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With hard water, soap solutions form a white With hard water, soap solutions form a white precipitate (soap scum) instead of precipitate (soap scum) instead of producing lather, because the 2+ ions destroy producing lather, because the 2+ ions destroy the surfactant properties of the soap by forming the surfactant properties of the soap by forming a solid precipitate (the soap scum). A major a solid precipitate (the soap scum). A major component of such scum is calcium stearate, component of such scum is calcium stearate, which arises from sodium stearate, the main which arises from sodium stearate, the main component of soap:component of soap:

2 C2 C1717HH3535COOCOO-- + Ca + Ca2+2+ → (C → (C1717HH3535COO)COO)22CaCa

TYPES OF HARDNESSTYPES OF HARDNESS

TEMPORARY HARDNESSTEMPORARY HARDNESSCaused by the presence of dissolved Caused by the presence of dissolved

bicarbonate chemicals. When bicarbonate chemicals. When dissolved these minerals yield dissolved these minerals yield

calcium and magnesium cat ions and calcium and magnesium cat ions and carbonate and bicarbonate anions . It carbonate and bicarbonate anions . It can be removed by either boiling the can be removed by either boiling the water or by addition of lime through water or by addition of lime through

the softening process. the softening process.

PERMANENT HARDNESSPERMANENT HARDNESSCaused by the presence of calcium Caused by the presence of calcium sulphate and magnesium sulphate sulphate and magnesium sulphate which do not precipitate out while which do not precipitate out while boiling. Ions causing permanent boiling. Ions causing permanent

hardness can be removed by using a hardness can be removed by using a water softener or Ion exchange water softener or Ion exchange

column. column.