Question related with destilled water

charles francis delwiche cdelwich at
Thu Jun 17 11:02:15 EST 1993

This question has been pretty thoroughly answered, but here's my $.02:

Another problem with distilled water is accurately measuring the pH.
Both pH paper and pH meters are intended to be used with reasonably
well buffered solutions.  Distilled water is poorly buffered to say
the least, so one can get unpredictable results trying to measure the
pH.  I would consult the manual to your pH meter -- some specify
minimum solute concentrations or provide suggestions for measuring pH
in very diluite solutions.  You might even call the manufacturer if
you are really worried.

As has previously been noted, dissolved CO2 will drop the pH, and
milli-Q water, though exceptionally pure, still has dissolved gasses
in it.  *Distilled* water can have volatile hydrocarbons in it (they
will co-distil with the water), though these are usually only
important in applications where you might unintentionally concentrate
them, e.g. HPLC, and shouldn't affect the pH significantly.

Beware of storing water in plastic carboys if you are using it for
plant tissue culture.  Polypropylene is OK, but regular plastic
carboys have plasticisers (pthallates) that are potent inhibitors of

Charles F. Delwiche       |  'O Oysters, come and walk with us!'
Dept. Biology, I.U.       |      The Walrus did beseech.
Bloomington, IN 47405     |  'A pleasant walk, a pleasant talk,
[delwiche at]|      Along the briny beach'. -- L. Carrol

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