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re: What was I thinking on Di-H2O

>Date: Fri, 20 Nov 1998 02:05:01 -0900
>From: "Romeo Shayne Pavlic'" <bcpi@arias.net>
>Subject: What was I thinking on Di-H2O
>Having taken all kinds of Chemistry in college, I am not sure why I made the
>mistake of saying Di H20.  As several of you pointed out you want to use
>Distilled H20.  Not Di H20.  Distilled H20 has the minerals taken out
>whereas Di-H20 has the ions (charges) taken out.  Thanx for pointing out my
>errors folks.  I have always used Distilled H20, not Di-H20.  And yes, I do
>get it at Safeway by the case.
>TA, Shayne.
>P.S.  I think my brain was thinking Di = Distilled not Di = De Ionized.

Minerals vs. ions? A false dichotomy: the minerals dissolved in water _are_
largely ionic compounds. With some minor exceptions, both
procedures--distillation _and_ deionizing resins--are able to remove these.
The difference is that ion-exhange resins can remove _only_ electrically
charged solutes (ions) from water, whereas distilling can remove most ionic
cmpds as well as much dissolved (or suspended) substances that are
electrically neutral (and have a high boiling point)--organics like sugars,
certain hydrocarbons, micoorganisms, dirt,  etc.

People who need very high-purity water will usually distill it multiple
times or add a final deionization step (as Bob Myers mentioned). In some
high-capacity distilling systems (supplying an entire laboratory complex)
the delivery system's metal-pipe plumbing will allow the distilled water
possibly to become a bit recontaminated before it reaches the tap. So
deionization is then a convenient extra measure (under the control of the
end-user) to assure a low level of ionic impurities. Yes, often an
"overkill" measure.

As to the corrosion of stainless steel in contact with deionized
water--I've heard of that, but wonder why similar (corrosion) wouldn't
happen with good distilled water?

         *  Phil & Judy Rose           Rochester, NY  *
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         *        mailto:pjrose@servtech.com          *