measurement of hardness

1. Theory and measurement:
Hardness
SHROFF S.R ROTARY INSTITUTE OF CHEMICAL
TECHNOLOGY
DEPARTMENT OF ENVIRONMENTAL SCIENCE
AND TECHNOLOGY

2. Name Enrolment number Topic covered
VELIN SHAH 190990135043
MOINUDDIN SHAIKH 190990135044
TALHA SIDDIQUI 190990135045

3. What does
water
hardness
mean?
The capacity of water to precipitate soap, or the capacity of
water to form lather with soap, is known as its hardness.
Water hardness is caused by the presence of soluble
bicarbonates, chlorides, and calcium and magnesium sulphates.
Hard water is water that does not lather with soap.

4. Types of Water
Hardness
Temporary Hardness
Water becomes temporarily hard due to the
presence of magnesium and calcium carbonates.
The hardness of the water can be extracted in this
scenario by boiling it.
As we boil water, the soluble Mg(HCO3)2 salts are
reduced to insoluble Mg(OH)2, which precipitates
and is extracted. The water we get after filtration is
is soft water.
1. Temporary Hardness
2. Permanent Hardness

5. Permanent hardness
Permanent hardness is described as the presence of soluble magnesium and calcium salts in the form
of chlorides and sulphides in water, which cannot be removed by boiling.
A water softener or ion exchange resin can be used to remove ions that cause permanent hardness in
water.
Calcium Hardness + Magnesium Hardness = Total Permanent Hardness
Calcium and magnesium hardness is defined as the concentration of calcium and magnesium ions
expressed as calcium carbonate equivalents.

6. WHY IS HARDNESS DETERMINED?
Hard water isn't toxic, but it can't be used in industrial applications like
boilers and pipes. Water hardness is monitored in industrial settings to avoid
costly breakdowns in boilers, cooling towers, and other equipment. While
hardness is not generally a health hazard, it can cause serious problems.
Hard water is often indicated in domestic settings by a lack of suds when
soap is agitated in water, as well as the formation of lime scale in kettles and
water heaters. Water softening is commonly used to reduce the negative
effects of hard water wherever it is a problem.

7. Degree of
hardness
Water should have a total hardness
of less than 75 to 85 mg/l as CaCO3
and a magnesium hardness of less
than 40 mg/l as CaCO3 to minimize
scaling at elevated temperatures.
The degree of hardness consumers consider objectionable
depends on the degree of hardness to which consumers have
become accustomed, as described here:
Soft: 0 to75 mg/L as CaCO3
Moderate: 75 to 150 mg/L as CaCO3
Hard: 150 to 300 mg/L as CaCO3
Very Hard: Above 300 mg/L as CaCO3

8. How is Water
Hardness
Measured?
Water hardness is measured in "grains" per gallon,
milligrammes of calcium (Ca) per litre, or parts per
million, and German Degrees of Hardness (dH) [which
we don't include here because this is for fish tanks].
You can have the hardness of your water measured by
taking a sample to a water test lab.
You can convert between different water hardness
measurements. Water with a hardness of 25 parts per
million (ppm) contains 25 mg of hardness-causing
minerals per litre.

9. Measurement of Hardness of water
1. Estimation of the total hardness of a water sample using EDTA

10. Principle
Hardness of water is the characteristic which
prevent the formation of sufficient foam or
leather when the hard water are mixed with
soap.
Total hardness of water sample can be
determined by the titration method with
EDTA (ethylene diamine tetra acetic acid) a
chelating agent.

11. When a small amount of eurichrome black T having a blue
color is added to hard water with a pH of about 10.0, it
combined with divalent metallic ion to form a weak
complex ion which is wine red in colour as shown in
following equation.
During titration with EDTA, the EDTA heats with metallic
multivalent ion to form more stable complex in comparison
to of euro chrome black T will & thus the euro chrome
black T will free &the wine red colour of water sample will
be change to distinct blue colour as follows.
EDTA + [M.eriochrome black T] [M.EDTA]
complex+ euro chrome black T.
(Red wine colour) (More stable) (Blue colour)

12. Apparatus:
Titration apparatus. Glass wares:
Pipette, conical flask,
Measuring cylinder,
beaker.
Reagents:
• Standard EDTA solution
• Ammonium buffer
• 2N NaOH solution
• Eriochrome black T indicator

13. Procedure:
• 20ml of sample was taken in a conical flask.
• Now, 5ml of ammonia buffer solution & 2 to 3
drops of eriochrome black T (0.5g EBT powder to
make solution) was added to sample.
• The colour of mixed solution become wine red
now, solution was titrate with standard 0.01M
EDTA solution, until the colour changed from wine
red to blue.
• Reading was noted immediately.

14. Observations:
Total
hardness:
Sr.no. Location Volume of
sample in ml
Burette
reading(ml)
Volume of
EDTA used
(ml)
Total
hardness
(mg/lit) as
per CaCO3
Initial Final
1
2
3

15. Results
Results:
The total hardness of given sample is _____ mg/lit
as CaCO3.

16. Removal of
hardness
Remove Hardness of Water (Temporary)
By Boiling:
Soluble bicarbonates are converted into insoluble
carbonates which are removed by filtration.
Reactions:
Ca(HCO3)2 → ΔCalo3↓ + H2O + CO2
⇒ Mg(HCO3)2 → ΔMgCO3↓ + H2O + CO2
By Clarks Method:
Calcium hydroxide is Clark’s reagent. It removes the
hardness of water by converting bicarbonates into
carbonate.
Reaction: Ca(OH)2 + Ca(HCO3)2 → 2CaCO3↓ + 2H2O

17. How to Remove
Permanent
Hardness of
Water?
Gan’s Permutit Method:
In this method, sodium aluminum
ortho silicate known as permutit or
zeolite is used to remove the
permanent hardness of water.
Reaction: Na2 Al2 Si2 O8.KH2O + Ca++→
2Na+ + Ca Al2 Si2 O8.xH2O

18. Calgon’s
Process:
Calgon’s Process:
In this method, sodium-hexa-meta-
phosphate (NaPO3)6 known as
Calgon is used.
The hardness in water is removed
by the adsorption of Ca++ and
Mg++ ions.

19. Ion Exchange
Resin Method:
Ion Exchange Resin Method:
In this method, the permanent hardness of water is removed by
using resins. Ca++/Mg++ ions are exchanged with Cl–, SO4
-2 ions are
exchanged with anion exchange resin (RNH2OH). Demineralized
water is formed in this process.
Step 1. 2RCOOH + Ca++ → (RCOO)2Ca + 2H+
Step 2 : RNH2OH + Cl– → RNH2Cl + OH–
Step 3 : H+ + OH– → H2O

20. Harmful
Effects of Hard
Water
The following are some of the most common signs of
hard water:
Linens and clothing appear dingy and rough.
Scale build-up on faucets and unsightly stains on white
porcelain
Showers have low water pressure due to clogged pipes.
Dishes have a chalky, white residue or spots on them.
In the shower, there are strains.