pH,
AND ALL THAT!
Ron
Knowles.
Recent~ information from severa1 sources provides valuable and
obviously authentic insight into water, distilled and de-ionised included,
in relation to its use in combination with chemicals to give a
predetermined pH value In short a buffer solution of known value by the
dedicated “weigher & mixer” this will not be just of interest but,
equally of vital importance Particularly so for those amongst us who are
sufficiently interested and dedicated to test various alternative formulae
and probably different emulsions as well For, in this way, the path could
well be cleared for those not having a pH meter, by eventually providing a
solution - in particular a colour developer which will give a suitable pH
value after the intitial mix-up without the need to adjust the value in
either direction
.After listing his experiences
with various water supplies ~ from tap water (the pH value of which can
vary considerably from day today) ‘fridge water!. (thawed from the ice
when defrosting) deionised, and distilled,. Oliver Barron in his (Area 20
Newsletter quotes some highly teqhnica1 information. for C.R.C. member
Geoff Webb. Geoff at one time had responsibility for two separate
carbonising complexesone of. Which was provided piped ‘pure’ water
from a deionised plant and the other with similar water ‘from a
distillation plant. The ion exchange plant consisted of a number of ion
exchange resin beds through which, water was passed, producing a finished
product much superior to that from the real still. Real distilled water is
a deceiver, the quality of which is rarely quoted. and always suspect. The
deception arises from the apparent fundamental simplicity of the process.
Boil the water and leave the dissolved solids behind. This theoretical
state can only exist if ALL the H20 can be in the gaseous state
when it passes to the condenser. Unforfortunate1y it. is invariably in the
wet steam state - a vapour - containing a goodly proportion of tiny water
droplets which still contain undissolved solids arid therefore adulterate
the purity of. the product.
You will gather from the foregoing that I
would always prefer a reputable (Boots’?) de-mineralised water to an
un-named distilled product. BDH do not list distilled water as such. They
list water “Analar” a laboratory reagent of quoted standard purity.
They also quote a pH range of 5.5 to 7 5 as acceptable due to the
readiness with which water dissolves C02 from the air. I recall that
samples of water from the demin. plant product stream for quality control
purposes could give an unacceptable pH reading if shaken with air
in a half-filled bottle. May I suggest you confuse the issue further by
boiling a sample of your water(s), in glass if possible, to drive of the
CO2, measure the pH and then blow your exhaled breath into the sample
through a straw and measure again
In his following Newsletter Oliver quotes from
a letter on the same theme from Alan Goldman. Alan says, in the
laboratory. in which he worked they “polished” distilled water by
passing it through a deioniser column. So both Geoff and 4lan prefer the
deionised variety. final quote from Alan. The pH of the production both
cases is dependant on the starting pH of the raw water and confusion
arises from the belief that the pH is neutral. From this you can see that
you can use either source, distilled or deionised, as long as you adjust
the pH. Personally I have always used tap water with no problems. A
further point to note is that all water on standing in an unsealed
container absorbs carbon dioxide from the air and becomes more acid over a
period of, say, 12 hours”.
From Tony Chuter, a member of Area 18, comes a
taped interview on the same topic, with a friend whose name I cant recall,
other than his first name which is Ernie - but who is the retired
principle of the chemistry dept. of Southampton, University. I quote from
the tape verbatim in question arid answer form - the questions obviously
coming from Tony.
Q. You were saying that.a pH.of
distilled or deionised will vary. I asked were it’s possible or
reasonable to bring the pH back to pH 7 if you wanted to. Would you mind
telling me again what you said about it?
A. The position
is that in water itself there is only a very small amount of impurities if
it is distilled, and it is very un-buffered which means that only a miner
amount’ of acid or alkali is sufficient to move ‘the. pH quite a lot.
Having said that one ought. to realise that the other chemicals you put in
are going to produce a pH of themselves and they will SWAMP
anything that is in the water. Anything that is in the water which might
take the pH a unit either way of pH 7. forget it If you try to calculate
how much acid or alkali you put in you would probably have to take &
thousanth of one per cent of caustic soda and then take a tiny pin-prick
of that and that would be sufficient to send the pH up to 8 from 7.