DRAFT UGANDA STANDARD  
  DUS 1963  
First  Edition  
2018-mm-dd  
 
 
 Reference number 
DUS 1963: 2018 
© UNBS 2018  
  
Caustic Soda (Sodium Hydroxide)—Specification  
 DUS 1963: 2018 
ii © UNBS 2018 – All rights reserved
 Compliance with this standard does not, of itself c onfer immunity from legal obligations 
A Uganda Standard does not purport to include all n ecessary provisions of a contract. Users are 
responsible for its correct application  
© UNBS 2018  
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 DUS 1963:2018 
© UNBS 2018 – All rights reserved  iii
 Foreword 
Uganda National Bureau of Standards (UNBS) is a par astatal under the Ministry of Trade, Industry and 
Cooperatives established under Cap 327, of the Laws  of Uganda, as amended.  UNBS is mandated to co-
ordinate the elaboration of standards and is  
(a) a member of International Organisation for Stan dardisation (ISO) and  
(b) a contact point for the WHO/FAO Codex Alimentar ius Commission on Food Standards, and  
(c) the National Enquiry Point on TBT Agreement of the World Trade Organisation (WTO). 
The work of preparing Uganda Standards is carried o ut through Technical Committees. A Technical 
Committee is established to deliberate on standards  in a given field or area and consists of key stake holders 
including government, academia, consumer groups, pr ivate sector and other interested parties.  
Draft Uganda Standards adopted by the Technical Com mittee are widely circulated to stakeholders and th e 
general public for comments. The committee reviews the comments before recommending the draft standard s 
for approval and declaration as Uganda Standards by  the National Standards Council. 
The committee responsible for this document is Tech nical Committee UNBS/TC ### , [name of committee] , 
Subcommittee SC ## , [name of subcommittee] . 
This second/third/… edition cancels and replaces the first/second/… edition (US nnn-n :yyyy ), which has been 
technically revised.  
US nnn consists of the following parts, under the g eneral title Introductory element — Main element :  
•  Part n: Part title  
•  Part [n+1]: Part title  
•  Part [n+2]: Part title  DUS 1963: 2018 
iv © UNBS 2018 – All rights reserved
 Introduction 
Sodium hydroxide (NaOH) solution, commonly known as  caustic soda, is produced through the electrolysis  of 
sodium chloride (salt) brine in diaphragm or membra ne cells. Chlorine and hydrogen are co-produced. Th e 
caustic soda solution may be clear or slightly clou dy in appearance, depending on the cell process use d. It 
readily absorbs carbon dioxide from the air. It is available commercially as 50% NaOH but other 
concentrations can be produced. 
Caustic soda has a wide variety of applications in many industries, including pulp and paper, aluminum , soaps 
and detergents, textiles, petrochemicals and chemic al processing. 
 DUS 1963: 2018 
v  
 Caustic Soda (Sodium hydroxide) — Specification 
1 Scope  
This Draft Uganda Standard specifies requirements, methods of test and sampling for caustic soda, pure  and 
technical grade. It covers both solid and lye form.  
It does not apply to sodium hydroxide for medical o r pharmaceutical use and sodium hydroxide for 
photographic use.  
2 Normative references  
The following referenced documents referred to in t he text in such a way that some or all of their con tent 
constitutes requirements of this document. For date d references, only the edition cited applies. For u ndated 
references, the latest edition of the referenced do cument (including any amendments) applies. 
FDUS ISO 979 Sodium hydroxide for industrial use -- Method of as say 
FDUS ISO 981: 1973 Sodium hydroxide for industrial use -- Determinatio n of chloride content -- Mercurimetric 
method 
FDUS ISO 3196:1975 Sodium hydroxide for industrial use -- Determinatio n of carbonates content -- Titrimetric 
method 
DUS 1966: 2018 Sampling and test for sodium hydroxide for industri al use Part 1. Determination of silica 
content 
DUS 1965:2018 Sampling and test for sodium hydroxide for industri al use — Part 2: Determination of copper 
content 
DUS 1964:2018 Standard Test Methods for Chemical Analysis of Caus tic Soda and Caustic Potash (Sodium 
Hydroxide and Potassium Hydroxide) 
3 Terms and definitions  
ISO and IEC maintain terminological databases for u se in standardization at the following addresses:  
— ISO Online browsing platform: available at http://www.iso.org/obp  
4 Grades  
There shall be two grades of the material, namely:  
a) Pure  
b) Technical  DUS 1963: 2018 
vi © UNBS 2018 – All rights reserved
 5 Requirements 
5.1  General Requirements 
a) The material shall be supplied in the form of ly e or solid (including flakes, blocks, sticks and pe llets).  
b) The material shall be free from foreign matter, dirt or other visible impurities.  
c) Caustic Soda Lye is a clear to slightly haze liq uid  
d) Relative Density of Caustic Soda Lye shall be su bject to an agreement between the purchaser and 
the supplier. 
5.2 Specific Quality Requirements 
The material shall comply with the requirements giv en in Table 1, when tested according to the methods  
prescribed therein. 
Table 1: Requirements for Caustic Soda 
Characteristic Pure Technical Method  
Lye Solid Lye Solid 
Sodium carbonate (as Na 2CO 3) 
percent by mass. Max  0.20 0.20 2.00 2.00 DUS 1964 
Chloride (as NaCl), percent by  
mass, Max   
0.10  
0.10  
  
 FDUS ISO 
981/ DUS 
1964 
Sulphates (as Na 2SO 4), percent by  
mass, Max  0.10 0.10 3.50 3.50 DUS 1964 
Silicates (as SiO 2), percent by mass, 
Max  0.02 0.02 —  DUS 1966 
Iron (as Fe), ppm, 
Max 10 10 350 350 DUS 1964 
Copper (as Cu), ppm, 
Max  1 1 — — DUS 1965 
Sodium hydroxide ( as NaOH ),  
percent by mass, on dry basis 99.50 99.50 95.00 95.00 FDUS ISO 
979 
Note; The requirements in table1 for the lye are ba sed on 50%m/m 
 
 
6 Sampling  
The material shall be sampled in accordance with An nex A  DUS 1963:2018 
© UNBS 2018 – All rights reserved  vii
 7 Packaging and labelling 
7.1 Packaging  
7.1.1   The caustic soda solid shall be packed in polyeth ylene bags or polyethylene lined gunny bags or stee l 
drums.. The solution shall be supplied in suitable tankers, tank cars or as agreed to between the purc haser 
and the supplier. 
7.1.2  The container shall be capable of being resealed s o as to avoid absorption of carbon dioxide and 
moisture from the atmosphere. 
7.1.3  These containers may then be packed in bulk packag es that shall contain only one size of 
container. 
7.1.4  Sodium Hydroxide from the same batch shall be pack ed in one container and, when relevant, in one 
bulk package. 
7.2  Labelling  
7.2.1  Containers  
Each container shall bear the following information  in prominent, legible and indelible marking: 
a) the manufacturer's name and address; 
b) Name of  product Caustic Soda (Sodium Hydroxide) , and the  
c) grade; 
d) cautionary directions regarding handling, use an d safe storage; 
e) Safety precautions 
f) Lot/batch Number; 
g) Net mass/Volume of the contents; and 
h) manufacturing and expiry date 
i) The containers shall be marked with the followin g caution note: ‘CORROSIVE- HANDLE WITH CARE’ 
 
7.2.2  Bulk packages/Tanker 
Consignment documents accompanying each road tanker  or tank car shall bear the following information i n 
prominent, legible and indelible marking: 
a) the information required in terms of 7.2.1(a) an d (b); 
b) the number of containers; and 
c)  the volume of the contents of each container.  DUS 1963: 2018 
viii © UNBS 2018 – All rights reserved
 Annex A 
(Normative  Reference) 
 
Sampling of caustic soda, pure and technical 
A.1  General Requirements of sampling 
A.1.1 Precautions shall be taken to protect the samples, the material being sampled, the sampling 
instrument and the containers for samples from adve ntitious contamination, particularly from absorptio n of 
water and carbon dioxide. 
A.1.2 To draw a representative sample, the contents of ea ch container selected from sampling shall be 
mixed thoroughly by suitable means. 
A.1.3 The sample shall be placed in clean, dry and air-ti ght alkali resistant glass containers. 
A.1.4 Each sample container shall be sealed air-tight aft er filling, and marked with full details of samplin g, the 
date of sampling and the batch number. 
A.2 scale of sampling 
A.2.1 Lot 
All the containers in a single consignment of the m aterial drawn from a single batch of manufacture sh all 
constitute the lot. If a consignment is declared to  consist of different batches of manufacture, the b atches shall 
be marked separately and the groups of containers i n each batch shall constitute separate lots. 
A.2.2 Samples shall be tested from each lot separately fo r judging the conformity of the material to the 
specified requirements. The number of container ( n) to be selected at random from lots of different s izes ( N) 
shall be in accordance with Table 2. 
A.2.3 The container shall be drawn at random from the lot , and to ensure randomness, the following 
procedure may be adopted; 
a) Arrange all the containers in the lot in a syste matic manner, and starting from any one, count them  as 
1,2 ……. up to r, where r is the integral part of N/n. Every rth container thus counted shall be included 
in the sample till the required number of container s specified in col 2 of Table 2 is taken out. DUS 1963:2018 
© UNBS 2018 – All rights reserved  ix
 Table 2 Number of Containers to be selected for Sam pling 
Lot Size Number of Containers to be Selected 
 
N 
 n 
3 to 50 3 
51 to 200  4 
201 to 400 5 
401 to 650 6 
651 to 1 000 7 
 DUS 1963: 2018 
x © UNBS 2018 – All rights reserved
 Bibliography 
1. BS 4130: 1984 Specification for Sodium hydroxide  (technical grades) 
2. IS 252:1999 Caustic Soda, Pure and Technical— Sp ecification  DUS 1963:2018 
© UNBS 2018 – All rights reserved  xi
 Certification marking 
Products that conform to Uganda standards may be ma rked with Uganda National Bureau of Standards 
(UNBS) Certification Mark shown in the figure below .  
The use of the UNBS Certification Mark is governed by the Standards Act, and the Regulations made 
thereunder. This mark can be used only by those lic ensed under the certification mark scheme operated by 
the Uganda National Bureau of Standards and in conj unction with the relevant Uganda Standard. The 
presence of this mark on a product or in relation t o a product is an assurance that the goods comply w ith the 
requirements of that standard under a system of sup ervision, control and testing in accordance with th e 
certification mark scheme of the Uganda National Bu reau 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.  
 
 CDUS 1963: 2018