CDC 7  (14) DTZS  
 
 
 
 
 
© TBS 2020                  First Edition 2020  
 DRAFT TANZANIA STANDARD  
 
 
 
 
 
 
 
 
Bleaching powder  (Calcium H ypochlorite)  – Specification  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
TANZANIA BUREAU OF STANDARDS  
 
 
 
 CDC 7 (14)  DTZS  
2 
  
Introduction  
Bleaching powder (chemical formula = CaOCl 2) with its chemical name as  Calcium 
hypochlorite  is synthesized by the action of chlorine gas (produced from the chlor -alkali 
process) on dry slaked lime. It  is a carrier of chlorine the ingredient most widely used for 
bleaching, whitening, sterilization, disinfectio n and environmental hygiene. Bleaching powder 
is a pale yellowish powder existing with a strong smell of chlorine.  
 
Among the uses of the bleaching powder  is for  bleaching  dirty clothes in the laundry, as 
a bleaching  agent for cotton and linen in the textile industry.  Also, it is a strong oxidizing 
agent, hence used as an oxidizer in many industries.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 CDC 7 (14)  DTZS  
©TBS 2020 – All rights reserved                                                                                              3  
Foreword  
 
This Draft Tanzania Standard is being developed by the Industrial and Laboratory Chemicals 
Technical Committee under supervision of the Chemical Division Standards Committee and it 
is in accordance with the procedures of the Bureau.  
 
In the preparation of this Tanzania Standard assistance has been drawn from:  
 
IS 1065 -1: 2019 Stable  bleaching powder  - Speci fication , Part 1: Household and 
Industrial use , published  by the Bureau of Indian Standards  
 
Acknowledgement is hereby made for the assistance derived from this source.  
 
In reporting the result of a test or analysis made in accordance with this Tanzania Standard, if 
the final value, observed or calculated is to be rounded off, it shall be done in accordance with 
TZS 4 rounding  off numerical values.    CDC 7  (14) DTZS  
 
 
©TBS 2020 – All rights reserved                                                                                                   
                                                                                                                                           
 DRAFT  TANZANIA STANDARD                                                                           CDC 7 ( 14) DTZS  
 
 
Bleaching powder  (Calcium Hypochlorite)  – Specification  
 
 
1 Scope  
 
This Draft Tanzania S tandard prescribes the requirements, sampling and test methods for  bleaching 
powder  intended for household and industrial use.  
 
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 Water for analytical laboratory use – Specification and test method  
 
3. Terms and definitions  
For the purpose of this standard, the follow ing definitions shall apply.  
 
3.1  
Available chlorine  
chlorine equivalent of the hypochlorite chlorine present in bleaching powder  
  
3.2 
Stab ility  
difference in the chlorine equivalent of the hypochlorite chlorine present in the sample before and  
after heating it for 2  hrs at 100 ± 2  °C.  
 
4. Requirements  
 
4.1 General requirements  
 
4.1.1  The bleaching powder shall be white to slightly  yellowish -white in appearance and shall be free 
from hard lumps and any visible impurities.  
 
4.1.2  The bleaching powder shall be dry and free-flowing . 
4.2 Specific requirements  
The material, when tested according to the methods prescribed in Annex, shall comply with the  
specific  requirements given in Table 1.  
 
Table 1 Specific requirements for bleaching powder . 
 
S/N Characteristic  Requirement  Method of test  reference 
to anne x 
1.  Available chlorine, percent by mass, min 32.0 A 
2.  Stability, loss of chlorine on the basis of 
initial  available chlorine, max 1/11 B 
3.  Moisture, percent by ma ss, max 0.5 C 
4.  Particle size (passing  throu gh 1.70 mm  
sieve ), percent by mass, min 99.0 D 
 
 
  
2 
  
5 Packing and Marking  
5.1 Packing  
The material shall be supplied in clean, dry and tight containers, without faults , made of material 
which do not  affect the contents.  
5.2 Marking  
Each package shall be securely closed and marked with the following information  in English and/or 
Kiswahili :  
 
a) Name of material   
b) Manufacturer's name  and address  
c) Recognized trade -mark, if any  
d) Net content  
e) Lot or batch number  
f) Date s of manufacture  and best before  
g) Safety precautions including relevant warning signs  
h) Instruction for storage and use  
 
 
6 Sampling   
 
Representative samples of the material shall be drawn and their conformity to this standard shall be 
determined in accordance with the method prescribed in  Annex E.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
©TBS 2020 – All rights reserved                                                                                              3  
Annex A   
(Normative ) 
 Determination of available chlorine  
 
 
A-1 Reagents  
 
A-1.1 Potassium Dichromate Solution - 0.1 N.  
carefully pulverize a quantity of potassium dichromate (K 2Cr2O7) and dry at 110 ± 5  °C to constant 
mass. Dissolve 4.904 g of the dried reagent in water to make exactly 1 L and mix thoroughly.  
 
A-1.2 Standard Sodium Thiosul fate Solution - 0.1 N  
Standardization of Sodium Thiosul fate Solution — In a 250 m L glass -stoppered flask, take 2 g  of 
potassium iodide and about 25 m L water to dissolve  it. Then add approximately 2 g of sodium 
bicarbonate  and 5 ml of hydrochloric acid. Just before the effervescence ceases, add 25 m L of 0.1 N 
potassium  dichromate solutio n and stopper the flask. When the effervescence ceases, allow the flask 
to stand for 10 min in a cool dry place.  Dilute with 50 m L of water and titrate against standard sodium 
thiosul fate solution till the liquid in the flask has assumed a yellowish green colour. Then add starch 
solution and continue with the addition of sodium thiosul fate solution until the blue colour is just 
discharge.  
 
A-1.3 Starch indicator —Triturate 1 g of starch with 10 m L of cold water and pour, with constant 
stirrin g, in to 200 m L boiling water. Allow to settle and use the clear supernatant liquid.  
 
A-1.4 Potassium Iodide, solid  
 
A-1.5 Glacial Acetic Acid  
 
A-2 Procedure  
Weigh about 2.5 g of the sample , add small amount of water  and grind in a mortar till a smooth paste 
is formed.  Add 15 to 25 mL of water and decant off the fine part into a 250  mL flask. Again, grind the 
material left behind  and repeat the process of decanting off till no gritty material is left. Wash the 
pestle and mortar in the same flask. Make up the solution to 250 mL. Take 25 mL of this solution, add 
2 g of potassium iodide and 100 mL of water followed by 2 m L of glacial acetic acid. Titrate it against 
the standard sodium thiosul fate solution till the pale -yellow colour  disappears . At this stage add 
starch indicator and continue the addition of standard sodium thiosul fate solution till the blue colour 
discharges.  
 
A-3 Calculation  
Available chlorine, percent by mass = 𝐴 × 𝑁 × 35.46
𝑀 
 
Where,  
A = volume in ml of standard thiosul fate solution used,  
N = normality of standard sodium thiosul fate solution, and  
M = mass in g of sample taken for the test.  
 
 
 
 
 
 
 
 
 
 
 
  
4 
  
Annex B   
(Normative)  
Determination of Stability  
 
B-1 Outline of the method  
Crush the sample in a mortar and sieve. Heat it at 100 ± 2°C for 2 h and determine the available 
chlorine.  The difference in available chlorine content before and after heating is indicative of the 
stability of the  bleaching powder.  
 
B-2 Apparatus  
B-2.1 Test Tube  - About 150 mm long and 25 mm in diameter.  
B-2.2 Air Condenser  - glass tube, about 375 mm long and 5 mm in diameter.  
B-2.3 Rubber stoppers  
B-2.4 Bath  - Capable of maintaini ng at 100 ± 2°C.  
 
B-3 Procedure  
Crush the material to powder. This operation shall be carried out with the minimum delay. Fill a test 
tube to a depth of 125 mm with the sieved material and tap lightly three times. Close the mouth of the 
test-tube with the  rubber stopper carrying the air condenser so that about 12 mm of this tube projects 
below the base of the stopper into the test -tube. Place the test -tube in a bath maintained at 100 ± 
2°C for 2 h. At the end of this  period, remove the test –tube from the bath. Remove the stopper 
carrying the air condenser and close the test -tube with a solid stopper. After standing for 15 min, 
transfer the material to a glass bottle. Shake thoroughly and store.  
 
B-4 Determine the avail able chlorine on the stored material ( see A-3.2) in manner  as given in A-2. 
 
B-5 Calculation  
 
Stability =  𝑀1− 𝑀2
𝑀1 
 
 
Where,  
M1 = percent by mass of available chlorine, as determined under A-2; and  
M2 = percent by mass of available chlorine after heating, as determined under A-3.2.1 . 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
©TBS 2020 – All rights reserved                                                                                              5  
Annex C  
(Normative)  
Determination of moisture  
 
C-1 Procedure  
Weigh accurately 15 to 20 g of the sample in an open dry weighing glass, and place it for 24 hours in 
a vacuum desiccator over fused anhydrous calcium chloride under an absolute pressure of 30 to 40 
mm of  mercury. Weigh the weighing glass again. The decrease in mass corresponds to the moisture 
content of the  sample.  
 
C-2 Calculatio n 
 
Moisture content, percent by mass = 𝑀1− 𝑀2
𝑀1 
 
 
where  
M1 = mass of material taken before drying, and  
M2 = mass of material after drying.  
 
 
 
 
 
 
 
Annex D   
(Normative)  
Determination of Particle size  
 
D-1 Procedure  
Weigh accurately 50 g of the sample and place it over  1.70 mm sieve. Shake it for 15 min. The mass 
of material  passing through the sieve gives the particle  size of the sample expressed as percentage 
by mass.  
 
D-2 Calculation  
Material passing through 1.70 mm sieve, percent by mass = 𝑀1− 𝑀2
𝑀1×100 
 
Where, 
M1= mass of material taken for sieving, and  
M2= mass of material retained over the sieve.  
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
  
6 
  
Annex E  
(Normative)  
Sampling of bleaching powder  
 
E-1 General requirements of  Sampling  
E-1.1 In drawing, preparing, storing and handling test samples, the following precautions and 
directions shall be observed.  
E-1.2 Samples shall not be exposed to atmosphere for a longer time than necessary, and sampling 
shall be done as rapidly and as thoroughly as possible.  
E-1.3 Samples shall be placed in a cool and dry place.  
E-1.4 The sampling instrument shall be clean and dry when used.  
E-1.5 To draw a representative sample, the contents of each containers s elected for sampling shall 
be mixed as thoroughly as possible by rolling, shaking or stirring by suitable means.  
E-1.6 The samples shall be placed in clean, dry and air -tight glass or other suitable containers on 
which the material has no action.  
E-1.7 The sample containers shall be of such a size  that they are nearly filled by the samples.  
E-1.8 Each sample container so filled shall be sealed air -tight after filling, and marked with full details 
of sampling, the date of sampling, the month and year of manufacture of the material and its grade.  
E-1.9 Precautions shall be taken to protect the samples, the material being sampled, the sampling 
instrument and the containers for samples from adventitious contamination. Care should be taken to 
avoid direct  contact of bleaching powder with skin. Face should be kept at a safe distance from the 
container when it is  opened.  
E-1.10 Samples shall be stored in such a manner that the temperature of the material does not vary 
unduly from the normal shade temperature.  
 
E-2 Scale of sampling  
E-2.1 Lot  
All the containers in a single consignment of same grade of the material drawn from a single batch of 
manufacture shall constitute the lot. If a consignment is declared to consist of different batches of 
manufacture, the batches shall be marked separately and the groups of containers in each batch 
shall constitute separate lots.  
E-2.2 The number of containers ( n) to be selected from the lot shall depend upon the size of the lot 
(N) and shall be in accordan ce with Table 2.  
 
Table 2 Number of Containers to be Selected  
(Clause E-2.2) 
 
Lot Size  Sample Size  
(N) (n) 
(1) (2) 
2 to 8  2 
9 to 27  3 
28 to 64  4 
65 to 125  5 
126 to 216  6 
217 to 343  7 
344 to 512  8 
513 to 729  9 
730 to 1000  10 
1001 and above  11 
 
E-3.2 The material drawn from all the selected containers according to E-3.1 shall be thoroughly 
mixed together. The total material so obtained shall be divided into three approximately equal parts 
each of which shall be called a composite sample to repre sent the lot.  
 
  
©TBS 2020 – All rights reserved                                                                                              7  
 
 
FIG. 1 Galvanized Iron or plastic sampling  
Instrument  
 
 
E-3.3 Each of three composite samples obtained in E-3.2 shall be immediately transferred to 
appropriate galvanized iron containers which shall be sealed airtight immediately after filling and 
marked with necessary details for identification.  
E-3.4 One of the three composite samples shall be marked for the purchaser, another for the 
supplier, and the third kept as a referee sample.  
E-3.5 The refere nce sample shall be kept at a place and under conditions agreed to between the 
purchaser and the supplier. The referee sample shall be used in case of a dispute.  
 
E-4 Number of tests and criterion for  Conformity  
 
E-4.1 Examination and Tests  
The purchaser may examine and test separately each  of the reduced samples constituting a test 
sample for  compliance with the individual requirements or may  prepare for the purpose of such 
examination and at  every stage of the progress of the examination, a  composite sample 
represen tative of the whole lot by  mixing all the  reduced samples constituting the test  sample.  
 
E-4.2 Criterion for Conformity  
When the individual reduced samples in a test sample  are separately examined and the results vary 
from one  reduced sample to another so as to show that one or  more results are outside the limits 
prescribed in the  specification. The criteria for conformity for the quality  of the lot for the purpose of 
acceptance on the basis of  the results obtained shall be at the discretion of t he purchaser, unless 
otherwise agreed to between the  purchaser and the supplier.