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