[Histonet] Dionized vs distilled water

[Smith, Allen]

Tap water varies a little from one water system to another.  It is usually a
very dilute solution of the carbonates and chlorides of calcium, sodium, and
copper.  Its pH is usually a little over 7, so it acts as a very weak base.
(Mine is 7.4)  It must be used when the  protocol calls for it.  
Distilled and deionized water contain so few ions that neither one will act
as a weak base.  For most purposes, distilled and deionized water are
interchangeable.  It is easier to contaminate a deionizing system, but one
can contaminate a distilled water system.  Small, lab-sized systems are less
likely to become contaminated with bacteria or minerals than large
building-sized systems are.  
If you need really pure water, boil 600 ml of deionized water and add 6 mg
of potassium permanganate to it and distill the water.  Discard the first
100 ml of distillate.  The next 300 ml will be very pure water, but I can
think of no biological use for it.  (Such very pure water is sometimes used
for physics experiments.)
Both distilled and deionized water pick up carbon dioxide on standing and
become weak solutions of carbonic acid.  If you work alone, its pH will
probably be 6.9; if there are several people in the lab, the pH may fall to
6.8.
	-----Original Message-----
	From: Morken, Tim - Labvision [mailto:tpmorken <@t> labvision.com] 
	Sent: Tuesday, October 28, 2003 12:53 PM
	To: 'JCarpenter764 <@t> aol.com'; histonet <@t> lists.utsouthwestern.edu
	Subject: RE: [Histonet] Dionized vs distilled water
	
	
	Distilled water is classically produced by heating water to
evaporation and subsequent condensing on a cold surface. In the process most
impurities are either evaporated off ahead of the water (in the case of most
organics), or left behind (in the case of minerals). The water is also
effectively deionized because the salts are left behind. It is fairly pure
water. To get very pure water it needs to be re-distilled several times.
	 
	Deionized water is classically passed through a salt bed or ionized
resin bed that captures the mineral ions (ie, a "water softener"). The water
is not necessarily pure, however, especially in regards to organic
chemicals. Reverse osmosis is also used now days to deionize water.
	 
	 
	High quality water systems these days are some combination of
filters, distillation, deionizing resins and reverse osmosis. 
	 
	Tim Morken
	 
	-----Original Message-----
	From: JCarpenter764 <@t> aol.com [mailto:JCarpenter764 <@t> aol.com] 
	Sent: Tuesday, October 28, 2003 7:45 AM
	To: histonet <@t> lists.utsouthwestern.edu
	Subject: [Histonet] (no subject)
	 
	while studying for my exam on the different fixatives and there
ingredients....i have noticed that some call for distilled water and some
use the term deionized water.  Is there a difference?
           
                       
                
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Barry University - Miami Shores, FL (http://www.barry.edu) 
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