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Distilled water & Deionized water


#1

Could someone help me in understanding the properties of distilled
water and deionized water? Someone I spoke with said that deionized
water was corrosive. It would seem to me that it would be less
corrosive since it doesn’t contain the ions or minerals that other
water has. Enlighten me.

Bob Staley
B.Staley, Goldsmiths
Precision Laser Welding


#2

Hi Bob,

There is a post about distilled water and deionized water on the
following site:

http://www.madsci.org/posts/archives/jul99/931496543.Ch.r.html

Hope it helps,
Diane
http://www.sweetgemstones.com


#3

Bob, I don’t know the chemical properties, but back in my old days as
a repairman on Large water cooled computers, we used Deionized water
in the closed loop of the cooling system. It did not attack the
plumbing as much as regular water.

As to where to get it, I seem to remember getting it once at a
grocery store. I haven’t seen any that I remember lately though.
You might check with your local IBM service organization and see if
they would steer you to a source.

Don


#4

Bob,

Distilled water is produced by running water through a resin column
that contains positive or negatively charges. Thus, an impurity like
sodium chloride, or NaCl, has positive Na ions and negative chloride
ions. These ions and others, like calcium chloride, calcium
carbonate, etc., will be attracted to their opposite ion charge in
the resin. (the neg. ions attach to positive resin ions, and vice
versa) Deionized water theoretically has all the minerals removed,
but is not pure from the standpoint that the water may contain
organic compounds, which have no charge and therefore are not
attracted to charged resin.

Distilled water, on the other hand, is pure water-all the minerals
and organics have been removed.

You might be able to obtain deionized water from a lab at Emory
University or the CDC or the Ga. State Dept. of Public Health labs.


#5

I am not a water person but yes deionized water is corrosive.
Deionized water is what you will probably get if you buy “distilled
water”. Pure water doesn’t stay pure very long unless you teke
exceptional care. For practical everyday purposes fairly low purity DI
water is ok even if it gets a little contaminated. The water readily
picks up gases from the atmosphere and will pick up any metal ions
available. Superpure water will also grow bacteria which can be a big
problem in making semiconductors. In Semiconductor manufacture really
hi grade DI water is an essential utility. In these factories or
"Fabs" very hgh quality is produced and piped through avery
carefully designed plastic piping loops. The water is continuously
circulated past each use point . Water (not used water) returned from
the loop is returned to may be rtecycled through a deionizing step.
This water is also Ozonated wthru UV radiation to keep the bacterial

From growing. If you really need more , I will try to put together a
better story. Jesse


#6
Could someone help me in understanding the properties of distilled
water and deionized water? Someone I spoke with said that deionized
water was corrosive.  It would seem to me that it would be less
corrosive since it doesn't contain the ions or minerals that other
water has.  Enlighten me.

G’day; Distilled water might contain small amounts of other volatile
substances, but very little minerals. For instance if one distils
say, beer, without the elaboration of special fractionating columns,
the distillate will contain water of course, but also ethyl alcohol,
ethyl acetate, butyl alcohol, and so on - a whole swag of small
amounts of other volatile substances. Thus distilled tap water will
contain a small amount of volatile contaminants, but will be
reasonably pure for most purposes.

Water is de-ionised by passing it through glass columns containing
deionising resins, and the output will contain no metal salts, acids
or alkalis or other substances which ionize when dissolved in water.
But it may - and probably will - contain substances which do not
ionize.

If extra pure water is required, then distilled water is used to
dissolve a small amount of potassium permanganate, a little alkali is
added, and the liquid is boiled and re-distilled using a good
fractionating (separating) column. The permanganate oxidizes any
organic material in the water, and the distillate is very pure.

For ultra pure water, the water obtained by re-distillation over
alkaline permanganate is passed through deionising columns. This will
also remove carbon dioxide. BUT! as soon as the water is allowed
to contact the atmosphere it will start to dissolve carbon dioxide,
and this will ionize at once. Water thus containing carbonic acid is
corrosive; this is how caves are formed in limestone country.

I used to work with pure waters at one time, and the ionization is
measured by passing a small electric current through it via platinum
electrodes to measure resistance. Distilled water had a resistance
of 58 thousand ohms per square centimetre of electrode at a distance
of one centimetre apart. Deionised water had a resistance of 4
million ohms.

For most purposes, either distilled or deionised water is
satisfactory.

If pure water is wanted, then don’t get it from a garage,( who sells
it to top up batteries.) Many tend to fill the bottle with either tap
or rain water. I have proved this! Get either distilled water or
deionised water from the local pharmacy. If you need a lot, then get
a deionising unit from a laboratory supplier, or from a specialist in
purifying water. Most photographic processing labs use deionised
water, and have a small unit on the premises. -Yes, I know it’s a bit
long - but you did ask to be enlightened! Cheers – John Burgess;
@John_Burgess2 of Mapua Nelson NZ