Units of hardness and their relationship, Chemistry

Q. Write short note on units of hardness and their relationship.

Sol. Units of hardness and their relationship.

(1)         Parts Per million (ppm): It is defined as the number of parts by weight of CaCO3 equivalent present in per million (106) parts by weight of water.

1 ppm = 1 part of CaCO3 equivalent hardness in (106) parts of water.

(2)         Milligrams per litre (mg/l): It is defined as the number of milligrams of CaCO3 equivalent hardness present in one litre of water.

1 mg/L = 1 mg of CaCO3 equivalent hardness present per litre of water.

It can be easily proved that 1mg/L = 1 ppm, for water

Weight of 1 litre of water = 1kg = 103g = 106mg

= 1000*1000g= 106mg

1mg/L = 1mg of CaCO3 equivalent hardness per 106 parts of water.

         1mg/L = 1 part of CaCO3 equivalent hardness per 106 parts of water.

1mg/L = 1ppm

(3)         Degree Clark (0Cl): It is defined as the parts of CaCO3 equivalent hardness per 70,000 parts of water or it is number of grains (1/7000lb) of CaCo3 equivalent hardness per gallon (10lb or 70,000 grains) of water. 10 Clark= 1 part of CaCo3 per 70,000 part of water.

(4)         Degree of French (0Fr): It is defined as the parts of CaCO3 equivalent hardness per Lac (100000) parts of water.

10Fr = 1 part of CaCO3 equivalent hardness per (105) parts of water.

(5)         Milli equivalent per litre (meq/L): It is defined as the number of milli equivalents of hardness present per litre.

1 meq/L = 1 meq of CaCO3 per L of water

                 = 10-3 * 50g of CaCO3 eq. per litre of water

                   =   10-3 * 1000 * 50 mg of CaCO3 eq. per litre of water

                 = 50mg of CaCO3 eq. per litre of water

                 = 50mg/L of CaCO3 eq. per litre of water = 50 ppm

                 = 50mg of CaCO3 eq. per 106 litre of water

                 = 1 mg of CaCO3 eq. per 106 /5 mg litre of water

                  = 1 part of CaCO3 equivalent per 20,000 parts of water.

Relationship between different units of hardness:

1 ppm = 1 part per 1000000 parts of water

1 0Fr = 1 part per 100000 parts of water

1 0Cl = 1 part per 70000 parts of water

1 mg/L = 1 part per 1000000 parts of water

1 meq/L = 1 part per 20000 parts of water

Hence: 1000000 ppm = 1000000Fr = 700000Cl = 1000000 mg/L = 20000meq/L

= 100 ppm = 100Fr = 70Cl = 100mg/L = 2 meq/L

    1 mg/L     = 1 ppm = 0.10Fr = 0.070Cl = 0.02 meq/L

10Cl = 14.3 ppm = 1.433 0Fr = 14.3 mg/L = 0.286 meq/L

10Fr = 10 ppm = 10 mg/L = 0.7 0Cl = 0.2 meq/L

1 meq/L = 50 mg/L = 50 ppm = 5 0Fr = 0.35 0Cl

Posted Date: 7/21/2012 7:04:25 AM | Location : United States







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