>
> I have lost my source for distilled water. This summer The Biology
> Department here decided to shut down the old still that supplied
> distilled water throughout the building. They did this because
> stills, especially big ones are a pain to keep clean and running; now
> it's every lab for themselves. I have found that my processing
> chemistry, film developers in particular, lasts much longer when mixed
> using distilled water. I also gain a certain degree of portability
> when I use distilled because my developing times are the same in one
> place as they are in another.
>
> I am torn between buying a small still or a demineralizer or a
> deionizer (the kind of units that use resin cartridges-like the
> Barnstead systems). Stills are very expensive and produce only small
> volumes but somewhere I seem to recall reading that deionized water
> could present problems with certain developers. I have searched high
> and low for the reference but without success. Has anyone heard
> anything like this about deionized water? Is anyone using deionized
> or deminerlized water to mix their chemistry?
>
> -greg
>
> >===for PGP Key finger Greg Schmitz <gws1@cunix.cc.columbia.edu>===
> :: ::
> Key fingerprint = 73 D3 91 15 96 69 74 E5 14 51 71 44 C8 ED 01 11
> Key ID: A7026B1D Key Size: 1024 bits Created: 1994/11/10
> ==================================================================<
>
Distilled water is very pure because it is boiled to turn it into steam
and the vapors are then condensed back into water through cooling. It is
slightly acidic due to dissolved carbon dioxide from the air producing
carbonic acid in the water. Deionized water has dissolved salts removed
by passind it through a column containing certain resins. This removes
ions but leaves anything organic or anything in a molecular form that is
in the water. This includes minerals, which are present in the form of
salts, if the water is clear to start with. I have not heard of any
problems using deionized water for photochemistry, but maybe someone else
on the list has more experience with this. I believe a deionizing column
inb line with the water supply is the most cost effective solution to the
problem. It need not be on the main supply to the whole lab jseigel@panix.com (it is not
necessary for washing, etc.) but can be plumbed into one outlet to supply
purified water for mixing chemistry.
Hope this is of use to you.
John
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