Water is the commonest substance on the earth, which covers about 70% of the planet. All living organisms consist mostly water. Earth, air, fire and water were considered by some ancient philosophers to be four chemical substances, a concept that progresses through the middle age. Water is a colourless, clear liquid usually with boiling (100°C / 212°F) and freezing point (0°C / 3 2°F). These discrepancies result from the strong attraction that each water molecules has for others, so that the energy required to meet the solid and boil the liquid is greater than could be predicted. Water also shows unusual volume change with increasing temperature. As warm water cools, it contracts until its reach it maximum density at 4°C (39°F). Further cooling effects on expansion of the liquid phase, and another expansion occurs when the liquid freezes to form ice. Both of these peculiarities occur because of the formation of highly ordered arrangements of hydrogen bonding of the water molecules. Pure water is a poor conductor, but the impurities found in natural water helps it in its dielectric constant and as a universal solvent. According to the comments by Wood Ward 1966), “some water are indeed so very clear and transpired that would not easily suspect any terrestrial matter were latent in them, but these may be of highly saturated with such matter.

  1. 1 Types of Water

Natural Water:

Natural water includes rain water, lake water and sea water. Rain water is the purest form of natural water because it is formed as a result of the condensation of water vapour in the atmosphere, that is, it is a natural form of distilled water. Spring water contains a considerable amount of mineral salts but very little suspended impurities such as dust and bacteria. So it is a good source of drinking water. Well water contains a lot of clay and other minerals salts. Axell that is used as a source of drinking water should be:

  • Sited away from sources of underground water pollution such as pit latrines.
  • Lined with bricks and covered. Water from deep wells; tend to be less polluted than that from surface well. Generally it is safer to boil well water before drinking. River water, lake water and sea water contain a lot of dissolved air, mineral salts, bacteria and organic remains.

Treated Water:

Treated water is usually prepared for special purposes. Examples of treated water are distilled water, pipe borne water, and chlorinated water for use in swimming pools.

Treated water is obtained from the treatment of the impure or the natural water in some forms, it depending on the types of impurities present and the purpose to which the water is needed for use.

Distilled Water:

This is the purest of all form of water. It is obtainable in the laboratory where it is commonly used for the dissolution of substance when undertaking quantitative analysis. Distilled water is obtained from the condensation of water vapour or stream through the process called DISTILATION. Thus, distilled water is free of all solute substances. It is suitable for use in all purpose, but does not give much pleasure when taken as drinking water due to its tastelessness.

Pipe-borne Water:

This is another form of treated water and it prepared by filtration and treatment of the natural or the impure water with chemicals to coagulate solid impurities and to kill the bacteria and all forms of germs in it. However, pipe- borne water contains some mineral solute such as Sodium chloride, which are highly essential to the body. Thus pipe-borne water is the most suitable form of water for all sorts of domestic purpose, since it is free from germs and disease vectors that could transmit ailments into human body.

Chlorinated Water:

Chlorinated water is treated with chlorine or other germicides primarily to kill germs of infection diseases such as diseases of the skin, tuberculosis, liver fluke etc. which might have been introduced into it by carrier of such diseases.

1.2 Characteristics of Water

The true picture of the nature of a particular sample of water can be gained by measuring several different properties through analysis under the broad headings of physical and chemical characteristics.

Physical Characteristics

Physical properties are in many cases relatively easy to measure and some may be readily observable by a lay man.

(i) Taste and Odour: Pure water is tasteless, but this is hardly obtainable in nature because of the dissolved impurities of ten organic in nature e.g. phenol and chlorophenol. They are subjective properties, which are difficult to measure.

(ii) Colour: Pure water is colourless, natural yellow colour in water from upland cantonment is due to organic acids which not in any way harmful, being similar to tranic acid from tea.

(iii) Turbidity: Water that is not turbid is hardly got In nature. The presence of colloidal solids e.g. clay, slit, particles and micro-organisms give liquid a cloudy appearance which is aesthetically unattractive and may be harmful.

(iv) Electric Conductivity: The conductivity of a solution depends on the quantity of dissolved salts present. Other physical properties, which may sometimes be important, are:

(v) Radioactivity

(vi) Density (g/dm3) at 4°C.

(vii) Viscosity

(viii) High dielectric constant

(ix) Melting point of 0°C.

(x) Neutral to litmus papers.

Chemical Properties

The chemical characteristics of water are:

(i) pH: The intensity of acidity and alkalinity of sample is measured on the pH scale which actually measures the concentration of hydrogen ions present. Water is weakly ionized.

Many chemical reactions, (H20 à H+ 0H) are controlled by pH and biological activity is usually restricted to a fairly narrow pH range of 6 — 8. Highly acidic or highly alkaline waters are undesirable because of corrosion hazards and possible difficulties in treatment.

(ii) Oxidation — Reduction Potential (ORP): In any system undergoing oxidation, there is a continual change in the ratio between the materials in the form and those in the oxidized form.

(iii) Alkalinity: Due to the presence of HCO3, CO3 or OH, most of the natural alkalinity in water is due to bicarbonate (HCO3) produced by the action of ground water in limestone or chalk in the presence of carbon dioxide (C02)

CaCO3 + H20 + CO2 à Ca(HCO3)2

The amount of alkalinity present is expressed in terms of CaCO3.

(iv) Acidity: Most of the natural acidity in water is due to the presence of CO2. Acidity is also express in terms of CaCO3.

(v) Hardness: This is the property of water which prevents lather formation with soap and produces scale in hot water system. It is due mainly to the metallic ion Ca2 and Mg2. There is no health hazard but economic disadvantages of hard water include increased soap consumption and higher fuel costs. Hardness is expressed in term of CaCO3 as well.

(vi) Dissolved Gases: Gases such as chlorine, oxygen, nitrogen and carbon dioxide from the atmosphere dissolved in water, and the most important of them all in water quality control is oxygen.

1.3 Hardness of Water

Hard water will not form lather readily with soap. It contains a number of dissolved salt, the most important being Calcium tetra-oxosuiphate (VI), Magnessium tetra-oxosuiphate (VI) and Calcium hydrogen trioxocarbonate (IV). Soap is the Sodium or Potassium salt of an organic acid (Fatty acid), ordinary soap is usually sodium octadecanoated origin of hard water. Water acquired hardness when it dissolves gypsum, (CaCO4.2H20) or limestone (CaCO3) from soil over which it flows. Gypsum is sparing soluble in water which contains carbon (IV) oxides, is capable of dissolving small quantities of limestone. The reaction is as follows:

CaCO3 + C02(g) + H20 Ca(HCO3)2(aq)

(Insoluble) (Soluble)





Water occurs abundantly in nature as water vapour in the atmosphere, as

liquid water or ice in the ocean and in land waters, as water of hydration in many rocks and minerals in the earth crust.

1 Natural Water

The purest form of natural water is rain water, in country districts rain water contains in solution oxygen, Nitrogen and carbon dioxide absorbed from the atmosphere and Ammonium nitrate formed by electrical discharges during thunder storms. Rain water failing over towns is liable to contain also oxides of sulphur formed from the burning of sulphur, ferrous coal, as well as soil and dust particles.

Rain water falls on the ground and percolates through the soil, dissolving rocks soluble in pure water, and those chemically attached by a dilute solution of carbon dioxide.

The nature of impurities in spring well or river water must therefore depend on the nature of the rocks with which the water has been in control, this water frequently contain the chlorides, sulphates, bicarbonates and carbonates of sodium, calcium, magnesium and iron, salt of potassium are present less frequently because they are preferentially retained by the soil.

Research has shown that lakes are the sources of most impure water with almost 3.6% of solid matters, and sometimes too, it might be higher. The same research has equally shown that the most pure or least impure form of water is the rain water from the country districts.

It contains about 0.0005% of solid impurity. The earth surface has been

estimated to be 70% water rich and 30% water free.

The relative amount of water in circulation in the world is fairly constant. However, it is sometimes in another use for instance when in circulation. This circulation of water tends to form gigantic water cycle and it is permanent operation. The largest collections of natural water are in the seas, lakes, rivers and oceans. These are directly exposed to the atmosphere and allow evaporation to take place.

2.2 Evaporation

This is the movement of water molecules into the atmosphere; it is a physical process and can occur at any temperature under ordinary conditions, evaporation takes place always and especially on dry sunny day. The water apour that gives into the atmosphere gets condensed. The condensed water vapour becomes water droplets floats in the air as cloud messes and the accumulated water falls as rain drop. Also the rain drops are equally prone to evaporation as soon as it reaches the earth surface. Therefore, the process of rain dropping is a continuous one, even though it has been indicated that not all the raindrops are evaporated, while some are evaporated, some goes down into the soil for plants consumption and some gather up bigger into the soil they are subject to being found in the wells. The process behind in this case takes place down beneath the soil. Some will be absorbed by plants which are equally posted to the air through the stomata and lenticels. But those which are consumed by the ammals are released in sweats during excretion or excreted as unne.

The hardness of water depends on many factors even though the source of

water depends on some factors. An example where a river bed is of impervious materials like granite, the water may be fairly pure. But in limestone areas, the river tends to be more harder because the dissolved calcium hydrogen trioxocarbonate (IV) which is contained in it. Also, it is not good for human consumption unless it is been treated with chemical unlike the river water, tap water contains less impurities and it has been already subject to chemical treatment which makes it more consumable. Apart from the natural causes of hard water, these are also some consequential causes e.g. streams could be polluted by organic waster in the cities farms, industries and firms. The water waste in the cities fanns, industries and firms. Human being can easily contract some infections, diseases by consuming dirty water, such as dysentery, typhoid, and cholera, if it is not treated with chemical. The importance of water as a solution cannot be down-looked. The air we breathe and the water we drink are solutions. The food we eat is firstly digested and then dissolved in the blood before transport to other various parts of the body; it is used to produce energy. Carbon dioxide in the air is dissolved in water in the leaves of green plants; it will be used to produce oxygen and build tissues. Oxygen which dissolved in water is always used by the aquatic organism for respiration. Carbon dioxide is produced and the carbon dioxide produced will dissolve in water and it is used by water plants to produce oxygen through respiration.

The rain dissolves gaseous impurities from the atmosphere and will help freshen the air we breathe. The quality of the water substances dissolved from the rock, through which underground water and run off from feed and seriously fertilized farm land pollutes air, river, with hundred of dissolved substances that must be removed, without proper understanding of the properties of solution we cannot understand these and related environmental problem.

2.3 Electrical Conductivity

in a completed electric circuit, where water is the electrolyte, the lamp glows, therefore electricity is being conducted from one electrode to the other through the solution. A solution that can conduct electricity is called electrolytes. Infact therefore, solution that do not conduct electricity are termed non- electrolytes. Tap water is a good electrolyte and some one must be careful when handling electrical equipment in its presence. However, water is a weak electrolytes, a weak electrolyte do not dissociate completely when in solution.

For example, H20 > H + 01-F, in weak electrolyte, one do realizes that there would still be hydrogen ion on both element dissociating. To buttress this is the dissociation of ethanoic acid, CH3COOH > CH300 + W, this is a weak electrolyte.

2.4 Sources of Water

The following are the natural forms and occurrences of water in earth’s


(i) River water

(II) Rain water

(iii) Well water

(iv) Lakes and seas (oceans)

(v) Spring water.

River Water: Rivers are formed naturally when spring or similar running water come together and eventually flows along the same rate. It contains dissolved particles as well as mineral particles. The minerals particles depend so much on the river bed.

Where the river bed for instance is of impervious large, the impurities dissolved will be fair, but if the river bed is limestone, the water will be hard water. This is because Calcium hydrogen trioxo-carbonate (IV), Ca(HCO3)2 will be dissolved, so also bacteria into the river water. Hence, it is very much unsuitable for drinking otherwise treated with chemicals or boiled.

Rain Water: Rain water is the purest form of natural water. This is because it is formed as a result of evaporation and consequent of the water droplets. Hence, this is a believed to have been naturally distilled. It contain about 0.0005% when collected in the country districts. However, because it is water, and of course water is a universal solvent, one may not deny that it can dissolve some gases in air. To buttress this is the fact that it dissolved nitrogen, Carbon (IV) oxide, oxygen, dust, air born bacteria but still depends on conditions. It is usually soft and hence lathers easily with soap.

Well Water: This is a man-made source of water. The water is under the surface. Hole are dug to approach the water length of each well depends on the nature and type of the earth at the particular points. Hence a function whether the place is rocky or water logged. Well is a stagnant one and may contain remains of the dead organisms over the ages of long decades.

It’s usually contains clay and therefore not recommended for man consumption unless treated with alum or boiled.

Lakes and Seas: These are from reservoirs, river and running water. They are the reservoirs into which all the impurities eventually go and hence, the solid content of the sea water is usually high about (3.6°/o impurities). The solids which are found in the natural water are mainly the suiphates and bicarbonates hydrogen carbonates) of calcium magnesium together, with smallest amount of sodium chloride, silicate, nitrate, ammonium salts as well as the gaseous impurities already mentioned are present in rain water. i.e. Oxygen (02), Nitrogen (N2) and Carbon (IV) oxide (C02).

The percentage of solid matter here is usually veiy high due to the calcium sulphate and calcium bicarbonate (hydrogen carbonate). Generally the impurities which maybe present in water may be grouped into classes.

(i) Matter in solution

(ii) Matter in suspension.

Each of these classes may be sub-divided into (a) inorganic or (b)

mineral matter.

Organic matter consists of bacteria sewage and other forms of animal and

vegetable mater in various stages of decay. There are also some micro-organism found in natural water. Water which seep through the ground or runs off as surface water into streams becomes exposed to many kinds of decaying organic matter and micro-organism, such micro-organisms include algae, fungi, harmless bacteria and diseases germs, all these may contaminate the water, some of these may discolour the water and impacting an unpleasant taste or colour. Streams become polluted from the organic waste materials of cities and farms, such surface water may become contaminated by water seeping into it. Typhoid and paratyphoid, dysentery, cholera and other intestinal diseases may result from the consumption of such water if is not purified (lyons and Carnalan, 1952).

Spring Water: When it rains, some of the water enters into the porous layer by percolation, until it collects above the impervious layer. Excess of this water may emerge again on the soil surface as spring water. During its percolation through the various layers, it dissolves on a considerable amount of minerals water.

Spring water of course contains solid impurities and suspended impurities in it such as dust and bacteria and they may be filtered off, spring water is therefore a good source of drinking water.

2.5 importance of Water

The aqueous origin in life justifies the essentiality of water as life’s primary source. Water is an essential source of life in that; it constitutes a reasonable percentage of the content of plants and animal cells (between 60% and 800/o).

Plants and animal depend largely upon water for their daily survival. Water plays vital roles in the body cells of plant and animal. It is required as a solvent for biological reactions and for transporting substance across the membranes of plants and animal body cells, maintaining body temperature, producing digestive fluid and dissolving waste products for excretion. Inadequate availability of water to plants leads to a resultant wilting and eventual death of plants.

In man, insufficient water in the body due to dehydration or otherwise may results to severe diarrhea, vomiting, fever or unusually high body temperature which may be very chronic in children, It is however imperative to note that too much of water intake could also cause a disease called EDEMA which is often observed in children suffering from kwashiorkor.

Domestically, we use water for many purposes. We use water for drinking and laundry purpose such as: drinking, cooking our foods, washing our cloths and utensils and for bathing, pure water is free from germs and diseases in order to enhance a perfect healthy life existence.

Distilled water is found useful in hospitals in preserved forms which drive into the body cells of sick patient to ameliorate the death of the amount of water in the cells. Also water has been found useful as drug to cure many ailments such as fever, tuberculosis and many others. It was prescribed intervals is capable of curing any of this body ailment (LUTH).

Water is highly useful in some firms and industries where drying machines are use. An example of such firms or industries is the wood industries, where water is strongly heated in the boiling section to supply steam to drying their semi-finished and finished products. Water because of its solvents properties, it is found useful in science laboratories to cany out qualitative test.

2.6 Purification of Water

The need for water treatment or purification arose to the vast uses in which water is being employed. The use of water as a solvent could be found useful in science laboratories for qualities experiment.

Hard water is not suitable for domestic and laundry purpose except it is treated and the hardness removed. The natural water, especially the river, ocean, lakes and sea which are harmful to health, if not removed from water used for domestic and laundiy purposes.

Impurities in water makes the definite properties of water unascertamed, this consequently result to ambiguous observation and possible wrong interferences which do not give reliable conclusion of results obtained during the use of such contaminated waters for laboratory qualitative experiments. These hazards cause by the qualitative experiments. These hazards cause by the impurities in water, brings about the need for water purification.

Types of Purifications of Water

There are various ways in which water can be treated or purified. This largely depends on the type of impurities in water we wanted to remove and the use we wanted to employ of water. We have the distillation and the chemical treatment methods of purification of water.

Distillation: Distillation is a standard laboratory method of water purification to the production of pure water called DISTILLED WATER used for quantitative analysis. It is prepared by condensing water vapour or steam and its thus free from all solutes and is soft and forms lather with soap, easily. Distilled water is useful in Distilleries where it is further treated and preserved for use in hospitals for patients that are short of water in the body. Distilled water as a form of pure water could be used as drugs to cure many ailments such as skin diseases, fever, tuberculosis e.t.c. which are health hazards.

Distilled water from the distillation process is known to be the purest form

of liquid water, but it is some what strenuous and costly in obtained. It may also required subsequent re-distillation of the initial distillate.

Boiling of Water

Some form of water which contains simple impurities (such as in temporary hard water) can be purified by mere boiling. Boiling kills some of the germs, which might be present in this waters and also coagulate solid impurities including the hydrogen tri-oxocarbonate (IV) of calcium and magnesium which causes temporary hardness of water. Boiling of water is difficult to employ in case of large volume of water, it takes a long time for hydrogen and oxygen ions in water molecules to orient themselves. Therefore, boiling is not an effective method of water.

It is realistic that water acquires hardness when it dissolves gypsum (CaSO4.2H20) or limestone (CaCO3) from the soil over which it flows. Gypsum is then sparingly soluble in water but that of limestone cannot do so. However, water which contains carbon (IV) oxide is capable to dissolve small quantities of limestone. Hard water can also form carbonic acid due to the reactions of carbon dioxide with water. The process that makes the reaction to take place in the hardness of water is by the microscopic marine which at ordinary environment pH exist mostly as bicarbonate ion. Ground water made slightly acidic by CO2 from the air and from the respiration of soap bacteria which dissolve the limestone, thereby it acquiring calcium and bicarbonate ions and becoming “hard”.

If the HC03 concentration is sufficiently great, the combination of processes and the causes of carbonate which is “lime scale” is to precipitate out on the surface such as inside of the pipe (calcium bicarbonate itself does not form a solid, but always precipitates as CaCO3).

Ordinary water is impure; it usually contains dissolved salts and dissolved

gases, and sometimes organic matter. Hard water containing cations of calcium magnesium and iron which are undesirable because they form a precipitate with

ordinary soap and react with other substances.

Hardness ions: This is the process by which the three divalent cations present in water, including calcium (Ca2), magnesium (Mg2) and ferrous (Fe2). Hardness ions develop from dissolved minerals, bicarbonate, carbonate, sulphate abd chloride. Bicarbonate salt cause temporary hardness, which can be removed by boiling the water and leaving behind a calcium carbonate solid. Calcium hardness can be removed by adding excess sodium carbonate to precipitate Ca2 as CaCO3. Hard water can be passed through an exchange column where hardness ions are captured on the resin. Removal of hardness is the process called water softening. More seriously, the calcium and magnesium carbonates tends to precipitates out as adherent solids on the surfaces of the pipes especially on the hot of heat exchanger surface of boilers. The resulting scale building can then flow of heat into the water. It is not only residues heating efficiency but allows the metals or ions to over heat after it has been pressurized, the systems can now become catastrophic failure.

Hard water, as process implies in a substance which will not form lather readily with soap. It contains a number of dissolved salts, the most important being calcium tetraoxosulphate (VI), magnesium letraoxosulphate (VI), and calcium hydrogen trioxocarbonate (IV).

Soap is the sodium or potassium salt of an organic acid. An ordinary soap

is usually sodium octadecanoate. When soap is added to hard water, the dissolved salt in the water will immediately reacts with the soap, molecules.

The insoluble calcium and magnesium salt form an unpleasant scum which is wasteful, as a large amount of soap has to be used in precipitating and removing the calcium and magnesium ions; after which more soap has used in the actual washing.

In recent years, this problem has been overcome by the introduction of detergents for domestic and laundry purposes. These detergents is for domestic used because of the formation of calcium and magnesium salts to affect by hard water and soluble in water. When water is agitated with soap, lather is produced. Sodium stearate is a typical soap. Water derived from natural resources such as rivers and wells usually contains dissolved solids; these dissolved solids are the hydrogen carbonate (HCO3) and sulphate ion (S042) of calcium ions and magnesium. Calcium and magnesium stearate are both soluble in water so that they precipitate out as a curdy scum. One of the reactions that wastes soap in the solution for cleansing and produce dirty scum is:

Ca2 + 2C17H35C00 > (C17H35COO)2Ca2

Hard water is due to metal (minerals) that are dissolved in the water. These minerals include Ca2, Mg2, Fe2, S042 and HC03. 1-lard water is due to rain moving through the vast amount of limestone, CaCO3 that occurs in our area to the aquifer. This is why we measure hardness in terms of CaCO3 the concentration of any other ion in the water.

Hard Water is a substance which does not readily form lather with soap due to some ion contaminations. It is water that contains cations with a charge of 2+, especially Ca2 and Mg2. These ions do not pose any health threat, but they can engaged in reactions that leave insoluble mineral deposits, these deposits can make hard water unsuitable for many uses, and so a variety of mean have been developed to ‘soften” hard water, that is, removed the calcium and magnesium ions.

Hardness: Hardness in water is defined as the presence of multivalent cations. Hardness in water can cause water to form scales and a resistance to soap. It can also be defined as water that doesn’t produce lather with soap solution.

2C17H35COONa ± Ca2 (C17H35COO)2Ca + 2Na

Rain water is acidic, because, it combines with carbon (IV) oxide in the atmosphere to form carbonic acids.

H20 + CO2 > H2C03

Therefore, if this rain water flows through chalk, chromate rock and limestone, it will become hard. This is because water react with calcium and magnesium salts in the rocks.

H2C03 + CaCO3 – Ca(HCO3)2

Calcium hydrogen carbonate also formed in the reaction, which responsible for the hardness of the rain water.

2.7 Softening of Hard Water

Removal of temporary hardness of water can be easily done by boiling. This hardness is caused by the presence of dissolved calcium hydrogen trioxocarbonate (IV) (Ca(HCO3)2 which decomposes on heating by forming calcium trioxocarbonate (IV) CaCO3, it is insoluble and bring the calcium ions out of the solution and as a precipitate. Once the calcium ions are out of the solution, the soap that is added to the water will be available for the formation of lather.

Ca(HCO3)2(aq) Boil> CaCO3(s) + H20(l) + C02(aq)

Temporary hardness can also be removed by using slaked lime, Ca(OH)2

Ca(HCO3)2(aq) + Ca(OH)2(s) > 2CaCO3 + 2H20(l)

Soluble Slightly soluble Insoluble

Hard water can also form carbonic acid due to the reaction of carbon dioxide with water. The minerals deposited are formed by ionic reactions resulting in the formation of an insoluble precipitate. For example, when hard water is heated, Ca2 ion react with bicarbonate (HCO3) ions to form insoluble calcium carbonate (CaCO3), as shown in equation below.

(i) Ca2 (aq) + 2HC03(aq) > CaCO3(s) + H20 — CO2

For large scale municipal operations, a process known as the “lime—soda process” is used to remove Ca2 and Mg2 from the water supply. Ions exchange reactions, similar to those performed in this experiment, which result in the formation of an insoluble precipitation of slaked lime, Ca(OH)2, and soda ash, Na2CO3, Calcium precipitates as CaCO3, and magnesium precipitate as Mg(OH)2. These solids can be collected, thus removing the scale-formation cations from the water supply.

(ii) The reactions of precipitation of Mg(OH)2 is by consulting the solubility guidelines in the experiment reveals that the Ca(OH)2 of slaked lime is moderately soluble in water to give one Ca2 ion and two OH ions for each unit of Ca(OH)2 that dissolves. The OW ions react with Mg2 ions in the water to form the insoluble precipitate. The Ca2 ions are unaffected by this reaction, and so neglected them in the net ionic reaction (equation ii). They are removed by the separate reaction with C032 ions from the soda ash.

Mg2(aq) + 20W(aq) Mg(OH)(s)

The calcium carbonate or magnesium carbonate formed is insoluble in water and does not affect the soft water obtained after boiling as represented in

the below equations.

(i) Ca(HCO3)2 Heat> CaCO3 ± CO2 + H20

(ii) Mg(HCO3)2 Hea MgCO3 + CO2 + H20

When the little quantity of slaked lime is added to the hard water, if it excess the water will become harder. The slaked lime reacts with the hydrogen carbonate of calcium or magnesium to form insoluble carbonate of cakiu. r

magnesium as represented in the equation below.

(i) Ca(HCO3)2 + Ca(OH)2 > 2CaCO3 + 2H20

(ii) Mg(HCO3)2 + Ca(OH)2 > MgCO3 + CaCO3 + 2H20

The insoluble can be removed by filtration.

Common Method for the Removal of Temporary and Permanent

Hardness of Water

Both temporaly and permanent hardness can be removed by the addition of sodium carbonate (washing soda) — NaCO3 it is a double decomposition reaction.


Ca(HCO3)2(aq) + 2NaCO3 > 2NaHCO3(aq) + CaCO3(s)

The carbonate of calcium or magnesium formed is precipitated and removed by filtration. The filtrate is called the soft water.

2.8 Causes of Hardness

(i) Calcium and magnesium salts are responsible for the hardness of water. The calcium salts are calcium hydrogen carbonate Ca(HCO3)

(ii) It can also cause by calcium sulphate (CaSO4) and calcium chloride (CaC12).

(iii) The magnesium salt are magnesium hydrogen carbonate Mg(HCO3)2 and magnesium chloride (MgCI2). Whenever any of these salts is in the water,

it means that the water is hard and would no readily lather with soap.

2.9 Determination of Total Hardness of Water

The determination of water hardness is a useful test that provides a measure of quality of water for households and industrial use. Originally, water hardness was defined as the measure of the capacity of water to precipitate soap. Hard water is not a health hazard. People regularly take hard water as calcium supplements. Drinking hard water contributes a small amount of calcium and magnesium toward the total human dietary needs for calcium and magnesium.

The National Academic of Science (1998) states that water be a major contributor of calcium and magnesium to the diet. Hard water does not cause soap scum, clog pipes and clog boilers. Soap scum is formed when the scum ion binds with soap. This causes an insoluble compound that precipitates to form the scum. Soap actually softens hard water by removing the calcium ions (Ca2) from the water.

When hard water is heated, CaCO3 precipitates out, which then clogs pipe and industrial boilers. This led to the malfunction or damage and is very expensive to remove.

(A) Water Softeners: When there is hard water, water softener can be used to remove the hardness, salt is mixed with water. The sodium ion from salt replaces the calcium ion, but this causes the water to be too salty for drinking.

(B) Complexometric Titration: Permanent hardness is usually determined by titrating it with a standard solution of ethylene diamine tetra acetic acid (EDTA) which is used for the estimation of stable cations. It is a completion or chelating agent used to capture the metal ions. This causes the water to be softened, but the metal ions are not removed from the water. EDTA simply binds the metal ions to it very tightly. It is also versatile chelating agent. Chelating agent is a substance whose molecules can form several bonds to a single metal ions. It is also the substance that binds with a metal ion to form a metal ion which results in complexion.

(C) Multidentate Ligands Method: There are many clawed holding onto metal ion to form a very stable complex. EDTA can form four or six bonds with a metal ion.


Properties of Hard Water

One of the most outstanding characteristics of hard water is its reaction with soap. If distilled water or soft water is shaken with a solution of soap or lather, foam is formed immediately, a dilute solution of soap be added drop by drop to some hard water in a bottle which is stopped and shaken after each addition. it will be found that no lather formed at first. The water is at the same time; assume turbidity is due to the formation of an insoluble precipitate. Finally after sufficient soap has been added, lather will appear. Soap are sodium or potassium salts of fatty (C17H35COONa) of high molecular weight are soluble in water, but those of calcium and magnesium are not in hard water, the ions of these elements displace the sodium, giving precipitates of that soluble fatty acids salts.


2C17H35C00 Na4 + CaSO4 > (C17H35COO)2Ca2 + Na2SO4

2.11 Advantages of Hard Water

(i) Prevention of Lead Poison: Very soften water tends to dissolve the lead pipes. The accumulative poison and continual drinking of the water produce lead poisoning. But hard water reduces the amount of lead dissolved in a given volume of water.

(ii) Health: Hard water contains calcium compounds which can be found in building of bones and teeth.

(iii) Brewing: Hard water is designable in the industries.

(iv) Drinking: Since the bi-carbonate gives a refreshing taste to water. and water is good for drinking.

2.12 Disadvantages of Hard Water

(i) Boiler Scale: Pipes are blocked and fuel wasted as a result of occurrences

of boiler scale inside the water pipe due to the action of hard water on them.

(ii) Laundry Work: It wastes soap and the salt formed changes materials.

(iii) Industries: This is a nuisance in industries by paper and photograph.



In this research work, complexometric titration is employed in the determination of Total hardness. pH of the water collected from different areas in Kajola. Odo — Oja and Araromi areas in Ikere Ekiti, Ekiti State were taken using pH meter.

3.1 Determination of Water Hardness with Ethylene Diamine Tetra-acetic Acid (E. D. T. A.)

Principle: Water hardness, due to Ca2 and Mg2 is expressed as mg/I CaCO3

(ppm). The total of Ca2 andMg2 is titrated with standard EDTA using an

Eriochrome Black T indicator. A standard EDTA solution is prepared from dried

(do not exceed 80°C) Na2H2Y.2H20 (purity 00.0 ± 0.5%). if the sample does not contain magnesium, Mg — EDTA is added to the titration flask to provide a sharp end—point with Eriochrome black T, since calcium does not form a sufficiently strong chelate with the indicator to give a sharp end—point.


Ca +Mg\ > CaY +Mg End point: Mg2 ± H1n2 > Mgln + W

MgIn + H2Y2 > MgY2 + HIn2 ±

{ Red} { Colourless} { Colourless} { Blue} The free acid parent to the indicator is H31n and that titrant EDTA H4Y.

Ethylene Diamine Tetra-acetic Acid (EDTA) forms stable complexes with many metal ions, e g Ca2 and Mg2 in aqueous solution This is done by reacting one mole of EDTA molecules quantitatively with one mole of metal ion e.g.

Ca2(aq) + EDTA (aq) > {CaEDTA}2(aq)

3.2 Water Sample Collection

Water (H20) was collected at six different locations in Kajola, Odo — Oja and Araromi areas in Ikere Ekiti, Ekiti State. The water was collected in a securely covered plastic containers filled to the brim. Each container was labeled accordingly to indicate the point of collection.

The pH and Total Hardness were determined using E.D.T.A. with Eriochrome Black T indicator. The standardization of EDTA solution was done.

Total Hardness: Determination of Total Hardness (Ca2 and Mg2) of water samples from the locations were carried out with Ethylene Diamine Tetra-acetic Acid (EDTA), as chelating agent with Eriochrome black T indicator. The most widely used chelating agent in titrations is Ethylene Diamine Tetra-acetic Acid


Result of the Experiment and Calculations Involved: The results of titration to determine the Total Hardness (Mg2 and Ca2 ) in different well water sources or locations using EDTA were tabulated in the next chapter. Also the pH for each well water source was determined.

Determination of Total Hardness using E.D.T.A. with Eriochrome Black T

Procedure: 5Oml of aliquot of the water sample was pipetted into a conical flask, add 2m1 of the buffer solution O.05m1 of the mg-EDTA solution, and add few drops of the indicator solution. Then titrate with 0.0 1M EDTA until the colour changes from wine to red to a pure blue colour.

Standardization of EDTA So’ution: The most widely used chelating agent for titration is Ethylene Diamine Tetra-acetic Acid (EDTA).

Procedure for Hardness Determination: 25m1s of the water sample was pipetted into a clean conical flask. Then 2rnls of buffer solution and 5 drops of Eriochrome black T indicator was added. Then titrate with 0.O1M EDTA until the colour changes from wine to a pure blue colour.

3.3 pH Determination

Electric pH meter (Digital) Jenway Model 3010 was used in the survey at the site of collection. It has combined an electrode which was standardized with two buffer solutions pH 4 and pH 7. The temperature of solution was taken and pH meter adjusted manually to solution temperature. The electrode was dipped into the water sample after standardizing pH recorded and electrode minsed with distilled water and dried in between sample measurement. The readings were taken for each water sample.

4.2 Result of Analysis of Different Well Water Sources

The results of analysis of hardness and pH of well water collected at different locations in Ikere Local Government Area, Ekiti State are presented in the table below:

Table VIII: Table of Results


Different Well Water Sources

Total Hardness

Values (ppm)

pH Values


Kajola (Area A)




Kajola (Area B)




Odo — Oja (Area A)


  1. 27


Odo — Oja (Area B)




Araromi (Area A)


  1. 11


Araromi (Area B)



4.3 Discussion

Hard water increases soap consumption in laundry and so the type of water to be used in washing cloth should be water with low hardness values.

Analysis shows that well water samples from Odo — Oja are the best for both laundry and domestic use. Also it is the best well water under case study that is good source of drinking if undergo microbiological and other chemical analyses.

It is more preferable to use well water from Odo — Oja with low hardness values ranging from 20.6 to 25.2pp and pH values ranging from 6.96 to 7.27 since much money will not be spent on purchase of soap in our homes.



  1. 1 Conclusion

From the analysis. the result shows that well water sample from Odo — Oja is the best for both laundry and domestic purpose because the level of hardness is very low (20.6 — 25.2ppm). Also this water can be a good source of drinking if undergoes microbiological and other chemical analyses.

Also it is preferable to use well water from Odo — Oja areas with hardness ranging from 20.6 to 25.2ppm and pH values ranging from 6.96 to 7.27 for laundry purpose, since much money will not be spent on buying soap thereby enhancing its economic value.

5.2 Recommendations

It is recommended that well water from Odo Oja area in Ikere Local

Government is the best for both laundry and drinking purpose. The hardness values ranged from 20.6 to 25.2pp and pH ranging from 6.96 to 7.27 makes it a very good source of water for drinking as it falls within the permissible level of WHO standards.

The low level of hardness also enhances its economic values in laundry purpose as much money will not be spent on soap as water in this area is not as hard as well water from Araromi and Kajola areas.

Since the project cover only raining season, it is recommended that more research should be carried out to ascertain the quality of the water throughout the year.


Afolayan S. A (1986): Chemistry Senior Secondary Schools. Macmillan Publisher.

Akinsan (1979): Certificate Chemistry, Third Edition. Hazeld Watson and Viney Limited. Pg 202 206.

Douglas A. Skoog and Donald M West (1975): Fundamentals of Analytical Chemistry. Third Edition. Holt — Saunders International Edition. Pg 737 — 738.

Gary D. Christian (2008): Analytical Chemistry. Sixth Edition, Willey Student Edition. Pg 742 — 743.

Ibitoye (1996): Quality Assessment of Domestic Water Sources.

Robert Boyle (1977): Analytical Chemistry.

Stephen A. Afolayan (1986): A New Certification Chemistry for Senior Secondaiy School, 2nd Edition. Published (1989). Pg 32 — 33.

Venon L. S., & David J. (1980): Water Chemistry. Pg 3 — 6



(i) Preparation of O.OIM EDTA Solution: Dry the purified dehydrate (Na2H2Y.2H20) at 80°C to remove superficial moisture. After cooling, weigh about 3.8g (to the nearest milligram) into a i-litre volumetric flask, dilute to the mark with distilled water.

(ii) Preparation of the Magnesium complex of EDTA 0. 1M Solution: To 37.2g of N2H2Y.2H20 in 500m1 of distilled water, add an equivalent quantity (24.65g) of M8SO4.7H20. Introduce a few drops of phenolphthalein followed by sufficient sodium hydroxide to turn the solution faintly pink. Dilute the solution to 1—litre. When properly prepared, portion of this solution should assumed a dull violent colour when treated with pH- 10 buffer and few drops of Eriochrome black T (ErioT) indicator. Furthermore, a single drop of 0.0lNaHY should cause a colour change to blue, while an equal quantity of 0.01 Mg should cause a change to red. The composition of the solution should adjust by addition of Mg2 or Na2H2Y until these criteria are met.

(iii) Preparation of Eriochrome Black T Solution: Dissolve 200mg of the solid in a solution consisting of 15m1 of triethanolamine and 5m1 of absolute ethanol. Solution should be freshly prepared every two weeks, refrigeration slow their deterioration.

(iv) Preparation of Buffer Solution, pH 10: Dilute 570m1 of aqueous NH3 (sp gr 0.90) and 70g of NH4C1 to approximately 1-liter.

(v) Preparation of NH3-NH4CI Buffer Solution, pH 10: Dissolve 3.2g N1-LCI in water, add 29m1 conc.NH3 and dilute to about 50m1. The buffer solution is best for long period of time in a polythene bottle to prevent leaching of metal ions from glass.



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