Re: RO/DI Water

To: Aquatic-Plants at actwin_com
Subject: Re: RO/DI Water
From: Jonathan_Kirschner at Energetics_com (Jonathan Kirschner)
Date: 22 Jan 1997 10:36:05 GMT

Just to add my two cents to the RO/DI water thread:

Reverse Osmosis is a physical process in which water is forced by
very high pressure through specialized membranes.  Some salts and
large molecules are removed by this process, ions are not.

Deionization is a chemical process in which specialized ion
exchange resins adsorb cations and anions and give up H+ and OH-
ions in return.  These resins can generally be recharged with strong
acids and bases.  The analytical technique of ion chromatography
uses the same principle.

Most integrated circuit manufacturing processes use a combination
of RO/DI processes to produce ultrapure water (18 megaohm
resistivity).  Bacteria building up in the dead spots in the plumbing
system is a continual problem.  The bacteria may not survive long,
but their tiny little carcasses do interfere with the manufacturing of
integrated circuits whose line widths are down in the 1 micron range.
One should never drink deionized water, not only because of the
bacteria, but also because the lack of dissolved ions makes it
extremely corrosive.  Drink enough of it and it will even leach
calcium from your bones.

Jonathan