CDC 6 (121) DTZS 
© TBS 2021                                                                                                Second Edition 2021 
   
  
 
 
 
 
   
 
 
 
 
 
 
Calcium hypochlorite used for disinfection of water intended 
for human consumption – Specification  
 
 
   
  
  
  
  
  
  
  
  
  
  
  
 
  
  
  
  
  
  
  
 
 
TANZANIA BUREAU OF STANDARDS   
                                                                               
  
 DRAFT TANZANIA STANDARD    CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
  
 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 900:1999, Chemicals used for treatment of water intended for human 
consumption – Calcium hypochlorite , published by the European Community (EC);  
  
SABS 296:1998, Specification for calcium hypochlorite , published by the South  
African Bureau of Standards;  
  
KS 1290(Part 4): 2007, Chemicals used for treatment of water intended for human 
consumption – Part 4: Calcium Hypochlorite , published by the Kenya Bureau of 
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 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
  
    
   
DRAFT TANZANIA STANDARD                    CDC 6(121) CD2  
  
  
Calcium hypochlorite used for disinfection of water intended for human 
consumption – Specification  
  
1 Scope  
  
This Draft Tanzania Standard specifies requirements, sampling and tests method for calcium 
hypochlorite used in disinfection of water intended for human consumption.  
 
  
2 Normative references  
  
The following referenced documents are indispensable for the application of this document. 
The latest edition of the referenced document (including any amendments) applies;  
 
TZS 59 / ISO 3696 Water  for analytical laboratory use – Specification and test 
methods   
  
TZS 4 Rounding off numerical values  
  
  
3 Terms and definitions 
 3.1. 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 ; Calcium hypochlorite  
 
4.1.1.2 Relative  molecular mass ; 142.99  
  
4.1.1.3 Empirical  formula; Ca(OCI) 2.  
  
4.1.1.4 Chemical  formula; Ca(OCI) 2 or CaCl 2O2 
  
 
 
 
 
 
 
 
 
 CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
 4.1.2 Physical properties  
  
4.1.2.1 Calcium hypochlorite shall be in the form of white or yellowish-white free-flowing 
granules, powder or tablets.  
 
4.1.2.2 Calcium hypochlorite granular powder or granules shall be substantially free from 
lumps. Not more than 10% of the powder shall pass a 100-mesh µm screen. It shall not 
contain any dirt or other foreign material.  
  
 4.1.2.3 Calcium hypochlorite tablets shall be uniform in shape. The weight of the tablets shall 
not vary by more than 5% from the average value stated on the label. Not more than 2% of 
the tablets shall be broken. 
  
4.1.3 Calcium hypochlorite 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 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 Calcium hypochlorite 
 
S/N Characteristic Requirement  Method of test  
i. Available chlorine content,  
 
%, (m/m), min   65 
 annex A  
ii. Sodium chloride content  
%, (m/m),  max  18 annex B 
iii. Water Insoluble matter, % (m/m) , max 4 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)  10  
Cadmium (Cd)  1  
Chromium (Cr)  6 
Mercury (Hg)  0.02  
Nickel (Ni)  3  
Lead (Pb)  4  
Antimony (Sb)  5  
Selenium (Se)  1  
 
NOTE  For the purpose of this standard, “toxic substances” are those defined in the EU Directive 80/778/EEC of 
15 July, 1980 ( see 1) 
 
 
 
 
 
                                       
1) Chemical Abstracts Service Registry Number  CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
  
 5 Packing and marking  
  
5.1 Packing  
  
Calcium hypochlorite shall be packed in a suitable opaque airtight container that withstand 
normal handling and transportation and that will prevent leakage, contamination and loss of 
percentage purity of the product. 
 
In order that purity of the product is not affected, the means of delivery shall not have been 
used previously for any different product or it shall have been specially cleaned and prepared 
before use.  
 
5.2 Marking  
  
The following information shall be marked legibly and indelibly on the container at minimum;  
  
a) name and formula of the product as ‘CALCIUM HYPOCHLORITE’ (Ca(OCI) 2 or 
CaCl2O2)  
b) the name and address of manufacturer.  
c) net content.  
d) batch or code number.  
e) nominal available chlorine content.  
f) dates of manufacture and best before.  
g) instruction for use and Handling. 
h) first aid instructions. 
i) the words ‘STORE IN COOL PLACE AWAY FROM DIRECT SUNLIGHT’ 
j) hazard warning in symbol or words   
 
5 Sampling   
Sampling for Calcium hypochlorite shall be done as per Annex D 
 
6 Testing  
  
Methods of tests for Calcium hypochlorite shall be as prescribed in the annexes.  
  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
 Annex A  
(normative)   
Determination of available chlorine and calcium hypochlorite content  
  
  
A.1 General  
  
This method applies to products with available chlorine contents within the range of 40% 
(m/m) to 70% (m/m).  
  
A.2 Principle  
  
Calcium hypochlorite reacts with potassium iodide to release iodine in the presence of acetic 
acid.  The iodine is titrated with sodium thiosulphate standard volumetric solution in the 
presence of starch indicator solution.  
  
  
A.3 Reagents   
  
All reagents shall be of analytical grade and the water used shall be distilled water.  
  
A.3.1 Potassium iodide crystals (KI)   
  
A.3.2 Glacial acetic acid  
  
A.3.3 Sodium thiosulphate standard volumetric solution, c (Na 2S2O3.5H2O) = 0.1 mol/L 
  
A.3.3.1 Dissolve 24.8 g of Na 2S2O3.5H2O in water (as per TZS 59).  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.3.3.2 To standardize; weigh, to the nearest 0.1, mg (160 ± 10) mg (m) of primary standard 
potassium dichromate into a 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 of potassium iodide and stir 
to dissolve.  Add (15 ± 1) mL of hydrochloric acid solution (diluted 1:1 by volume), swirl and 
allow to stand 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.3.3.3 The concentration, C, of the sodium thiosulphate standard volumetric solution  
(Na2S2O3.5H2O), expressed in moles per litre is given by the following equation:        
                    
   C  =௠
௏ ௑ ସଽ.଴ଷଵ଻  
    
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.  
  
 
 
 
 CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
 A.3.4  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.  
  
A.4 Apparatus  
  
Ordinary laboratory apparatus glassware, together with the following: Laboratory sonic 
vibrator.  
  
  
A.5 Procedure  
  
A.5.1 Test portion  
  
Weigh to the nearest 0.1 mg, 3.5 g of the laboratory sample (m 1) into a tarred stoppered 
weighing bottle.  
  
A.5.2  Determination  
  
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 solution.  
Dilute to the mark with water.  
  
Place a magnetic 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.  
  
Add 100 mL of water (as per TZS 59) and 2 g of potassium iodide and mix to dissolve.  Add 8 
mL of glacial acetic acid, stir and titrate immediately with the sodium thiosulphate standard 
volumetric solution to a light yellow colour.  Add 3 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.6  Expression of results  
  
The chlorine (Cl 2) content, C 1, expressed as a percentage by mass, is given by the following 
equation:  
   
C1   =௏ଵ ௑ ஼ ௑ ଷହ.ସହଷ ௑ ଶ଴ ௑ ଵ଴଴ 
௠భ 
 
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 milligrams, of the test portion;   
  CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
 35.453 is the mass in milligrams of chlorine (Cl 2) corresponding to 1,00 mL of sodium 
thiosulphate solution c (Na 2S203.5H20) = 1.000 mol/L.  
  
The Ca (CIO) 2 content, C 2, expressed as a percentage by mass of product, is given by the 
following equation:  
  
        
C2  =  ஼భ ௫ ଷ.ହ଻ସ଺ 
 ଷ.ହସହଷ  
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
 Annex B  
(normative)   
Determination of sodium chloride  
 
B.1 General  
  
This method applies to products with sodium chloride contents in the range 15% (m/m) to 
25% (m/m).  
  
  
B.2 Principle  
  
Calcium hypochlorite is acidified, digested to remove all traces of available chlorine, and 
diluted to a known volume.  Sodium is analyzed in solution by atomic absorption 
spectrometry.  
  
  
B.3 Reagents  
  
All reagents shall be of analytical grade and the water used shall be distilled water.  
  
B.3.1 Hydrochloric acid, concentrated, HCI  
  
B.3.2 Sodium standard solution (1000 µg/mL)  
  
Weigh 2.5421 g of sodium chloride that has been previously dried for 1 h at 110°C.  Dissolve 
in water and dilute to 1 l.  Mix well.  
  
B.3.3 Commercial iodide starch test paper  
  
NOTE – Provided that its efficiency has been previously tested.  
  
  
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.4.3 Laboratory sonic vibrator  
  
  
B.5 Procedure  
  
B.5.1 Test portion  
  
Weigh, to the nearest 0.1 mg, 3.5 g of the laboratory sample (m 3) into a tarred stoppered 
weighing bottle.  
  
B.5.2 Determination  
  
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 occasionally until the sample is in solution. Dilute to 
the mark with water.  CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
   
From the prepared solution, transfer accurately 25 mL to a 150 mL beaker. Add 10 mL of the 
concentrated hydrochloric acid and place on a hot plate.   
  
Boil to reduce the volume to 25 mL or, until the salt begins to precipitate, rinse the side of the 
beaker with water and test for available chlorine using the iodide-starch test paper. If chlorine 
is still present add 50 mL of water and reduce the volume again to 25 mL. Rinse the side of 
the beaker with water and test for available chlorine.  
  
Repeat the procedure until available chlorine is not present, then cover the beaker and digest 
for 1 min, allow cooling then transferring to a 100 mL volumetric flask and diluting to the mark 
with water.  
  
Measure the absorbance of the solution on the Atomic Absorption Spectrometer (AAS) with 
sodium hollow cathode lamp at a wavelength of 330.2 nm with slit setting at “4” using an air-
acetylene flame.  
  
B.5.3 Calibration  
  
Transfer accurately from the sodium standard solution 1.0 mL, 2.0 mL, 3.0 mL, 4.0 L, 5.0 mL, 
10.0 ml and 20.0 ml portions to a series of 100 ml volumetric flasks, dilute each to the mark 
with water and mix well.  Prepare a calibration blank.  
  
Measure the absorbance of each calibration solution as described in B.5.2 and prepare a 
calibration graph.  
  
  
  
B.6 Expression of results  
  
The sodium chloride content, (C 4), expressed as a percentage by mass of product, is given by 
the following equation:  
  
    
C4   =஼ ௫ ଵ଴଴ ௫ ଶ଴ ௫ ଶ.ହସଶଵ 
௠య ௫ ଵ଴ ଴଴଴ 
          
  
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 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
 Annex C  
(normative)   
Determination of water-insoluble matter  
  
  
C.1 Principle  
  
A representative sample of calcium hypochlorite is dissolved in water. The insoluble matter is 
separated by filtration then dried and weighed.  
  
  
C.2 Apparatus  
  
Ordinary laboratory apparatus and glassware together with the following:  
  
C.2.1 Sintered glass crucible of porosity P40 (pores size between 16 µm to 
40 µm).  
  
C.2.2 Oven capable of being controlled at (105 ± 3) °C.  
  
  
C.3 Procedure  
  
Weigh approximately 10 g of the representative sample (m 4) to the nearest ± 0.01 g and 
dissolve in 1000 ml of water by stirring for 30 min. Then filter the solution under vacuum 
through a dried and weighed glass filter.  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 until the mass remains constant and weigh it (m 5) after cooling in a dessicator.  
 
C.4  Expression of results  
  
The insoluble matter expressed as percentage by mass (% (m/m)), C 5 in the product is given 
by the following equation:  
  
                  C 5  =௠ఱ
௠ర 𝑋 100                     
                                        
where   
  
m5 is the mass, in grams, of the residue;  
m4 is the mass, in grams, of the test portion.  
 
 CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
  
Annex D 
(Normative) 
 
Sampling 
 
  
D.1 Sampling.  
  
The following sampling procedure shall be applied in determining whether a lot complies with 
the relevant requirements of the specification. The samples so drawn shall be deemed to 
represent the lot for the respective properties.  
  
D-2 From  the lot take at random at least four containers and, after inspecting each of them, 
use one container for testing for compliance with the requirement for shelf life.  After 
thoroughly mixing the contents of each of the remaining containers, by taking an 
approximately equal quantity of material from each container, and immediately placing it in 
one clean, dry, air-tight glass or plastic container obtain enough material to provide a 
composite sample of total mass at least 1.5 kg.  
  
D-3 Clearly mark the name of the product, the manufacturer’s name or trademark, the batch 
identification and the date of sampling on the sample container.  
  
  
D-4 Compliance with the specification  
  
The lot shall be deemed to comply with the requirements of the specification if, after 
inspection and testing of the samples taken in accordance with D.1, no defective is found.  
  
D-5 Inspection   
Inspect the containers taken in accordance with D.1 for compliance with the requirements in 
clause 4.  
  
 
  
  
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
  
Annex E  
  (Informative)   
 
Labelling – Transportation – Marking  
  
  
E.1 Risk and safety labelling  
  
The following labelling requirements applies to calcium hypochlorite:  
  
a) Symbols indications of danger.  
  
O: Oxidizing  
C: Corrosive  
  
b) Nature of special risks attributed to dangerous substances  
  
R 8:   Contact with combustible material may cause fire  
R 31: Contact with acids liberates toxic gas  
R 34: Causes burns  
  
c) Safety advice concerning dangerous substances  
  
S 2: Keep out of children  
S 26: In case of contact with eyes, rinse immediately with plenty of water and seek 
medical advice  
S 43: In case of fire, use air-independent respiratory equipment for fighting  
  
E.2 Transportation regulations and labelling  
  
Calcium hypochlorite is listed as;  
      
 . UN number 17482) for granular, calcium hypochlorite mixture, dry  
 . UN number 17482 for tablets, calcium hypochlorite, dry  
  
NOTE – The above products contain less than 5.5% (m/m) water and more than 39 % 
(m/m) available chlorine.  
 
RID3: class 5.1  
ADR4; class 5.1 
 IMDG5: class 5.1 
 IATA6: class5.1 
 
 
 
  
 
 
 
 
      
                      
   CDC 6 (121) DTZS 
 
© TBS 2021                                                                                                Second Edition 2021 
                                                   
 
  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1 
 
                                       
2 United Nations Number  
3   Regulations concerning carriage of dangerous goods by rail 
4 European agreement concerning the international carriage of dangerous goods by road  
5 International Maritime Transport of Dangerous Goods 
 6 International Air Transport Association