With best regards,
Connecting People to Nature’, the theme for World Environment Day 2017,
Dr. AMAR NATH GIRI
EHSQ , NFCL
M.Sc. -Environmental Science,Ph.D -Environmental Science law & DIPLOMA AS - P.G.D.E.P.L,CES, DCA,
EX IIM LUCKNOW FELLOW, EX RESEARCH SCIENTIST
IGIDR-MUMBAI
9912511918
amarnathgiri@nagarjunagroup.com
http://www.nagarjunafertilizers.com
http://www.gprofonline.com/members/Default.aspx
EX IIM LUCKNOW FELLOW, EX RESEARCH SCIENTIST
IGIDR-MUMBAI
9912511918
amarnathgiri@nagarjunagroup.com
http://www.nagarjunafertilizers.com
http://www.gprofonline.com/members/Default.aspx
---------- Forwarded message ----------
From: Amar Giri <goswami248@gmail.com>
Date: Thu, Dec 24, 2015 at 10:07 PM
Subject: VERY GOOD DISCUSSION WITH JKP SIR REGARDING CHLORIDE
To: Laboratory Kakinada <laboratory@nagarjunagroup.com>
Cc: amarnathgiri <amarnathgiri@nagarjunagroup.com>
EHSQ , NFCL
M.Sc. -Environmental Science,Ph.D -Environmental Science la & DIPLOMA AS - P.G.D.E.P.L,CES, DCA,
EX IIM LUCKNOW FELLOW, EX RESEARCH SCIENTIST IGIDR-MUMBAI
9912511918
http://www.
http://dramarnathgiri.
From: Amar Giri <goswami248@gmail.com>
Date: Thu, Dec 24, 2015 at 10:07 PM
Subject: VERY GOOD DISCUSSION WITH JKP SIR REGARDING CHLORIDE
To: Laboratory Kakinada <laboratory@nagarjunagroup.com>
Cc: amarnathgiri <amarnathgiri@nagarjunagroup.com>
Dear all,
VERY GOOD DISCUSSION WITH JKP SIR REGARDING CHLORIDE
Determination of chloride in water by mohr method
December 15, 2015
Quality testdetermination of chloride in water, chloride in water, mohr method, Sources of chloride in water
Mohr method is one of the significant methods for determination of chloride in water. It is also known as Argentometric method. Chloride ion is a negatively charged ion. This method is appropriate for neutral or slightly alkaline water. Water sample is titrating against standard AgNO3 solution by using potassium chromate indicator. It is a precipitation titration method.
Determination of chloride in water
by mohr method
December 15, 2015
Quality testdetermination of chloride in water,
chloride in water, mohr method, Sources of chloride in water
Mohr method is one of the significant methods for
determination of chloride in water. It is also known as Argentometric method.
Chloride ion is a negatively charged ion. This method is appropriate for
neutral or slightly alkaline water. Water sample is titrating against standard
AgNO3 solution by using potassium chromate indicator. It is a precipitation
titration method.
Table of Contents:
• Sources
of chloride in water
• Limitation
• Theory
of determination of chloride in water
• Apparatus
• Reagents
• Procedures
• Observations
and Calculations
Sources of chloride in water
Generally, chloride ions are present in water as a
different form of salts. The most common salts are NaCl, KCl, MgCl2 and CaCl2.
They are extremely soluble in water. The Sources of chloride in water may be
natural or human beings. The natural sources are surrounding rock or soil or
seawater intrusion in coastal areas. Whereas, various human sources are
fertilizers, road salting, wastewater from industries, animal feeds, septic
tank effluents etc.
Limitation
The Mohr method for determination of chloride in water
is a pH sophisticated method. It must be perform between the pH levels 6.5-9.0.
It is better to carry out between the pH ranges 7-8. At upper pH level, the
silver ions react with hydroxide ions and precipitated as silver hydroxide. In
contrast, at lower pH level, potassium chromate may be converted into potassium
dichromate (K2Cr2O7) and mask the end point. Consequently, accurate result
cannot be obtained. If the water sample is acidic, then gravimetric method or
volhard’s method is appropriate.
Ag+(aq) + OH–(aq) → Ag(OH)(s)
CrO42-(aq) → Cr2O72-(aq)
Theory of determination of chloride in water
The amount of chloride in water can be simply
determined by titrating the collected water sample with silver nitrate solution
by using potassium chromate indicator. The reaction is quantitative. The AgNO3
reacts with chloride ion in a 1:1 ratio. The result is expressed as ppm.
When silver nitrate solution is gradually added into
the flask, then silver ions react with chloride ions and forms silver chloride.
It is precipitated in bottom of the flask. The precipitation is white in color.
Ag+(aq) + Cl–(aq) → AgCl(s)
The end point of the titration takes place when all
the chloride ions reacts and precipitated. Then slightly extra silver ions
react with the chromate ions and form a brownish-red precipitate of silver
chromate. The solubility product of silver chromate exceeded in the presence of
additional silver ions, and then the precipitation occurs.
2Ag+<sub(aq)< sub=""> + CrO42-(aq)
→ Ag2CrO4(s)
Apparatus:
Conical flask, burette with stand,
pipette, measuring cylinder, volumetric flask, beakers, wash bottle.
Reagents:
Deionized water, water sample,
standard N/50 silver nitrate solution, pH test paper, sodium hydroxide
solution, nitric acid, Indicator potassium chromate solution.
Procedures:
1. Measure
the pH of the water sample. Adjust the pH with nitric acid or sodium hydroxide,
if needed.
2. Take
a 25 ml collected water sample into a conical flask.
3. Add
2-3 drops potassium chromate (K2CrO4) indicator. The color of the water sample
is turn into light yellow.
4. Add
standard N/50 silver nitrate solution from the burette and shake well. Titrate
until the light yellow color changes to permanent brownish-red color
(bricks-red color) precipitate with white color precipitate.
5. Note
the volume of silver nitrate added.
6. Repeat
the titration for concordant values.
7. Calculate
chloride ion concentration
Chloride ion concentration (mg/l) =
(VSN× NSN ×35.45) ×1000/Vw
Where: VSN = volume of titrant used,
NSN is normality of silver nitrate, and Vw = volume of water sample used (ml)
NB: If the collected water contains
massive amount of Chloride ions such as sea water. Then it needs to be dilute
into a volumetric flask.
Observations and Calculations:
|
Serial No
|
Volume of collected water sample (ml)
|
Burette readings (ml)
|
Volume of silver nitrate solution (ml)
|
|
|
Initial
|
Final
|
|||
|
1
|
||||
|
2
|
||||
|
3
|
||||
Concordant Volume of silver nitrate
solution, VSN = …. ml
Normality of standard silver nitrate
solution, NSN = 0.02N
Volume of silver nitrate solution,
VSN = ……… ml
Volume of collected water sample, Vw
= ……. ml
Normality of collected water sample,
Nw = ?
Now, Nw can be calculated from the
following normality formula
Nw ×Vw = NSN × VSN
Or, Nw = NSN × VSN / Vw
Amount of Chloride ions = Nw ×
equivalent weight of chlorine
= Nw × 35.45 g/lit
= Nw × 35.45 × 1000 mg/lit or ppm
Result: The Amount of Chloride in
water sample is ——- ppm
eting against standard AgNO3 solution by using potassium
chromate indicator. It is a precipitation titration meto.
With best regards,
"Seven Billion Dreams. One Planet. Consume with Care."
(2015)
Dr. AMAR NATH GIRI"Seven Billion Dreams. One Planet. Consume with Care."
(2015)
M.Sc. -Environmental Science,Ph.D -Environmental Science la & DIPLOMA AS - P.G.D.E.P.L,CES, DCA,
EX IIM LUCKNOW FELLOW, EX RESEARCH SCIENTIST IGIDR-MUMBAI
9912511918
http://www.
http://dramarnathgiri.
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