RE: keeping PH low

["David A. Youngker" <nestor10@mindspring.com>]

-----Original Message-----
From: the dude (coby)
Sent: Monday, October 28, 2002 1:32 PM

> If I use peat it brings it to that PH and
> just keeps it at 6.5...

Forgive me if I missed mention of it in previous posts, but how are you
"using peat"? The particular method doesn't sound too awfully effective if,
say

[mentioning the use of acid and its rebound]
> IT goes even faster when I have sand or
> gravel and plants in a tank. the ph starts
> rising within the hour...

it may be competing with some sort of soluble buffer. Have you tested the
sand or gravel for an acid reaction?

Dropping the pH below neutral is something a little unexpected for carbonate
buffers. Only bringing the pH down to 6.5 is a little off-beat for peat as
well. But put the two _together_ and perhaps the acidic nature of the peat
is being offset by a slightly basic reaction from the substrate.

> Even in a tank with just water, I use a HCL
> to bring the ph to maybe even as low as 3.8
> and it just starts climbing. in a week it
> will be at 6...

You have a good starting point with the tap water you've described, and the
reactions are perhaps easily explained once the substrates are examined. I
_do_ remember recent mention of pool filter sand, but I'm not sure if you're
the proper connection to it. Just in case, it tends to be fairly, if not
completely, inert, as with a straight silica or quartz sand. Otherwise it
would reaction to your pool's chemistry and start dissolving in a hurry -
which doesn't make for a very effective filter media.

That last one's a "stumper", though. The pH, hardness and conductivity
readings you've stated infer that the water has practically zip for a
buffer. If you assume a starting pH of neutral at atmospheric equilibrium,
then at the neutral point there's a 3:1 carbonic acid-to-bicarbonate ratio.
Atmospheric equilibrium achieves a "whopping" 0.5 ppm CO2, so that means you
have all of about 1.5 ppm bicarbonates in your water.

Muriatic acid would have absolutely no problem consuming such a minute
concentration of buffer. If you're adding enough acid to achieve a pH of
3.8, than "all of that buffer" is but a fleeting memory ;-) . And that
hydrogen concentration isn't going anywhere on its own, any more than it did
when it was still in the bottle marked "acid".

There's got to be a little more to this than just acid, water and a tank.
Once we have all of this ironed out, then we'll be a little more effective
at deciding on a course of action.

(Hey - since you obviously have a good, strong acid to hand, definitely try
_it_ on the substrate...)


-Y-

David A. Youngker
nestor10@mindspring.com



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