"willshak" wrote in message
...
On 12/8/2004 4:43 PM US(ET), David_T (MO) took fingers to keys, and typed
the following:

SMSU BS degree with a Biology major, Chemistry minor, went back and
completed all the requisites for a chemistry major, went back again and
got a second Computer Science major with a Math minor. 20 years in the
water production industry. I'm now Senior Analyst in our Lab.

I'll have to respectfully disagree with your statement on calcium.

Since this is not a technical forum I tried to put my explanation in
non-technical terms. Corrosion within household plumbing can be from
physical as well as chemical causes. A small amount of scale build-up
on the inside of metallic pipe can protect the pipe material from both
forms of corrosion. Removing that protection by softening and you
expose your pipes to potentially corrosive water. If you wish a
technical explaination of the chemistry of that removal...

CaCO3 (solid) - Ca++ + (CO3)-- (Hard to write stoichiometeric
equations in ASCII.)

Reduce the concentration of one component from one side of the equation
(say Ca by softening) and the water chemistry will force a balance by
dissolving solid CaCO3 (scale) until a new stoichiometeric equilibrium
is reached. Continue to soften and all the scale within the pipe (and
water heater) will be dissolved over a relative short period of time
(depending on how thick the build was to begin with). This process also
works in the reveres and explains how cave formations are made. CO2 for
the air dissolves into the highly mineralized water getting ready to
drip from a cave ceiling (which begs the question how does it get
highly mineralized if scale can't dissolve back into water),
dissociates H20 to form a mild carbonic acid. The carbonate
concentration increases on the right side of the equations (forcing the
balance towards the solid), combines with Ca ions to precipitate CaCO3
(limestone and scale are pretty much the same thing you see) which
creates those beautiful formation found in limestone caves throughout
the world.

Water is the ultimate universal solvent (if it weren't, life would not
have evolved on this plant). That means almost everything will dissolve
in it to some extent (even glass). Water in its purest form, when
exposed to air, will have a pH around 5.5 Units. That's fairly acidic
as such things go and therefore naturally corrosive in my book. As
water passes over natural stone it will dissolve minerals from the
stone (this also qualifies as being corrosive to the stone). These
dissolved minerals can help buffer water's natural corrosive nature so
that when a particular compound reaches equilibrium between the
dissolved ions and the solid (using the stoichiometeric equation as an
example for CaCO3) no more solid will dissolve, i.e. the water is
non-corrosive to that solid. Disrupt the equilibrium (by removing Ca
via ion exchange softening) and the water is once again corrosive to
that solid, in this case, scale.
Sorry for the lengthy chemistry refresher. ;-)

Yeah, but, why is the ocean blue?

same reason the sky is blue