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The hardness of water is expressed by the amount of calcium present in water. In this method, chlorides, sulphates and bi-carbonates of calcium and magnesium and also carbonates of magnesium are not takes into consideration
Hardness is expressed by—
- PPM ( Parts per Million )
- English degree
- German degree
- French Degree
PPM: The number of grains of calcium carbonates which is present in one million grains of water is called PPM. 1 grains of calcium carbonate present in 1 million grains water. PPM can be related to degrees.
The relation is i.e. PPM=Degrees/0.07
English Degree: The no of grains of substance per one U.S gallon of water is called English Degree.
1 grain=1/7000 pound
1 US gallon of water= 8.33 pound
German Degree: Parts per hundred thousand (PP/100000)= Number of parts of substance per 100000 parts of water is called German degree.
French Degree: Grain per imperial gallon= Number of grains of substance per 1 British imperial gallon of water is called French degree.
1 grain=1/7000 pound.
1 imperial gallon of water= 10 pound.
Conversion table of different methods:
| German Degree | PPM (CaCO3) | English Degree | French Degree | |
| German Degree | 1 | 17.80 | 1.25 | 1.78 |
| PPM (CaCO3) | 0.056 | 1 | 0.07 | 0.1 |
| English Degree | 0.798 | 14.30 | 1 | 1.43 |
| French Degree | 0.56 | 10 | 0.702 | 1 |
English