Determination of Total, Permanent and Temporary Hardness of Water

Author: Farhan Khan
Posted On: July 5, 2020
Updated On: July 5, 2020

Table of Contents

Introduction:

Water is a vital source of life for all the living organisms in the world of all species. It is a combination of right proportion of oxygen and hydrogen in it. This property of hardness may rise due to the inadequacy of the salts dissolved in the water naturally.

The most important part of having anything at its best is its proper defined proportion. This abnormality of composition may result into its adverse effects on use for drinking, cooking, bathing, or any kind of consumption whether its human or marine.

This is the very reason why marine life is highly affected usually because of the variating compositions along with the plant life is highly affected by not meeting the right amount of nutrients. The hardness of water may result into various infections or problems.

Related theory:

The first definition to be listed here is about the hardness of water defined as:

“Hardness of water is that quality which has an increased concentration of salts resulting into the formation of a substantial quantity of soap formation along with a quality of scaling the surroundings of it such as water pipes, geysers, boilers, heaters etc. dealing with the increase of the temperature.”

It has harmful affects resulting while interacted with soap therefore it uses is usually avoided and the soap removal is preferred. This quality is variant depending upon the atmosphere and all other quantities. Their classification can be studied as under.

Hardness (mg/L)	Degree of hardness
0-75	Soft
75-100	Moderately hard
150-100	Hard
>300	Very hard

Hardness is defined as the result of the cations formed I.e. polyvalent metallic. The hardness is no doubt majorly the result of increased calcium and magnesium concentration in terms of carbonates usually in mg/L. this is equal to the alkalinity causing it termed as carbonate hardness also when alkalinity is hardness of carbonates representing the major cause of it.

The increased composition of other solids such as nitrate ions or sulphate chlorides turn the water into the state of non-carbonated hardness associated with its components. It is the exclusion of the hardness of carbonate from the total hardness of it.

It is determined in terms of mg/L by two techniques explained as under:

a)Method of Calculations

The hardness of water is determined mathematically through calculations as follows:

The equation concentration of the cations is to be already known being shown in terms of CaCO₃ . The following is adopted for its determination:

Hardness = [M²⁺ * 50]/(Equivalent weight of M²⁺ions)

Where,

M²⁺is the amount of the divalent ions (mg/L)

b)Method of EDTA titrimetric determinations:

The use of the ethylene diamine tetra-acetic acid and the chelating agents developing the calcium and magnesium ions along with other ions of divalent frequencies causing the water hardness.

Its use is entirely dependent on the indicator showing the EDTA solution being in excess along with the presence of all other ions in the solution. The addition of a small amount of EBT in a hard water results into the combining of the calcium and magnesium ions resulting into the formation of a weak complex ion.

The titration process with the EDTA all the hardness forming ions result into the complex ions finishing the wine-red color resulting on the basis of stable complex ions resulting into blue color when the titration process is completed.

Apparatus:

The following apparatus are included in the test:

A burette
A pipette
A bottle
An Erlenmeyer flask
An EBT
An EDTA (sample of 0.01M)

Procedure:

The following procedure is adopted:

A 25 mL of sample is adopted and being diluted to 50 mL by using distilled water in the flask (Erlenmeyer).
A buffer solution is now added usually 1mL is adopted.
An indicator is now added i.e. 2 drops in the solution which turns it into a wine red color.
The titration is then carried through EDTA along with the constant mixing until the color is completely transformed from wine red to blue normally at standard conditions.
The volume is now determined against the complete titration.

Observations:

Sample #.	Trial #.	Sample Volume (mL)	Burette Reading		EDTA Volume (mL)
Sample #.	Trial #.	Sample Volume (mL)	Initial	Final	EDTA Volume (mL)
1.	——–	——–	——–	——–	——–
	——–	——–	——–	——–	——–
	——–	——–	——–	——–	——–
2.	——–	——–	——–	——–	——–
	——–	——–	——–	——–	——–
	——–	——–	——–	——–	——–
3.	——–	——–	——–	——–	——–
	——–	——–	——–	——–	——–
	——–	——–	——–	——–	——–

Calculations:

The following calculation are adopted:

Hardness(mg/L)= (EDTA Volume S 1000)/V

Where,

S is the quantity of CaCO₃ equal to 1mL of the titrant adopted.

V is the total volume of the sample.

Hardness(mg/L)= (EDTA Volume 1000)/V

Sample description	Hardness (total in mg/L)
1.	——–
2.	——–
3.	——–

The result is determined as an average usually.

Comments:

The comments are made on the samples hardness along with its capacity and the hardness by keeping in account the standards adopted whether it is permanent or temporary.

Precautions:

The following precautions are to be adopted:

The calibration of the burette is to be read carefully.
The sample is to be properly diluted against equivalent amounts.
Titration is to be carried out under proper care.
The instruments must be cleaned thoroughly.

Author: Farhan Khan

Farhan is a highly experienced civil engineer from the Southern side of Texas and has been associated with ConstructionHow since 2020. Over almost a decade, his wide span of expertise enabled him to bring forth his fair share of stories and experiences related to the most iconic engineering examples worldwide. He has also contributed to online and offline publications on requests. Engineering is his passion, which is why he chose to become part of our honorable team of industry experts looking to provide authentic and credible guidelines to the reader.