substances that apart from distilled water,
it’s seldom found in anything like pure
form. Tap water is quite variable in
composition, depending on its ultimate
source (well, lake, river) and its municipal
treatment (chlorination, fluoridation, and
so on). Two common minerals in tap water
are carbonate (CO3) and sulfate (SO4)
salts of calcium and magnesium. Calcium
and magnesium ions are troublesome
because they react with soaps to form
insoluble scums, and because they leave
crusty precipitates on showerheads and
teapots. Such so-called hard water can also
affect the color and texture of vegetables,
and the consistency of bread dough (pp.
282, 535). Hard water can be softened
either city-wide or in the home, usually by
one of two methods: precipitating the
calcium and magnesium by adding lime, or
using an ion-exchange mechanism to
replace the calcium and magnesium with
barry
(Barry)
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