determination of hardness of water

1. Jordan University of Science and Technology
Faculty of Engineering
Civil Engineering Department
CE 453
“Environmental lab”
“Determination Of Hardness of water”
Experiment (5)
Student Name: Anas Mohammad Maghayreh.
Student ID: 20120023117.
Section #:1
Submission Date: 26/7/2015.
Submitted to: Dr. Hani Abu Qdais

2. *Abstract:
Hardness if tendency of water not to react with soap or tendency of water
not to form a scale, which is due to the presence of divalent cat-ions mainly
Ca+2
and Mg+2
. In order to determine the hardness some indicators will be
used.
Hardness is most frequently measured through application of the principle
of chelation. Metals are capable of sharing electron pairs with a molecule or
ion to form a coordination bond. These ions or molecule called chelating
agents if it have more than one free electron pairs to share.
As the number of these bonds increase the stability of a chelate increase,
one of the most used chelating agent in analytical chemistry is ethylene
diamine tetra-acetic acid (EDTA). This chelating agent is used to find the
conc. of calcium and magnesium ions. Another chelating agent used is
metallochromic which can be used also as an indicator.
*Introduction:
Water that has high mineral content is known as Hard Water. Hard water
contains bicarbonate, chlorides and sulphates of calcium and magnesium.
When treated hard water with soap, it gets precipitated in the form of
insoluble salts of calcium and magnesium. Hardness of water is a measure of
the total concentration of the calcium and magnesium ions expressed as
calcium carbonate. There are two types of hardness:
1. Temporary hardness
2. Permanent hardness
Temporary Hardness is due to the presence of bicarbonates of calcium and
magnesium. It can be easily removed by boiling. Permanent Hardness is due
to the presence of chlorides and sulphates of calcium and magnesium. This
type of hardness cannot be removed by boiling.
in the other hand Hardness is a Water Quality Parameter, which can be defined as
the existence of Di-Valente Cations of water (Ca+2
, Mg+2
, S+2
… etc.).

3. Hardness of water is a measure of its capacity to precipitate soap, and is caused by
the presence of divalent cations of mainly Calcium and Magnesium.
Hardness EDTA as mg/L CaCO3 = (A*B*1000)/(ml of Sample)
Where: A = ml EDTA Solution Used.
B = mg CaCO3 equivalent to 1 ml EDTA Titrant.
Mg+2
Hardness as mg/L CaCO3 = Total Hardness – Ca+2
Hardness
:Objective*
To introduce the concept of complex formation and stability, and illustrate the
analytical application of these concept s to the measurement of calcium,
magnesium and total hardness in water.
*Apparatus:
1- Burette (25 ml).
2- Porcelain dish.
3- Volumetric flask.
4- Erlenmeyer flask.
5- Pipet.
6- Magnetic stirrer and rod.
Picture(1): Apparatus Requirements

4. *Sample:
Procedure:
1- Measure 25ml of a sample into a 125 ml Erlenmeyer flask.
2- Add 1-2 ml of buffer solution so PH= 10.0 ± 0.1 .
3- Add 1–2 ml of EBT indicator (used to find total hardness) .
4- Titrate the solution with EDTA till the blue color appears and record the
volume added.
5- Prepare another 25 ml sample.
6- Add 1–2 ml of sodium hydroxide buffer and 0.2g Murexide indicator (used
to find Ca+2 hardness) into the sample and add 0.1M EDTA slowly till the
color of the solution change from purple to violet and record the volume .
7- Calculate total hardness, calcium hardness and magnesium hardness
Picture (2): chemical requirements

5. Picture (3): Procedure chart

6. Results and Calculations:
HARDNESS mg/l CaCO3=A*B*1000/ml of sample where:
Total Hardness = (20* 1 *1000)/50 = 400 mg/l CaCO3
Ca+2
Hardness = (3.5 * 1 * 1000)/25 = 140mg/l CaCO3
Mg+2
Hardness = TH – Ca hard.
= 260mg/l CaCO3

7. *Discussion:
A water sample is buffered to pH 10.1 and taken in to a conical flask. If an
indicator dye like EBT, when added to a solution containing Calcium and
Magnesium ions, the color of the solution turns to wine red. EDTA, the
titrant, complexes with Magnesium and Calcium ions, removing them from
association with the indicator. When all the Mg+2
and Ca+2
are complexed
with EDTA, the indicator will turn blue. This is the end point of the titration.
In the other hand it’s easily to remove carbonate hardness by boiling while it
needs chemical reactions to remove the non-carbonates hardness
Hardness determination is based on the principle of chelation.
Murexide indicator changes in color from purple to violent and it's used to
measure the Ca+2
hardness while EBT changes in color from red-wine into
blue and it's used to measure total hardness.
Water contains relatively high concentration of and other divalent cautious is
called hard water.
The presence of Ca+2
, Mg +2
, is generally not a health threat, they can make water
unsuitable for some household uses.
Using CaO and soda ash can be used to remove permanent non- carbonate
hardness, which cannot be removed by boiling water as in carbonate hardness
(Temporary).
*Conclusion:
Hardness is the property which makes water to form an insoluble precipitate
with soap and is primarily due to the presence of calcium and magnesium
ions. Hard waters have no known adverse health effects and may be more
palatable than soft waters. Hard water is primarily of concern because it
requires more soap for effective cleaning, causes yellowing of fabrics,
toughens vegetables cooked in the water and forms scales in boilers, water
heaters, pipes and cooking utensils. The hardness of good quality water
should not exceed 250 mg/L measured as calcium carbonate equivalents.
Waters softer than 30 to 50 mg/L may be corrosive to piping depending on
pH, alkalinity and dissolved oxygen.
The major hardness in water is due to Ca², Mg² ions and other divalent ions.
Hardness of water is measure of its capacity to precipitate soap and other
industrial using.

8. The ammonia buffer which is used in the test aids in preventing precipitation
of metal ions.
Hardness caused by Ca² is higher than hardness of Mg².
As EDTA is added to solution it combines with Ca² first and then with Mg²
because the EDTA complex is more stable than the Mg² complex.
*References:
1. Lab manual
2. Lab notes
3.Wikipedia