Vishal

INDEX
1. Introduction
-Need of Water
-Purification of Water
4. Theory
-Bleaching powder and its preparation
-Use of Bleaching powder in Sterilization of
water
5. Experiment
-Aim
-Requirements
-Procedure
6. Observation Table
7. Precaution
8. Refrence
1
INTRODUCTION
Need of water
Water is an important and essential
ingredient in our quest for survival on this planet. It is very
essential for carrying out various metabolic processes in our
body and also to carry out Haemoglobin throughout the
body.
A daily average of 1 gallon per man
is sufficient for drinking and cooking purposes. A horse,
bullock, or mule drinks about 11 gallons at a time. Standing
up, an average allowance of 5 gallons should be given for a
man, and 10 gallons for a horse or a camel. An elephant
drinks 25 gallons, each mule or ox drinks 6 to 8 gallons,
each sheep or pig 6 to 8 pints. These are minimum
quantities.
One cubic foot of water = 6 gallons

(a gallon = 10 lbs.).
In order to fulfil such a huge demand

of water, it needs to be purified and supplied in a orderly
and systematic way.
But with the increasing world

population, the demand for drinking water has also
increased dramatically and therefore it is very essential to
identify resources of water from which we can use water for
drinking purposes. Many available resources of water do
not have it in drinkable form. Either the water contains
excess of Calcium or Magnesium salts or any other organic
impurity or it simply contains foreign particles
2
which make it
unfit and unsafe for Drinking
Purification of Water
There are many methods for the purification of water.

Some of them are
1. Boiling
2. Filtration
3.Bleaching powder treatment
4. SODIS (Solar Water Disinfection)
. Boiling is perhaps the most commonly used

water purification technique in use today.
While in normal households it is an efficient
technique; it cannot be used for industrial and large
scale purposes. It is because in normal households,
the water to be purified is very small in quantity and
hence the water loss due to evaporation is almost
negligible. But in Industrial or large scale purification
of water the water loss due to evaporation will be
quite high and the amount of purified water obtained
will be very less.
3
Filtration is also used for removing foreign particles
from water. One major drawback of this purification
process is that it cannot be used for removing foreign
chemicals and impurities that are miscible with
water.
SODIS or Solar Water Disinfection is recommended
by the United Nations for disinfection of water using
soft drink bottles, sunlight, and a black surface-- at
least in hot nations with regularly intense sunlight.
Water-filled transparent bottles placed in a horizontal

position atop a flat surface in strong sunlight for
around five hours will kill microbes in the water. The
process is made even more safe and effective if the
bottom half of the bottle or the surface it's lying on is
blackened, and/or the flat surface is made of plastic
or metal. It's the combination of heat and ultraviolet
light which kills the organisms. The major drawback
of this purification technique is that it cannot be used
in countries with cold weather. Also, the time
consumed for Purification process is more and it also
needs a ‘blackened’ surface, much like solar
cookers.
4
THEORY
1. A known mass of the given sample of bleaching powder
is dissolved in water to prepare a solution of known
concentration. This solution contains dissolved chlorine,
liberated by the action of bleaching powder with water.
CaOCl2+H20 → Ca(OH)2 +Cl2
2. The amount of Chlorine present in the above solution is

determined by treating a known volume of the above
solution with excess of 10% potassium iodide solution,
when equivalent amount of Iodine is liberated. The Iodine,
thus liberated is then estimated by titrating it against a
standard solution of Sodium thiosulphate, using starch
solution as indicator.
Cl2+2KI → 2KCl+I2
I2+2Na2S2O3 → Na2S4O6+2NaI
3.A known Volume of one of the given samples of water is

treated with a known volume of bleaching powder solution. The
amount of residual chlorine is determined by adding excess
potassium iodide solution and then titrating against standard
sodium thiosulphate solution.
4.From the readings in 2 and 3, the amount of chlorine and

hence bleaching powder required for the disinfection of a given
volume of the given sample of water can be calculated.
5
Bleaching powder and its
prepration :-
Bleaching powder or Calcium hypochlorite is a chemical
compound with formula Ca(ClO)2 . It is widely used for water
treatment and as a bleaching agent (bleaching powder).
This chemical is considered to be relatively stable and has
greater
available chlorine than sodium hypochlorite (liquid bleach).
It is prepared by either calcium process or sodium process.
Calcium Process
2Ca(OH )2 + 2Cl2 → Ca(ClO)2 + CaCl2 + 2H2O
Sodium Process
2Ca(OH )2 + 3Cl2 + 2NaOH → Ca(ClO)2 + CaCl2 +2H2O
+2NaCl
This chemical can be used for sterilizing water by Using 5

drops of bleach per each half gallon of water to be purified,
and allowing it to sit undisturbed for half an hour to make
it safe for drinking. Letting it sit several hours more will
help reduce the chlorine taste, as the chlorine will slowly
evaporate out. A different reference advises when using
household bleach for purification; add a single drop of
bleach per quart of water which is visibly clear, or three
drops per quart of water where the water is NOT visibly
clear.
Out of these processes, the role of Bleaching powder is

only in the last step i.e. for Disinfection of water.Then
allow the water to sit undisturbed for half an hour..
6
Process involved Disinfecting
and purification process of
water:-
The combination of following processes is used
for municipal drinking water treatment worldwide:
1.Pre-chlorination - for algae control and arresting any
biological growth
2.Aeration - along with pre-chlorination for removal of

dissolved iron and manganese
3. Coagulation - for flocculation
4.Coagulant aids also known as polyelectrolyte’s - to

improve coagulation and for thicker floc formation
5.Sedimentation - for solids separation, that is,

removal of suspended solids trapped in the floc
6. Filtration - for removal of carried over floc
7. Disinfection - for killing bacteria

Out of these processes, the role of Bleaching powder is only
in the last step i.e. for Disinfection of water.
7
EXPERIMENT
Aim:
To determine the dosage of bleaching powder
required for sterilization or disinfection of
different samples of water.
Requirements:
Burette, titration flask, 100ml graduated cylinder,
250ml measuring flask, weight box, glazed tile,
glass wool.
Bleaching Powder, Glass wool, 0.1 N
Na2S2O3 solution, 10% KI solution, different
samples of water, starch solution.
8
Procedure:
1. Preparation of bleaching powder solution. Weigh
accurately 2.5g of the given sample of bleaching powder
and transfer it to a 250ml conical flask. Add about 100-
150ml of distilled water. Stopper the flask and shake it
vigorously. The suspension thus obtained is filtered through
glass wool and the filtrate is diluted with water (in a
measuring flask) to make the volume 250ml. The solution
obtained is 1% bleaching powder solution.
2.Take 20ml of bleaching powder solution in a stoppered
conical flask and add it to 20 ml of 10% KI solution. Stopper
the flask and shake it vigorously. Titrate this solution
against 0.1N
Na 2 S 2 O 3 solution taken in the burette. When the
solution in the conical flask becomes light yellow in colour,
add about 2ml starch solution. The solution now becomes
blue in colour. Continue titrating till the blue colour just
disappears. Repeat the titration to get a set of
three concordant readings.
3.Take 100ml of the water sample in a 250ml stoppered

conical flask and add it to 10 ml of bleaching powder
solution. Then add 20ml of KI solution and stopper the flask.
Shake vigorously and titrate against 0.1N Na 2 S 2 O 3
solution using starch solution as indicator as described in
step 2.
4.Repeat the step 3 with other samples of water and record

the observations.
9
RESULT
Amount of the given sample of bleaching

powderone litre of water
required to disinfect
Sample I = … … … g
Sample II= … … … g
Sample III= … … … g
PRECAUTIONS
1.Read upper maniscus of burette
2.Cosinder accurate readings do not

go for average readings
3.Use antiparallax card
10
REFRENCE
1. TEACHERS
2. LAXMI PUB;ICATION CHEISTRY
PRACTICAL BOOK
11

Vishal

Uploaded by

Copyright:

Available Formats

Vishal

Uploaded by

Document Information

Original Description:

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Vishal

Uploaded by

Copyright:

Available Formats

INDEX

One cubic foot of water = 6 gallons

In order to fulfil such a huge demand

But with the increasing world

There are many methods for the purification of water.

. Boiling is perhaps the most commonly used

Water-filled transparent bottles placed in a horizontal

CaOCl2+H20 → Ca(OH)2 +Cl2

2. The amount of Chlorine present in the above solution is

3.A known Volume of one of the given samples of water is

4.From the readings in 2 and 3, the amount of chlorine and

This chemical can be used for sterilizing water by Using 5

Out of these processes, the role of Bleaching powder is

2.Aeration - along with pre-chlorination for removal of

3. Coagulation - for flocculation

4.Coagulant aids also known as polyelectrolyte’s - to

5.Sedimentation - for solids separation, that is,

6. Filtration - for removal of carried over floc

7. Disinfection - for killing bacteria

3.Take 100ml of the water sample in a 250ml stoppered

4.Repeat the step 3 with other samples of water and record

Amount of the given sample of bleaching

2.Cosinder accurate readings do not

3.Use antiparallax card

You might also like