FINAL DRAFT UGANDA 
STANDARD  
  FDUS 925
First Edition
2012-mm-dd
 
 
 Reference numbe r
FDUS 925: 2012
© UNBS 2012 
  
Chemicals used for treatment of water intended for human 
consumption — Sodium hypochlorite — Specification 
 FDUS 925: 2012 
ii © UNBS 2010 – All rights reserved
 Compliance with this standard does not, of itself confer immunity from legal obligations 
A Uganda Standard does not purport to include all necessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2012  
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilised in any 
form or by any means, electronic or mechanical, in cluding photocopying and microfilm, without prior written 
permission from UNBS. 
Requests for permission to reproduce this document should be addressed to 
The Executive Director 
Uganda National Bureau of Standards 
P.O. Box 6329 
Kampala  
Uganda 
Tel: 256 414 505 995 
Fax: 256 414 286 123 
E-mail: info@unbs.go.ug  
Web: www.unbs.go.ug  
 FDUS 925:2012 
© UNBS 2012 – All rights reserved  iii
 Foreword 
Uganda National Bureau of Standards (UNBS) is a parastatal under the Ministry  of Tourism, Trade and 
Industry established under Cap 327, of the Laws of Uganda.  UNBS is mandated to co-ordinate the 
elaboration of standards and is  
(a) a member of International Organisation for Standardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex A limentarius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT/SPS Agr eements of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried out through Technical Committees. A Technical 
Committee is established to deliberate on standards in a gi ven field or area and consists of representatives of 
consumers, traders, academician s, manufacturers, governme nt and other stakeholders. 
Draft Uganda Standards adopted by the Technical Committ ee are widely circulated to stakeholders and the 
general public for comments. The committee reviews the comments before recommending the draft standards 
for approval and declaration as Uganda Standards by the National Standards Council.  
Committee membership 
The following organizations were represented on the Chemicals and environment standards Technical 
Committee (UNBS/TC 5), during the development of this standard: 
• Britania Allied Industries Ltd 
• Davis and Shirtliff 
• Desbro (U) Ltd 
• Government Analytical Laboratories 
• Kyambogo University - Chemistry Department 
• Makerere University - College of Ag riculture and Environmental Sciences 
• National Water and Sewe rage Corporation (NWSC) 
• National Environment Management Authority (NEMA) 
• Uganda Industrial Research Institute (UIRI) 
• Uganda National Bureau of Standards (UNBS) 
 
 FINAL DRAFT UGANDA STANDARD FDUS 925: 2012
 
© UNBS 2012 – All rights reserved  1
 Chemicals used for treatment of water intended for human 
consumption — Sodium hypochlorite — Specification 
1 Scope 
This Final Draft Uganda Standard specifies the require ments and methods of sampling and test for sodium 
hypochlorite solution used for disinfection 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 referenced 
document (including any amendments) applies. 
ISO 3696,  Water for analytical laboratory use — Specifications and test methods 
ISO 3165,  Sampling of chemical products for industrial use — Safety in sampling 
ISO 6206, Chemical products for industrial use — Sampling — Vocabulary 
3 Description 
Sodium hypochlorite is a chemical compound with a relative molecular mass of 74.44 and it is commonly 
known as liquid bleach, soda bleach or sodium oxychloride. 
4 Requirements  
4.1 General   
4.1.1.  The sodium hypochlorite solution shall be a clear or slightly cloudy liquid and shall be miscible in 
all proportions with water. 4.1.2  The sodium hypochlorite solution supplied shall contain no soluble mineral or organic substances 
in a quantity that would be deleterious or injurious to anyone consuming water disinfected with acceptable 
quantities of the hypochlorite. 
4.2 Physical and chemical requirements 
Sodium hypochlorite shall conform to the limits specifi ed for the physical and chemical characteristics laid 
out in Table 1. FDUS 925: 2012 
2 © UNBS 2012 – All rights reserved
 Table 1 — Physical and chemical requirements  
Parameter Requirement  Method of test 
Odour faint chlorinous odour - 
Density 1.0 g/mL - 1.14 g/mL at 20 °C. - 
Available chlorine 
content 10.0 g/L to 15.0 g/L avai lable chlorine at the 
time of delivery (1.0 % to 1.5 % weight/volume) Annex A 
Total free alkali (as NaOH) Shall not exceed 1.2% weight by volume. Annex B 
Insoluble matter  Not more than 0.15% by weight of insoluble matter Annex C 
pH 9 to 12 - 
 
5 Sampling 
5.1 General 
The sampling procedure in Table 2 shall be applied in determining whether a lot, submitted for inspection 
and test, complies with the relevant requirements of this specification. 
Table 2 — Number of containers to be taken for sampling various lot sizes 
Lot size number of containers Sample size number of containers 
1 to 4 All 
5 to 50 4 
51 to 100 5 
101 to 500 8 
501 to 1500 10 
1501 and above 12 
 
5.2 Sampling from tankers 
Take from four levels in the tanker  or at four stages during filling of the tanker, a composite sample of 500 
mL. Divide this sample into two equal portions and place each portion in a sample bottle. Use one portion 
for the determination of the insoluble matter, the available chlorine and the free sodium hydroxide 
contents. 
5.3 Sampling from other containers 
5.3.1 Containers with the capacity more than one litre 
From the lot, take at random the number of containers relative to the lot size as given in Table 2. From 
each container so drawn take a 500 mL sample. Divi de each sample into two equal portions and place 
each portion in a sample bottle. Use one portion of  each sample for the determination of the available 
chlorine and the free sodium hydroxide contents and reserve the other portion for the determination of the 
sodium chlorate content. FDUS 925: 2012 
© UNBS 2012 – All rights reserved  3
 The containers and the samples so taken shall be deemed to represent the lot.  
5.3.2 Containers with the capacity of or less one litre 
From the lot, take at random the number of containers relative to the lot size as given in Table 2. If the 
containers are packed in cartons, take  at random the number of cartons relative to the lot size and from 
each carton so drawn take at random one container. Use half of the samples for the determination of the 
insoluble matter, available chlorine a nd the free sodium hydroxide contents. 
The containers and the samples so taken shall be deemed to represent the lot.  
5.4 Compliance with the specification  
The lot shall be deemed to comply with requirements of the specification, if after sampling of the 
containers and testing of the samples taken in  accordance with 5.3, no defective is found. 
6 Packaging, labeling and storage 
6.1 Packaging  
Sodium hypochlorite shall be packed in 
a) containers of polyethylene or polyvinyl chloride (PVC) with external glass fibre reinforcement 
(GFR), and   
b) steel tank wagons lined with rubber or coated with suitable plastic. 
The containers shall be filled in such a manner that  no pressure can build up inside and no liquid can 
escape. The closure shall be protected from unintentional opening. 
6.2 Marking and labelling  
The following information shall be legibly and indelibly marked on the container: 
a) name of product, 'SODIUM HYPOCHLORITE'; 
b) chemical formular (NaCIO or NaOCI); c) name and address of manufacturer or supplier or both;  
d) net volume of the contents; 
e) batch number or mark/code in lieu of the number;  
f) nominal available chlorine content; 
g) shelf life; 
h) instructions for use;  i) storage instructions with the words, 'STORE IN A COOL PLACE' and “KEEP AWAY FROM 
DIRECT SUNLIGHT”;  
j) safety instructions with the words: 
(i) “KEEP AWAY FROM CHILDREN”; FDUS 925: 2012 
4 © UNBS 2012 – All rights reserved
 (ii) “HARMFUL IF SWALLOWED OR INHALED”; 
(iii) “AVOID CONTACT WITH EYES, SKIN AND CLOTHING”; 
(iv) “AVOID BREATHING MIST AND ALWAYS KEEP CONTAINER CLOSED AFTER USE”; and 
(v) “WASH HANDS AFTER USE”; and 
k) first aid instructions, “IF SWALLOWED DO  NOT INDUCE VOMITING. GIVE LARGE QUANTITIES 
OF WATER AND SEEK FOR MEDICAL ADVISE”. 
6.3 Bulk storage 
Sodium hypochlorite shall be protected against light and pa rticularly direct sunlight. It shall be stored in 
cool rooms in containers made from metal with internal  coating or suitable plastic materials. In order to 
protect metal containers from corrosion, they shall be either rubber lined or plastic-coated. 
NOTE Pressure build-up in the containers sh ould be prevented by suitable venting. 
 FDUS 925: 2012 
© UNBS 2012 – All rights reserved  5
 Annex A 
(normative)  
 
Method for determination of available chlorine content 
A.1 Principle 
The sample is added to acidified solution of potassium iodide and the released iodine is titrated with 
standard sodium thiosulphate solution to the usual starch end point. 
A.2 Reagents 
A.2.1 Acetic acid, glacial 
A.2.2 Potassium iodide (KI), crystals, iodate free A.2.3 Sodium thiosulphate (Na
2S2O3.5H 2O), standard solution   
Dissolve 25 g of Na 2SO 3 crystals in freshly boiled and cooled water and dilute to 1 L. The solution is more 
stable if the glassware is cleaned with sulphuric-chromic acid and thoroughly rinsed with water. 
Standardize against potassium iodate (KIO 3) as follows: Weigh out accurately 3.567 g of dry KIO 3 and 
transfer to a 1 L volumetric flask. Dissolve with water, make up to the mark and mix thoroughly. This 
solution will be exactly 0.1000 N. To standardize the Na 2S2O3 solution, carefully pipette a 50 mL aliquot of 
the KIO 3 solution into a 250 mL Erlenmeyer flask and dilute to 100 mL with water. Add 1 g of KI crystals. 
When it is dissolved, add 15 mL of 1.0 N hydroc hloric acid and titrate immediately with the Na 2S2O3 
solution. When the solution becomes light yellow, add 1 mL of starch indicator solution and complete the titration to the disappearance of the bl ue colour. Standardize at least monthly. 
Calculate the normality of the Na
2S2O3 solution as follows: 
Normality, N 1 = (50x0.1)/A 
where, 
A is the value of Na 2S2O3. Solution, in millilitres, required for titration of KIO 3 solution . 
A.2.4  Starch indicator solution , mix 0.5 g of soluble starch with 5 mL of cold water and add to 95 mL  
of boiling water. Mix, cool and store in a sterilized bottle. Replace frequently or add 0.1 % salicylic acid to minimize deterioration. 
A.3 Procedure 
Dissolve 2 g to 3 g of KI crystals in to 50 mL  of water in a 250 mL  Erlenmeyer flask. Add 10 mL of acetic 
acid. Then pipette the aliquot of sample into the solu tion keeping the tip of the pipette beneath the surface 
of the solution until drained. Titrate at once with 0.1 N  Na2S2O3 solution until the iodine colour is nearly 
gone then add 1 mL  of starch indicator solution and complete the titration to the disappearance of the 
iodine colour. Record the titration as A. FDUS 925: 2012 
6 © UNBS 2012 – All rights reserved
 A.4 Calculations 
A.4.1  Calculate the available chlorine as follows:  
Available chlorine as CI, g/L  = ()
VAN 35.461× 
A.4.2  Calculate the sodium hypochlorite content as follows;  
Sodium hypochlorite (NaOCI), g/L  = ()
VAN 37.221×  
where 
A is the volume, in millilitres, of Na 2S2O3 solution required for titration of the sample ; 
N1 is the normality of the Na 2S2O3 solution; and 
V is the volume, in millilitres, of original sample in aliquot used. FDUS 925: 2012 
© UNBS 2012 – All rights reserved  7
 Annex B  
(normative) 
 
Method of determination of sodium hydroxide content 
B.1 Principle 
A sample is added to a neutralised, mixed solution of barium chloride and hydrogen peroxide, which 
precipitates any carbonate and reduce s the hypochlorite to chloride. The free alkali is then titrated with 
standard hydrochloric acid using phenolphthalein indicator. 
B.2 Reagents 
B.2.1 Barium chloride solution (100g/L) , dissolve 100 g of chemically pure barium chloride 
(BaCI 2.2H 2O) in distilled water and dilute to one litre  with distilled water. Filter the solution if turbid. 
B.2.2 Hydrochloric acid , standard (0.1 N), prepare a 0.1 N solution of hydrochloric acid (HCI) and 
standardize against primary standard solution carbonate and methyl red mixed indicator. 
B.2.3 Hydrogen peroxide , approximately 3%. 
B.2.4 Phenolphthalein indicator solution  (0.5 g/100 me), dissolve 0.5 g of phenolphthalein in 60 mL 
of 95 % ethyl alcohol and dilute to 100 L with sodium hydroxide solution. 
Dissolve 4.0 g of chemically pure sodium hydroxide in distilled water and dilute to 1 L  with distilled water. 
B.3 Procedure  
Place 50 mL  of barium chloride solution and 30 mL of hydrogen peroxide in a 250 mL  Erlenmayer flask (or 
6.in porcelain dish). Add 10 drops of phenolphthalein  indicator solution and neutralize with sodium 
hydroxide solution. Introduce into this neutral mixtur e 10 mL of the liquid bleach, shake or stir vigorously 
for 1 min and titrate the sodium hydroxide solution with 0.1 N hydrochloride acid until the pink colour 
disappears. 
B.4 Calculation  
Calculate the free alkali as NaOH as follows: 
Free alkali as NaOH, g/L = ()
VLN 40 2×
 
where 
L is the volume, in millilitres, of hydrochlor ic acid solution used in the titration ; 
N2 is the normality of the hydrochloric acid solution; and 
V is the volume, in millilitres, of original sample used.  
 FDUS 925: 2012 
8 © UNBS 2012 – All rights reserved
 Annex C  
(normative) 
 
Method of determination of insoluble matter 
C.1 Apparatus  
C.1.1 Gooch crucible  
C.1.2 Balance  C.1.3 Oven  
C.2 Procedure 
Pour approximately 100 mL of the sodium hypochlorite solution into a tared 400 mL beaker placed on a 
laboratory platform balance and weigh to the nearest 0.1 g. Add 100 mL of distilled water and mix thoroughly. Filter through a tared Gooch crucible. Wash  the beaker and crucible with distilled water. Dry 
the crucible to a constant weight at 100 °C - 105 °C. 
C.3 Calculation 
Percent insoluble matter = 100
sample of Gramsresidue of Grams×  
  
 
 
 
 
 
 
 FDUS 925: 2012 
© UNBS 2012 – All rights reserved  9
 Certification marking 
Products that conform to Uganda standards may be  marked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below.  
The use of the UNBS Certification Mark is gove rned by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those licens ed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in co njunction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation to a product is an assurance that the goods comply with the 
requirements of that standard under a system of supervision, control and  testing in accordance with the 
certification mark scheme of the Uganda National  Bureau of Standards. UNBS marked products are 
continually checked by UNBS for conformity to that standard.  
Further particulars of the terms and conditions of  licensing may be obtained from the Director, Uganda 
National Bureau of Standards.  
 
 FDUS 925: 2012
 
ICS nn.nnn.nn  
Price based on nn pages 
© UNBS 2012– All rights reserved