This document discusses determining the alkalinity of a water sample through titration with dilute sulfuric acid using phenolphthalein and methyl orange indicators. Alkalinity is a measure of a water's capacity to neutralize acids and is primarily due to carbonate, bicarbonate, and hydroxide ions. The procedure involves adding sodium carbonate and an indicator to a water sample, then titrating with acid and recording the endpoint color changes to calculate alkalinity concentration.

1. Determination of Alkalinity in Water
Aim
To determine acid neutralizing capacity of given water sample.
Theory
INTRODUCTION
Alkalinity is the presence of sufficient alkaline ions in water. The absence of
alkalinity makes the water acidic. Water is said to be alkaline when pH of water is above
7.00. The determination of alkalinity is very useful in water and waste water because it
provides buffering to resist changes in pH value. The alkalinity and acidity in water
usually changes in natural waters with large algal growth. The alkalinity of natural
waters is primarily due to the salts of week acids and bicarbonates represent the major
form of alkalinity. Alkalinity can be expressed as follows:
Alkalinity (mol/l) = [HCO3
-
] + 2[CO3
2-
] + [OH-
] – [H+
]
The presence of alkalinity in surface waters is primarily indicates the
concentration of carbonate, bicarbonate and hydroxide contents. Alkalinity in excess
of Alkaline earth metal concentrations is significant in determining the suitability of a
water for irrigation. Alkalinity measurements are used in the interpretation and control
of water and waste water treatment processes. Raw domestic waste water has an
alkalinity less than or only slightly greater than that of the water supply.
Alkalinity of water is the capacity of water to neutralize acid. It is usually
expressed as Total Alkalinity or Caustic Alkalinity in water. It is significant in many uses
and treatments of natural waters and wastewaters. Alkalinity is measured titrimetrically
by titrating against Dilute Sulphuric Acid. Phenolphthalein and Methyl Orange are used
as indicator to indicate pH 8.3 and pH 4.3. Phenolphthalein process a pink colour when
pH is above 8.3 and colourless when pH is below 8.3.
Relevant Indian Standard for Alkalinity Test :
1. IS 3025-23 (Part 23) - 1986: Methods of Sampling and Test (physical and chemical)
for Water and Wastewater, Alkalinity, First Revision.

2. Procedure
These procedure steps will be followed on the simulator
1. Open the simulation of alkalinity of water and click on the arrow mark shown
at the bottom right corner.
2. Click on the funnel to place it on the burette.

3. 3. Click on the lid to open and click on the bottle to pour dilute sulphuric acid on
to the burette up to zero mark.
4. Remove the funnel by clicking on it. Click on the NEXT button once the funnel
is removed.

4. 5. Squeeze the pipette bulb by clicking on it and press the up arrow to take the
Na2CO3 solution up into the pipette.
6. Press the down arrow on the pipette bulb to release liquid into the conical
flask.

5. 7. Note the addition of 10ml 0.02N Sodium carbonate solution to conical flask.
Click on NEXT button.
8. Click on the dropper to add methyl orange indicator to the conical flask.

6. 9. After the addition observe the change in colour of the solution, then click on
the NEXT button.
10. Click on the knob to add the dilute sulphuric acid into the conical flask.

7. 11. Observe the colour change of the solution in the conical flask to wine red.
Click on the NEXT button.
12. Calculate Normality of Sulphuric acid using the formula and enter the value
then click on CHECK button to check the result.
13. Repeat the same procedure for the 100ml of water sample and note down the
observation. Calculate the alkalinity of water using the formula and enter the

8. value then click on CHECK to check the result.
http://vlabs.iitb.ac.in/vlabs-
dev/labs/nitk_labs/Environmental_Engineering_1/experiments/determination-of-alkalinity-
nitk/simulation.html
References
1. IS 3025-23 (Part 23) - 1986: Methods of Sampling and Test (physical and
chemical) for Water and Wastewater, Alkalinity, First Revision.
2. AWWA, WEF, APHA, 1998, Standard Methods for the Examination of Water
and Wastewater (Method: 5210B,5-day BOD).
3. Sawyer, C.N., McCarty, P.L., and Parkin, G.F. 2000. Chemistry for Environmental
Engineering 4th Edition. Tata McGraw-Hill Publishing Company Limited.

9. Pre Test
Permissible limit of alkalinity in drinking water is
a : 50mg/l b : 300mg/l c : 20-200mg/l d : 100mg/l
Alkalinity in waste water is useful because it provides buffering to resist changes in
pH value.
a : True b : False
Alkalinity can also be related to hardness because of presence of
a : CaCO3 b : MgCO3 c : Na2CO3 d : K2CO3
Alkalinity is important in aquatic life because
a : It helps water to remain warm b : It helps water to remain cold c : It buffers
against rapid pH change d : None of the above
An alkalinity test measures the level of
a : Carbonates only b : Hydroxides only c : Bicarbonates, carbonates, and
hydroxides d : None of the above
Post Test
Higher is the alkalinity in water easier it is for pH change.
a : False b : True
Excessive alkalinity level in human body can
a : Expel the unwanted pathogens in the bloodstream b : Cause skin irritations
c : Lead to gastrointestinal issues d : All of the above
Data obtained from alkalinity is used for following engineering practices.
a : Chemical coagulation of water and waste water b : Water softening c :
Corrosion control d : All of the above
Majority of mineral water supplied is mostly

10. a : Acidic b : Neutral c : Alkaline d : None of the above
Alkalinity measurements are used in the interpretation and control of waste water
treatment process.
a : False b : True