Re: [APD] CO2 and pH control

["Andrew McLeod" <thefish at theabyssalplain_freeserve.co.uk>]

On Mon, 12 Dec 2005 17:21:19 -0000, Gordon and Susan Watkins <gwatkins at ritternet_com> wrote:

> I just retested with the same results. However, I'm using the Aquarium
> Pharmiceuticals test and I'm unclear whether you count the first drop
> which changes the solution blue. After color change to blue, it takes 9
> drops to turn yellow. If you count the first drop, the KH is 10. Does
> that make more sense?
>
> Gordon
>
> Jerry Baker wrote:
>
>> Gordon and Susan Watkins wrote:
>>
>>
>>> Thanks for the info Jerry. My KH and GH both measure 9.0. From your
>>> info, it sounds like my current level of 8.2 is about right.
>>>
>>>
>>
>> Only 9? And your pH is 9.3? That means there is something else in that
>> water acting on your pH other than carbonates and CO2. Your water should
>> have a pH around 7.7 - 8.0 if the KH is 9.

You should almost certainly include the first drop in a titration based test (if there is only one bottle). Basically you are adding a reactant until you have used up all of the chemical you are testing for, whereupon you will have excess reactant left. There will also be an indicator in the bottle that turns blue to yellow when this point is reached.

-- 
Andrew McLeod
thefish at theabyssalplain_freeserve.co.uk

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