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Learning The Method of Testing The Presence Of Arsenic
Arsenic measurement :1.Certain amount of sample taken
2.KI (Potassium iodide) added to the sample.
3. 1 tablespoon of Zinc compound powder added.
4. The container is shaken well.
5. Colour changes from purple to grey .
6.A Mercury strip inserted. Arsene gas reacts with Hg.
7. Reaction takes about 20 min.
8.Colour obtained can be matched with data provided.
9. The standard level is 1ppm
ANALYSIS OF WATER
Portable kit is used:
Sample: fresh water
body….(stagnant water)
pH-6.5-8.5 , conductivity-
553uS/cm,
Salinity- 0
Dissolved Oxygen- >4
Ion Selective Electrode (ISE):
Lanthanum crystal probe to test concentration of fluoride ion.
10 ml of solution containing fluoride ion taken.
10 ml Total Ionising Strength Adjustable Buffer (TISA) added.
Thus, they are in 1:1 ratio.
1.5ppm is considered within safe levels.
In west Bengal there is a high fluorite level in Baruipur , Sonarpur,
Thakurpukur areas.
Ion selective Electrode Probe for fluoride
ion detection-
•10 ml of sample is taken. Lanthanum crystal
electrode used….
• TISAB( Total Ionising Strength Adjustable
Buffer) is used
•Result- F-1 present – 0.379 mg/l
ARSENIC DETECTION
•Procedure- KI is added to sample of contaminated water- colour changes from colourless to purple.•Zn added --- changes arsenic from pentavalent to trivalent•Compound of Zinc added ----- colour changes to grey• Mercuric chloride paper held above but the solution must not touch it •If arsine gas come in contact with the paper gas turns to mercuric arsenate after 20 min black colour would be seen.
Experiment performed by the students in
the chemistry laboratory at
Geological Survey of India(GSI)
Black colouration here
indicates that the sample
contains arsenic.
Arsenic test kit
Handling the portable kit probe
Portable Kit Probe is used to
measure, H+ conductivity,
salinity, Mg and Ca ion content,
Dissolved oxygen, arsenic
content and other
properties of water sample.
For potable water D.O. is around 5.18
mg/l.
As dissolved oxygen levels in water drop
below 5.0 mg/l, aquatic life is
put under stress.
If less than 4, then water is
considered to be
stagnating.
For potable water
conductivity is less than 1000.
For potable water pH value lies between 6.5 to 8.5
Total hardness: Ca and Mg ions contribute to hardness
10 ml of sample taken.
2 drops of Eriochrome Black T
(EBT) indictor added.
NH4OH added.NH4Cl (buffer
solution) added dropwise.
The colour changes from pink to light
blue.
The value obtained is the total
hardness value.
Total Hardness
Titration Method:-
In burette EDTA is taken
•The sample is taken in dish.
•2 drops of EBT indicator is added….Buffer
is mixed……………
•Observation- colour changes from pink to
blue . Hence Mg +2 and Ca+2 are present…..
Water is an inevitable source of
life…..so being children of
mother earth we must never
destroy this vibrant heritage
of her’s.
As students, this is
the most important
approach in order to prevent
mankind from committing sins
like causing water pollution.
This a short survey that we
students had conducted….
May not be a huge one…but we have been
taught that the many little steps of ‘me’ will prove
to be the giant leap of ‘us’ ….
If we start our mission of
protecting our mother Earth
right from now…..then
future generations will be able to live
in harmony with the nature…
Thank you…
By B.D.M.International