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    Hardness of Water

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    slchem
    Hardness in water can be defined as the characteristic that prevents the lathering of soap and can be temporary or permanent. Temporary hardness is caused by calcium and magnesium bicarbonates and can be removed by boiling water, causing the bicarbonates to precipitate out as insoluble carbonates. Permanent hardness cannot be removed by boiling and is caused by dissolved chlorides, nitrates, and sulfates of calcium, magnesium, and other metals. Hardness in water is quantified using units like parts per million, milligrams per liter, degrees Clarke or French, which express the amount of calcium carbonate equivalents in the water.

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    Hardness of Water

    Uploaded by

    slchem
    852 views3 pages
    Hardness in water can be defined as the characteristic that prevents the lathering of soap and can be temporary or permanent. Temporary hardness is caused by calcium and magnesium bicarbonates and can be removed by boiling water, causing the bicarbonates to precipitate out as insoluble carbonates. Permanent hardness cannot be removed by boiling and is caused by dissolved chlorides, nitrates, and sulfates of calcium, magnesium, and other metals. Hardness in water is quantified using units like parts per million, milligrams per liter, degrees Clarke or French, which express the amount of calcium carbonate equivalents in the water.

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    Hardness in water can be defined as the characteristic that prevents the lathering of soap and can be temporary or permanent. Temporary hardness is caused by calcium and magnesium bicarbonates and can be removed by boiling water, causing the bicarbonates to precipitate out as insoluble carbonates. Permanent hardness cannot be removed by boiling and is caused by dissolved chlorides, nitrates, and sulfates of calcium, magnesium, and other metals. Hardness in water is quantified using units like parts per million, milligrams per liter, degrees Clarke or French, which express the amount of calcium carbonate equivalents in the water.

    Copyright:

    © All Rights Reserved
    852 views3 pages

    Hardness of Water

    Uploaded by

    slchem
    Hardness in water can be defined as the characteristic that prevents the lathering of soap and can be temporary or permanent. Temporary hardness is caused by calcium and magnesium bicarbonates and can be removed by boiling water, causing the bicarbonates to precipitate out as insoluble carbonates. Permanent hardness cannot be removed by boiling and is caused by dissolved chlorides, nitrates, and sulfates of calcium, magnesium, and other metals. Hardness in water is quantified using units like parts per million, milligrams per liter, degrees Clarke or French, which express the amount of calcium carbonate equivalents in the water.

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    of 3

    WATER

    HARDNESS

    THEORY

    HARDNESS- can be defined as the soap consuming


    capacity of water sample OR it is the characteristic that
    prevents the lathering of soap.

    eg. 2C17H35COONa +
    CaCl2
    2 NaCl
    Sodium stearate
    Hardness
    Soluble soap
    i.e. Long chain fatty acids.

    Ca [C17H35COO]2

    Calcium stearate
    Insoluble soap
    i.e. Precipitate.

    (soaps are sodium salts of fatty acids)

    TYPES OF HARDNESS
    I.

    Temporary hardness

    the hardness which


    can be removed by boiling and filtering is referred as
    temporary hardness or bicarbonate hardness.

    When water containing Ca & Mg bicarbonates is heated,


    soluble bicarbonates are converted into insoluble carbonates &
    hydroxide. On filtering of such water, soft water is obtained.

    Ca(HCO3)2 ------ CaCO3 + H2O + CO2


    Calcium bicarbonate
    Calcium carbonate
    Soluble
    Insoluble

    WATER

    HARDNESS

    II.

    THEORY

    Permanent hardness

    the hardness which


    cannot be removed by boiling the water sample is
    referred as permanent hardness.

    It is caused by dissolved chlorides, nitrates &sulphates of


    calcium, magnesium & other heavy metal ions. Permanent
    hardness can only be removed by lime-soda, ion exchange or
    zeolite process.
    CaCl2 + Na2CO3 --- CaCO3 + 2NaCl

    UNITS OF HARDNESS
    Hardness in water is express in terms of calcium carbonates
    equivalents per liter because the molecular weight is 100 & it
    forms precipitated during water treatment & it is insoluble in
    water.
    1) Parts per million(ppm)-It can be defined as the
    number of parts of CaCO3 present in 1 million parts of
    water.
    1 million = 106 parts
    2) Milligram per Litre(mg/L)- It is number of milligrams of
    CaCO3 equivalent of hardness present per lime of
    water.
    3) Clarke`s Degree(oCl)- It is number of grains (1/7000 lb)
    of CaCO3 equivalent of hardness per gallon (10lb) of
    water.
    4) Degree French(oFr)- It is parts of CaCO3 equivalent of
    hardness per 105 parts of water.
    5) Milliequivalent per Litre(meq/L)- It is number of
    milliequivalent of hardness present per litre.
    Relationship between various units of hardness
    1ppm=1mg/L=0.1oFr=0.07oCl=0.02meq/L
    2

    WATER

    HARDNESS

    THEORY

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