CDC 6 (959) DTZS 
ICS 71.100.80 
© TBS 2022                                                                                                2nd Edition  
   
  
 
DRAFT TANZANIA STANDARD  
 
 
Sodium dichloroisocyanurate - Specification 
 
 
 
   
 
 
 
 
 
 
  
  
  
  
  
  
 
 
 
 
  
  
  
  
  
 
 
TANZANIA BUREAU OF STANDARDS 
                            
 
 
 
 CDC 6 (959) DTZS 
ICS 71.100.80 
© TBS 2022                                                                                                2nd Edition  
 Foreword  
  
This Draft Tanzania Standard is being developed by the Water Quality Technical Committee 
under supervision of the Chemical Division Standards Committee and it is in accordance with 
the procedures of the Bureau. 
  
This Tanzania Standard has been prepared with assistance drawn from:  
  
BS EN 12931: 2015 Chemicals used for treatment of water intended for human 
consumption – Sodium dichloroisocyanurate, anhydrous , published by European 
Union. 
 
IS 15773:2008 Sodium dichloroisocyanurate (NaDCC) – Specification Published by 
the Bureau of Indian Standards.  
 
In reporting the result of a test or analysis made in accordance with this Tanzania Standard, if 
the final value, calculated or observed is to be rounded off, it shall be done in accordance with 
TZS 4 (see clause 2).  
  
  
  
  
  
  
  
  CDC 6 (959) DTZS  
© TBS – All rights reserved  3 
 DRAFT TANZANIA STANDARD                        CDC 6 (959) DTZS  
  
Sodium dichloroisocyanurate - Specification 
 
1. Scope 
 
This Draft Tanzania Standard specifies requirements, sampling and test methods for Sodium 
dichloroisocyanurate used for water treatment intended for human consumption.  
It covers both dihydrate and anhydrous Sodium dichloroisocyanurate. 
 
2. Normative references 
 
TZS 59/ ISO 3696 Water for analytical laboratory use - Specification   
TZS 1445 / ISO 3165 Sampling of chemical products for industrial use -Safety in 
sampling. 
 
TZS 1444/ ISO 6206 Chemical products for industrial use - Sampling - Vocabulary. 
TZS 1443 / ISO 8213 Chemical products for industrial use - Sampling techniques – 
Solid chemical products in the form of particles varying from powders to coarse 
lumps. 
 
3. Terms and definitions 
 
For the purposes of this document terms and definitions given in TZS 1444/ ISO 6206 and the 
following apply.  
ISO and IEC maintain terminological databases for use in standardization at the following 
addresses: 
— ISO Online browsing platform: available at http://www.iso.org/obp  
water intended for human consumption 
all water either in its original state or after treatment, intended for drinking, cooking, food 
preparation or other domestic purposes, regardless of its origin and whether it is supplied 
from a distribution network, from a tanker, or in bottles or containers 
 
4 Requirements  
  
4.1 General requirements 
4.1.1 Descriptions  
 
4.1.1.1 Chemical name ; 1-sodium - 3, 5-dichloro -1, 3, 5-triazine - 2, 4, 6-trione 
4.1.1.2 Synonym or common name ; Sodium dichloroisocyanurate. 
4.1.1.3 Relative molecular mass ; 219.98 (Type 2) or 256.02 (Type 1)  
4.1.1.4 Empirica l formula; C3N3O3Cl2Na or C 3N3O3Cl2.2H2O 
4.1.1.5 Chemical  formula; C3Cl2N3NaO3 
4.1.1.6 Commercial form ; The product is available in various granular forms or 
tablets. 
 
 
 CDC 6 (959) DTZS  
© TBS – All rights reserved  44.1.2 Physical-chemical  properties   
 
4.1.2.1 The material shall be of two types; 
a) Type 1 (Sodium Dichloroisocyanurate, Dihydrate) 
b) Type 2 (Sodium Dichloroisocyanurate, Anhydrous) 
 
4.1.2.2 Sodium dichloroisocyanurate shall be white coloured in form of granular solid 
or tablets with chlorinous odour.  
 
4.1.2.3 The density of Sodium dichloroisocyanurate is approximately 0.9 g/cm3 
4.1.2.4 The material is a strong oxidant, it is corrosive and hygroscopic; Sodium 
dichloroisocyanurate decomposes to hydrochloric and cyanuric acid. When dissolved 
in excess water it liberates chlorine by hydrolysis. 
 
4.2 Specific requirements 
 
4.2.1 The material, when tested according to the methods prescribed in Annexes A, B, and C 
shall comply with the specific requirements given in Table 1. 
 
Table 1 Specific requirements for Sodium dichloroisocyanurate 
 
S/N Characteristic  Requirement  Method of test  
Type 1 Type 2 
i. Available chlorine content,  
% wt, min  55  62 
 Annex A  
ii. Sodium chloride content  
%, (m/m),  max   
0.05 Annex B 
iii. Water content, % (m/m), max  
 __ 3 Annex C 
 
4.2.2 Toxic substances  
The content of toxic substances shall comply with the requirements specified in Table 2.  
  
Table 2 — Toxic substances  
 
 Maximum limit mg/kg of  
Element  product  
Arsenic (As)  0.05 
Cadmium (Cd)  0.01 
Chromium (Cr)  0.05 
Mercury (Hg)  0.001 
Nickel (Ni)  0.02 
Lead (Pb)  0.01 
Antimony (Sb)  0.005 
Selenium (Se)  0.01 
 
 
 
 
 
 
 
 CDC 6 (959) DTZS  
© TBS – All rights reserved  55 Packaging and marking  
  
5.1 Packaging  
 
5.1.1 The granular product shall be packed in clean, dry and tight containers, without faults, 
made of material which do not affect the contents  
5.1.2 The tablets shall be wrapped each individually enabling retailers to sell single tablet,  
 
5.2 Marking  
The following information shall be marked legibly and indelibly on the container:  
a) name of the product as ‘SODIUM DICHLOROISOCYANURATE’.  
b) type of product i.e. dihydrate or anhydrous  
c) the name and address of manufacturer.  
d) net content.  
e) batch or code number.  
f) nominal available chlorine content.  
g) dates of manufacturer and best before.  
h) instruction for handling, storage and use. 
i) first aid instructions. 
j) the words “STORE IN COOL DRY PLACE AWAY FROM DIRECT SUNLIGHT‟ 
k) hazard warning in symbol or words   
 
6. Sampling   
 
Sampling shall be done as per TZS 1443/ISO 8213 while observing the general 
recommendations as given in TZS 1445/ISO 3165 and TZS 1444/ISO 6206 
 
7. Testing  
  
Methods of tests for Sodium dichloroisocyanurate shall be as prescribed in the annexes.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CDC 6 (959) DTZS  
© TBS – All rights reserved  6 
Annex A  
(Normative)   
Determination of available chlorine  
  
A.1 Principle  
  
The available chlorine is determined by measuring active chlorine in the sample. The 
oxidizing chlorine reacts with potassium iodide releasing iodine, which is then titrated with 
sodium thiosulphate standard volumetric solution in the presence of starch indicator solution.  
  
A.2 Reagents   
  
All reagents shall be of recognized analytical grade and the water used shall conform to grade 
according to TZS 59.  
  
A.2.1 Potassium iodide crystals (KI)   
  
A.2.2 Glacial acetic acid  
  
A.2.3 Sodium thiosulphate standard volumetric solution, c (Na 2S2O3.5H2O) = 0.1 mol/L 
  
A.2.3.1 Dissolve 24.8 g of Na 2S2O3.5H2O in water.  Add 0.5 mL of chloroform as preservative, 
dilute to volume with water in a 1000 mL one-mark volumetric flask and mix thoroughly.  
  
A.2.3.2 Weigh to the nearest 0.1 mg (160 ± 10) mg (m) primary potassium dichromate into 
tarred glass beaker. Place the contents of the beaker in a 500 ml stoppered conical flask, add 
100 mL of water and (2 ± 0.5) g potassium iodide and stir to dissolve. Add (15 ± 1) mL of 
hydrochloric acid solution (dilute 1+1 by volume) swirl and allow standing for 5 min. Titrate 
with the Sodium thiosulphate solution until the solution is pale yellow. Add (5 ± 1) mL of starch 
solution and titrate to the end point, i.e. to the disappearance of the blue-black colour. Record 
the volume (V) used. 
 
A.2.3.3 The concentration, C, of the Sodium thiosulphate standard volumetric solution 
(Na2S2O3.5H2O), expressed in moles per litre, is given by the following equation:                    
    
C  
    
where  
m  is the mass, in milligrams, of potassium dichromate (K 2Cr2O7) weighed;  
  
V  is the volume, in millilitres, of the sodium thiosulphate standard volumetric solution      
used.  
  
49.0317 is the molar mass, in grams per mole of potassium dichromate. 
 
A.2.4  Starch solution, 1% (m/m)  
  
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 point.  Keep the solution cool 
and use it within one week.  
  
NOTE – Commercial indicators for iodine titration exist and can be used in 
place of the described starch solution provided that their efficiency has been 
previously tested.  CDC 6 (959) DTZS  
© TBS – All rights reserved  7  
  
A.3 Apparatus  
  
Ordinary laboratory apparatus glassware.  
  
  
A.4 Procedure  
  
A.4.1 Test portion  
  
Weigh, to the nearest 0.1 mg, 0.25 g of the laboratory sample (m 0) into a tarred stoppered 
weighing bottle. 
  
A.4.2  Determination  
  
Transfer the test portion to a 200 mL volumetric flask. Add 10 mL of water and 10 mL glacial 
acetic acid, stir for 5 min. and then add 100 mL of water and 2 g of potassium iodide, mix to 
dissolve and wait for 10 min. Titrate with the Sodium thiosulphate standard volumetric solution 
to a light yellow colour. Add 5 mL of the starch solution and continue titration to the 
disappearance of the blue-black colour. Record the volume (V 1) of the Sodium thiosulphate 
standard volumetric solution used. 
  
A.5  Expression of results  
  
The chlorine (Cl 2) content, C 1, expressed as a percentage by mass, is given by the following 
equation:  
     C 1   
  
 
where  
  
V1 is the volume, in millilitres, of the Sodium thiosulphate solution used for the titration; 
 
 C    is the concentration, in moles per litre, of the Sodium thiosulphate standard 
volumetric solution;  
  
m1 is the mass, in grams, of the test portion;   
  
0.003545 is the mass, in grams, of chlorine (Cl 2) corresponding to 1.00 mL of Sodium 
thiosulphate solution, c (Na 2S2O3.5H2O) = 0.1 mol/L; 
 
 C is the actual concentration, expressed in moles per litre of the Sodium thiosulphate 
standard volumetric solution. 
 
 
 
 
 
 
 
 
 CDC 6 (959) DTZS  
© TBS – All rights reserved  8Annex B  
(Normative) 
Determination of Sodium chloride 
 
B.1 General  
  
This method applies to products with Sodium chloride contents in the range of 0 % (m/m) to 
0.05 % (m/m). 
 
  
B.2 Principle  
 
The anhydrous Sodium dichloroisocyanurate is acidified and then digested to remove all 
traces of available chlorine. Sodium is analysed in solution by atomic absorption 
spectrometry. 
  
  
B.3 Reagents  
  
All reagents shall be of recognized analytical grade and the water used shall conform to grade 
according to TZS 59. 
  
B.3.1 Sulphuric acid, concentrated, (H 2SO4) 95 % (m/m) minimum. 
  
B.3.2 Sodium standard solution (1 000 µg/mL)  
  
Weigh, 2.5421 g of Sodium chloride that has been previously dried for 1 h at 110 0C. Dissolve 
in water and dilute to volume with water to a 1 000 mL volumetric flask and make up to the 
mark. Mix well. 
 
B.4 Apparatus  
  
Ordinary laboratory apparatus and glassware, together with the following:  
  
B.4.1 Atomic absorption spectrometer equipped with Sodium hollow cathode lamp  
  
B.4.2 Hot plates  
  
 
  
B.5 Procedure  
  
B.5.1 Test portion  
  
Weigh, to the nearest 0.1 mg, 2.5 g of the laboratory sample (m3) into a tarred stoppered 
weighing bottle. 
  
B.5.2 Determination  
  
Transfer the test portion to a 250 mL beaker. Dilute with 25 mL water. Mix and then add 10 
mL of the concentrated sulphuric acid and place on a hot plate and boil until the salt begins to 
precipitate. Rinse the inside of the beaker with water. 
  
 
 
 CDC 6 (959) DTZS  
© TBS – All rights reserved  9Transfer to a 250 mL volumetric flask and dilute to the mark with water and mix well. Measure 
the absorbance of the solution on the atomic absorption spectrometer with Sodium hollow 
cathode lamp at a wavelength of 330.2 nm with slit setting at ‘’4’’ using an acetylene flame. 
 
B. 5.3 Calibration 
Transfer accurately from the Sodium standard solutions 1.0 mL, 2.0 mL, 3.0 mL, 4.0 mL, 5.0 
mL and 10.0 mL portions to series of 100 mL volumetric flasks, dilute to the mark with water 
and mix well. Prepare a calibration curve. 
  
Measure the absorbance of each calibration solution as described in B.2.2.5.2, and prepare a 
calibration graph. 
 
B 6 Expression of results 
 
TheSodium chloride content, (C 2), expressed as a percentage by mass, % (m/m) of product is 
given by the following equation:  
  
  
    
          
 
 
 
where  
  
m3 is the mass in grams, of the test portion;  
  
C is the concentration, in micrograms per millilitre, of Sodium in the test portion as determined 
from the calibration graph.  
  
  
  
  
 
 
 
 CDC 6 (959) DTZS  
© TBS – All rights reserved  10Annex C  
(Normative) 
Determination of Water content 
  
  
C.1 Principle  
  
Water content in Sodium dichloroisocyanurate is determined by the mass loss after heating in 
an oven. The temperature is set at a low level because Sodium dichloroisocyanurate can 
loose chlorine on heating.  
  
C.2 Apparatus  
  
Oven made of Aluminium, provided with a means of circulating the air inside 
  
C.3 Procedure  
  
Weigh 10 g of the laboratory sample (m 1), to the nearest 0.001g, in a glass-evaporating dish 
(diameter 150 mm). Put it in the ventilated oven at 105 0C for 4 h. Allow to cool in a desiccator 
and weigh again ( m2). 
 
C.4  Expression of results  
  
The water content, w 1, expressed as a percentage by mass (% (m/m)), is given by the 
following equation: 
 
 
 
 
 
where 
           m1 is the mass, in grams, before drying; 
           m2 is the mass, in grams, after drying.