Re:H2O:distilled vs deionized

Paul and Judith Simon ()
Tue, 14 January 1997 5:12 PM

<Most supermarkets here (don't know about where you are) sell gallons of
<distilled water at prices much lower than the cost to make it yourself. As
<to deionized (British: deionised) water, there are still salts in the <water,
<albeit soluble ones Jeffrey.D.Mathias@worldnet.att.net (usually sodium) and even that adds some uncertainty to
<the activity of the solutions. I use, and recommend, fully distilled water.
<Incidently, old stills used copper piping that added a bit of copper to the
<water; newer ones are glass-lined and the water is quite pure.

I beg to differ with a few of the above comments:

There are no ions left in deionized water, i.e., that's why its called
deionized, especially not sodium. Perhaps you were thinking of the common type
of household water softeners where calcium is exchanged for sodium. There are
still dissolved <non - ionic> materials, like air, and sometimes, chloramines
which are used in the US for disinfection. The quantities of these non-ionic
materials is, in my judgement, too small to have any material effect.

Also, with respect to old stills, I know that the one we had in grad school had
tin lined pipe, not copper. It would be hard for me to imagine anyone piping a
distilled water system using copper pipe. When we used deionized water systems
in the semiconductor business here in Silicon valley, the piping we used was
PVC, and now I believe they are upgrading to PDVC, and rarely teflon and such.
The main problems in these systems is accumulation of bacteria adhering to the
inside wall of the pipe, and the solution is periodic chlorination.

I would also like to add, that I live in a naturally soft water area, San
Francisco, and have never had any difficulties with the water supply in
conventional processing. The only step where it might be prudent to use
deionized water might be in the final rinse with photo-flo.

Paul Simon 70760.1511@compuserve.com

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