Sulphate is a naturally occurring acid radical (anion) present in all kinds of natural waters, ranging from a few milligram to several thousand milligram per litre. Excess of Sulphate content should not be there in drinking water as they cause cathartic action. Sulphate is generally found in water in the form of its salts like CaSO4, MgSO4 and Na2SO4. The desirable maximum limit for human consumption is 200 mg/ dm3.
Sulphate present in water sample is not suitable for boilers as it leads to scale formation and hence corrosion. If the amount of sulphate present in water sample is more, sulphate resistant cements are to be used for the construction purpose. Sulphate present in water sample can be determined using the following two methods,
1. Colorimetric estimation using Colorimeter.
2.Gravimetric method.
Colorimetric estimation of Sulphate:
Sulphate is estimated using barium salt of chloranilic acid. The reaction between water sample containing sulphate and barium chloranilate in ethanol medium at pH= 4 is
Sulphate present in water sample is not suitable for boilers as it leads to scale formation and hence corrosion. If the amount of sulphate present in water sample is more, sulphate resistant cements are to be used for the construction purpose. Sulphate present in water sample can be determined using the following two methods,
 |
| Digital Colorimeter |
2.Gravimetric method.
Colorimetric estimation of Sulphate:
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| Chloranilic acid |
SO42- + BaC6Cl2O4 + H+ ------- BaSO4 + HC6Cl2O4-
The amount of acid Chloranilate ion liberated is proportional to the concentration of sulphate present in water. The acid chloranilate ion at pH=4 is dark purple colour and its absorption is measured at 530 nm.
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