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Re: [APD] CO2 revelations

Chris Hotte wrote:
> Thomas Barr wrote:
>>Now KH test kit variance is one issue, making a reference standard to compare you KH test to is a very WISE idea to check the accuracy. I've seen many folks have very high CO2 predicted levels, yet fish were fine, but another than has barely 30ppm and the fish are gasping. It cannot be that both are at the same CO2ppm level becaused we would expect to see the same behavior from the fish. Instead we see very wide ranges and impacts on the fish(as well as plants).
>>So it's much more likely that it is the testing method, rather than anything else.
>>pH is the best thing as far as accuracy for CO2 measurements using a pH probe and no electrical equipment runnign when the pH is measured(stray current will depress the pH giving false high ppm CO2 levels).
>>KH test kits have consistency issues (see recent post) and in some places, although rare, non bicarbonate alkalinity exists(recent poster in NM has significant borate alkalinity, desert regions generally).
> It's not the testing method on behalf of the tester. It's not 
> contamination. It's not even a difference in temperature. Nor is it an 
> accurracy issue as was previously suggested. Doubling the sample just 
> allows me to narrow in on .5 dKH.  It doesn't "appear" to be a 
> difference in drop size. I've eliminated volume descripincies, but the 
> variance is too significant for that to come into play. 
> PH is not the issue either, as it is contant, measured with the probe in 
> or out of tank, eliminating current leak. Still that isn't the focus. 
> All things being equal, the indicator solution, though consistant gives 
> considerably different results.
> Now the mention of a KH refrence sample is very interesting. Can one be 
> made with say a saturated solution of  Sodium Bicarbonate? Or, a known 
> volume of water and weight of NaHC03 with a KH reading fixed to it.

The atomic weight of NaHCO3 is 84, and the atomic weight of HCO3 is 61. 
That means for every gram of NaHCO3 you have 726mg of HCO3. If you can 
measure out 246.5g of NaHCO3 into 1 liter of water, you should have 
179ppm HCO3 (bicarbonate). I'm not sure what the test is measuring 
exactly, but if it's bicarbonate that should do it.

Jerry Baker
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