated organic substances, especially trihalomethanes, is possible;  
̶ Local precipitation of carbonate at injection point.  
C.2.5  Removal of excess product  
Excess active chlorine can be removed by utilising a reducing agent such as sulfur dioxide gas or an aqueous 
solution of a sulfite compound.  
Passing through activated carbon is also effective.  
  DRS 353 -2: 2017  
17                 ©RSB2017  All rights reserved  
 
 Annex  D 
(informative)  
 
Recommended test methods  
D.1 Test methods  
D.1.1  Sampling  
Observe the general recommendations of ISO 3165 and take into account ISO 6206.  Prepare the laboratory 
sample(s) required by the relevant procedure described in ISO 8213.  
 
D.1.2  Analysis  
D.1.2.1  Determination of calcium hypochlorite content (main product)  
D.1.2.1.1  Principle  
Calcium 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.  
NOTE 1:  It detects all oxidizing agents being active in a weak acidic solution, i.e. hypochlorite/chlorine, iodate, and 
partially chloramines, Fe(III), etc. Not covered under these conditions are bromate and chlorate.  
NOTE 2:  The titration may also be carried out potentiometrically, with automatic titration, in which case the addition of 
soluble starch is unnecessary.  
D.1.2.1.2  Reagents  
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 as specified 
in ISO 3696.  
D.1.2.1.2.1  Potassium iodide crystals (KI).  
D.1.2.1.2.2  Glacial acetic acid.  
D.1.2.1.2.3  Hydrochloric acid solution.  
D.1.2.1.2.4  Concentrated hydrochloric acid density ρ (HCl) = 1,16 g/ml diluted 1 + 1 by volume with 
water.  
D.1.2.1.2.5  Sodium thiosulfate standard volumetric solution, c(Na 2S2O3.5H 2O) = 0,1 mol/l.   
©RSB 2017 All rights reserved                  18 
 
 Standard volumetric solutions are commercially available, which might have to be diluted.  
Alternatively a standard volumetric solution may be prepared by the following procedure: Dissolve 24,8 g 
Na2S2O3.5H 2O in a 1 000 ml one -mark volumetric flask in abou t 0,75 l water. After the temperature has 
equalized 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 3) = 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 ( D.1.2.1.2.3) and (5 ± 1) ml of starch solution 
(D.1.2.1.2.5). Titrate immediately with the potassium iodate standard reference solution until the appearance 
of a blue  coloration persisting for at least 30 s. Record the volume (V) of iodate used.  
The concentration, c, of the sodium thiosulfate standard volumetric solution (Na 2S2O3.5H 2O), expressed in 
moles per litre is given by the following formula:  
C=𝑚
𝑉×49,0317 
where  
 m  is the mass, in milligrams, of potassium iodate (KIO 3) weighed;  
 V  is the volume, in millilitres, of the sodium thiosulfate standard volumetric solution used.  
D.1.2.1.2. 6 Starch solution, mass fraction 1 %.  
Make a slurry with (1 ± 0,1) g starch and (5 ± 1) ml water. Add (90 ± 5) ml boiling water to the slurry. Stir to 
dissolve it and cool the solution. This solution needs refrigeration to avoid the decomposition of the starch 
which results in a vague end poin t. Keep the solution cool and use it within one week.  
Commercial indicators for iodine titration exist and may be used in place of the described starch solution 
provided that their efficiency has been previously tested.  
D.1.2.1.3  Apparatus  
Ordinary laboratory appa ratus and glassware, together with the following:  
D.1.2.1.3.1  Laboratory sonic vibrator.  
 
D.1.2.1.4  Procedure  
D.1.2.1.4.1  Test portion  
Weigh, to the nearest 0,1 mg, 3,5 g of the laboratory sample ( m1) into a tarred stoppered weighing bottle.  DRS 353 -2: 2017  
19                 ©RSB2017  All rights reserved  
 
 D.1.2.1.4.2  Determination  
D.1.2.1.4.2.1  Transfer the test portion to a 500 ml volumetric flask with 300 ml of water, stopper, and place 
in the sonic vibrator for 10 min, swirling it occasionally until the test portion is in a solution. Make up to the 
mark with water.  
D.1.2.1.4.2.2  Place a magn etic stirring bar into the volumetric flask and begin mixing. Transfer 25 ml, while 
the test portion is being stirred and without allowing any insoluble matter to settle out, into the 500 ml conical 
flask.  
D.1.2.1.4.2.3  Add 100 ml of water and 2 g of pot assium iodide ( D.1.2.1.2.1), and mix to dissolve. Add 8 ml 
of glacial acetic acid ( D.1.2.1.2.2), stir and titrate immediately with the sodium thiosulfate standard volumetric 
solution ( D.1.2.1.2.4) to a light yellow colour. Add 3 ml of the starch solution ( D.1.2.1.2.5) and continue 
titration to the disappearance of the blue black colour. Record the volume V1, of the sodium thiosulfate 
standard volumetric solution used.  
D.1.2.1.5  Expression of results  
The chlorine (Cl 2) content, w1, expressed as a mass fraction in %, i s given by the following formula:  
𝒘𝟏=𝑽𝟏×𝐜×𝟑𝟓.𝟒𝟓𝟑×𝟏𝟎𝟎
𝒎𝟏                                  (2) 
V1: is the volume, in millilitres, of the sodium thiosulfate solution ( D.1.2.1.2.4) used for the titration;  
c: is the concentration, in moles per litre, of the sodium thiosulfate standard volumetric solution ( D.1.2.1.2.4);  
m1: is the mass, in milligrams, of the test portion ( D.1.2.1.4.1);  
35.453 : is the mass in milligrams of chlorine (Cl2) corresponding to 1,00 ml of sodium thiosulfate solution 
c(Na 2S2O3.5H2O) = 1,000 mol/l.  
The Ca(ClO) 2 content, w2, expressed as a mass fraction of product, is given by the following formula:  
𝒘𝟐=𝒘𝟏×𝟑.𝟓𝟕𝟒𝟔
𝟑.𝟓𝟒𝟓𝟑        (3) 
D.1.2.1.6  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 = 0,01 × z (4) 
Where z is the mean of the two results, expr essed in mass fraction in percent (%)  
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 wi thin short 
intervals of time.   
©RSB 2017 All rights reserved                  20 
 
 D.1.2.2   Dissolution quality (available chlorine after 1 min)  
D.1.2.2.1  Principle  
A representative sample is stirred in water for 1 min and immediately titrated iodometrically. Dissolved calcium 
hypochlorite reacts with iodide in the presence  of acetic acidic to release iodine, which is titrated with sodium 
thiosulfate standard volumetric solution.  
NOTE  The titration may be carried out manually with the addition of starch solution as a visual indicator, or 
potentiometrically with automatic ti tration and without an indicator.  
D.1.2.2.2  Reagents  
All reagents shall be of a recognized analytical grade and the water used shall conform to grade 3 as specified 
in ISO 3696.  
D.1.2.2.2.1  Sodium thiosulfate standard volumetric solution, c(Na2S2O3.5H2O) = 0,1 mol/l (see 
D.1.2.1.2.4).  
D.1.2.2.2.2  Potassium iodide, virtually free of iodate.  
D.1.2.2.2.3  Glacial acetic acid  
D.1.2.2.2.4  Starch indicator solution, mass fraction 1 % (see D.1.2.1.2.5)  
D.1.2.2.3  Apparatus  
Ordinary laboratory apparatus and glassware  
D.1.2.2.4  Procedure  
From a representative sample of the product weigh 1,5 g to the nearest 1 mg (m 2). Add the test portion to a 
beaker containing 1 000 ml of water (at a temperature of 20 °C to 25 °C)  and by use of a magnetic stirrer 
agitate the contents.  
After 1 min stop the stirrer and remove a 25 ml aliquot by use of a pipette. Transfer to a conical flask 
containing 100 ml of water, add 2 g of potassium iodide crystals ( D.1.2.2.2.2), 8 ml of acetic  acid ( D.1.2.2.2.3) 
and titrate the liberated iodine with sodium thiosulfate standard volumetric solution ( D.1.2.2.2.1) to a light 
yellow colour. Add 3 ml of the starch indicator solution ( D.1.2.2.2.4) and continue titration to the 
disappearance of the blue-black colour. Record the volume (V 2) of the sodium thiosulfate standard volumetric 
solution used.  
D.1.2.2.5  Expression of results  
The available chlorine which is released within 1 min, ( w3), expressed as a mass fraction in % of product is 
given by the followi ng formula:  DRS 353 -2: 2017  
21                 ©RSB2017  All rights reserved  
 
 𝒘𝟑=𝒗𝟐×𝐜×𝟑𝟓.𝟒𝟓𝟑×𝟒𝟎×𝟏𝟎𝟎
𝒎𝟐    (5) 
Where  
c: is the concentration in moles per litre of sodium thiosulfate standard volumetric solution ( D.1.2.2.2.1);  
V2 : is the volume, in millilitres, of the sodium thiosulfate standard volumetric solution  
(D.1.2.2.2.1);  
m2: is the mass, in milligrams, of the test portion;  
35,453: is the mass in milligrams of chlorine (Cl 2) corresponding to 1,00 ml of sodium thiosulfate st andard 
volumetric solution c(Na 2S2O3.5H 2O) = 1,000 mol/l.  
D.1.2.2.6  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 fo llowing formula:  
r = 0,01 z  (6) 
Where z  is the mean of the two results, expressed in mass fraction in percent (%)  
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.  
D.1.2.3  Impurities  
D.1.2.3.1  Insoluble matter  
D.1.2.3.1.1  Principle  
A representative sample of calcium hypochlorite is dissolved into water. The insoluble matter is separated  by 
filtration then dried and weighed.  
D.1.2.3.1.2  Apparatus  
Ordinary laboratory apparatus and glassware together with the following:  
D.1.2.3.1.2.1  Sintered glass crucible of porosity P40 (pores size between 16 μm to 40 μm).  
D.1.2.3.1.2.2  Oven capable of being cont rolled at (105 ± 3) °C   
©RSB 2017 All rights reserved                  22 
 
 D.1.2.3.1.3  Procedure  
Weigh approximately 10 g of the representative sample (m3) to the nearest 0,01 g and dissolve in 1 000 ml of 
water by stirring for 30 min. Then filter the solution under vacuum through a dried and weighed glass filter 
(D.1.2.3.1.2.1). After the filtration, wash the residue with 20 ml of water and remove excess water by filtering 
under vacuum. Dry the residue at (105 ± 3) °C in the oven ( D.1.2.3.1.2.2) until the mass remains constant and 
weigh it (m4) after cooling in a desi ccator.  
D.1.2.3.1.4  Expression of results  
The insoluble matter expressed as a mass fraction in %, w4 in the product is given by the following formula:  
𝒘𝟒=𝒎𝟒
𝒎𝟑×𝟏𝟎𝟎  (7) 
Where  
m4 is the mass, in grams, of the residue;  
m3 is the mass, in grams, of the test portion.  
D.1.2.3.2  Water content  
WARNING If the product is overheated (see 6.5.2), a violent decomposition or explosion can occur. This test shall 
only be carried out by experienced laboratory staff (usually by the manufacturing company) and not by the end 
users.  
The determination of the water content of calcium hypochlorite may be achieved by drying a sample at 
temperature between 105 °C and 110 °C until the mass of dried residue remains constant.  
D.1.2.4  Chemical parameters  
D.1.2.4.1  General  
Determination of antimony (Sb), arse nic (As), cadmium (Cd), chromium (Cr), lead (Pb), nickel (Ni) and 
selenium (Se).  
D.1.2.4.2  Principle  
The elements arsenic, antimony, cadmium, chromium, lead, nickel and selenium are determined by atomic 
absorption spectrometry.  
D.1.2.4.3  Reagents  
All reagents shall be of a recognized analytical grade and the water used shall conform to the grade 2 
specified in ISO 3696.  DRS 353 -2: 2017  
23                 ©RSB2017  All rights reserved  
 
 D.1.2.4.3.1  Nitric acid, concentrated, density ρ = 1,42 g/ml.  
D.1.2.4.4  Procedure  
D.1.2.4.4.1  Test portion  
Weigh, to the nearest 0,001 g, 10 g ( m5) of the laboratory sample into a 100 ml one -mark volumetric flask.  
D.1.2.4.4.2  Test solution  
Add 1 ml of nitric acid ( D.1.2.4.3.1) to the test portion; dilute with a few millilitres of water and mix. Make up to 
volume with water and homogenize.  
D.1.2.4.4.3  Determination  
Determi ne the content of elements in the test solution ( D.1.2.4.4.2) 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 converted to 
give the final concentration according to the formula in D.1.2.4.4.4.  
D.1.2.4.4.4  Expression of results  
From the interim result ( y) determined (see D.1.2.4.4.3), the content, w5, of each element in the laboratory 
sample, expressed in milligrams per kilogram of available chlorine is given by the following formula:  
𝒘𝟓=𝒚×𝑽
𝒎𝟓×𝟏𝟎𝟎
𝒘𝟏 (8) 
Where  
y: is the interim result ( D.1.2.4.4.3);  
V:  is the volume,  expressed in millilitres, of the test solutions ( D.1.2.4.4.2) (= 100 ml);  
m5:  is the mass, expressed in grams, of the test portion ( D.1.2.4.4.1);  
w1: is the available chlorine content in mass fraction of product ( D.1.2.1.5).  
  
©RSB 2017 All rights reserved                  24 
 
 D.1.2.4.5  Determination of the mercury content (Hg)  
D.1.2.4.5.1  Principle  
The element mercury is determined by flameless atomic absorption spectrometry in accordance with ISO 
12846:2012, Clause 7 .  
D.1.2.4.5.2  Reagents  
All reagents shall be of a recognized analytical grade and the water  used shall conform to the grade 3 
specified in EN ISO 3696.  
D.1.2.4.5.2.1  Potassium permanganate solution, c(KMnO 4) = 50 g/l.  
D.1.2.4.5.2.2  Sulfuric acid, concentrated, density ρ = 1,84 g/ml.  
D.1.2.4.5.2.3  Hydroxylammonium chloride solution, c(NH 2OH.HCl) = 100 g/l.  
D.1.2.4.5.2.4  Potassium dichromate solution, c(K2Cr2O7) = 4 g/l in 50 % ( V/V) nitric acid solution.  
D.1.2.4.5.3  Procedure  
D.1.2.4.5.3.A  Test portion  
Weigh, to the nearest 0,01 g, 10 g ( m6) of the laboratory sample, into a glass beaker.  
D.1.2.4.5.3.B  Test solution  
D.1.2.4.5.3.B.1 Quantitatively transfer the test portion to a washing flask (e.g. Durand bottle), capacity 250 
ml, and 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. Transfe r to a volumetric flask (solution A).  
D.1.2.4.5.3. B.2 Accurately pipette 10 ml of the solution A. Transfer to a 250 ml conical flask and add 60 ml of 
water, 20 ml of a potassium permanganate solution ( D.1.2.4.5.2.1) and five 1 ml portions of sulfuric acid  
(D.1.2.4.5.2.2). Heat and keep boiling for 10 min. Allow to cool. Dissolve the precipitate (MnO 2) with 
hydroxylammonium chloride ( D.1.2.4.5.2.3), add 5 ml of the potassium dichromate solution ( D.1.2.4.5.2.4) and 
transfer to a 100 ml volumetric flask. Make  up to the mark with water and mix.  
D.1.2.4.5.3.C  Determination  
Proceed as described in ISO 12846:2012 , Clause 7  
D.1.2.4.5.4  Expression of result  
The interim result for mercury content ( y) expressed in milligrams is given by the following formula:  DRS 353 -2: 2017  
25                 ©RSB2017  All rights reserved  
 
 y = yA×V10T  (9) 
 
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, C1, in milligrams per kilogram of available chlorine is given by t he following formula:  
 
𝑪𝟏=𝒚×𝟏𝟎
𝒎𝟔×𝟏𝟎𝟎
𝒘𝟏 (10) 
Where  
m6: is the mass, expressed in grams, of the test portion;  
w1: is the available chlorine content in mass fraction ( D.1.2.1.5).   
©RSB 2017 All rights reserved                  26 
 
 Annex  E 
(informative)  
 
Environmental, health and safety precautions within  chemical laboratory  
When preparing the analytical methods for the application of this document, consideration was given to 
minimize any environmental impacts caused by the methods of analysis.  
It is the users’ responsibility to use safe and proper techni ques when handling materials during the methods of 
analysis specified in this document.  
The following list is not exhaustive, however users of the analytical methods referred in this document may 
use it as a guide for the use of safe and proper techniques . They should:  
̶ Investigate if legislation and national laws, regulations and administrative provisions apply;  
̶  
̶ Consult manufacturers / suppliers for specific details such as material safety data sheets and other 
recommendations;  
̶ Use safety 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 toxic and/ or human c arcinogens 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 satisfactor y manner: including 
chemicals for laboratory test, test specimens, unused solvents and reagents that have to be disposed of.  DRS 353 -2: 2017  
27                 ©RSB2017  All rights reserved  
 
 Bibliography  
[1] ISO 3696, Water for analytical laboratory use - Specification and test methods  
[2]  ISO 12846:2012, Water quality - Deter mination of mercury - Method using atomic absorption 
spectrometry (AAS) with and without enrichment  
[3] ISO 8213, Chemical products for industrial use — Sampling techniques — Solid chemical products in 
the form of particles varying from powders to coarse lumps  
[4] ISO 8288, Water quality — Determination of cobalt, nickel, copper, zinc, cadmium and lead — Flame 
atomic absorption spectrometric methods  
[5] ISO 9174, Water quality — Determination of chromium — Atomic absorption spectrometric methods  
  DRS 353-2: 2017  
ICS 71.100. 80 
 
 
©RSB 2017 All  rights reserved