So how might you verify and confirm the chart or any method?
Eg, how would you calibrate a methods such as any of these?
We can calibrate for a light meter, or a NO3 test kits by usign known standard solutions, but for CO2 dissolved in water at a specific ppm????
Well, we can use DI/RO water, and make a known stock solution of KH, say using sodium carbonate or bakign soda in say a 40 liter volume, add CO2 via a powerhead atomized well mixed tank.
This will have nothing else in the tank other than the CO2 and the carbonate KH.
So this is a referenced system.
Now we can use a calibrated accurate pH meter.
This will yield the correct CO2 based on the pH/Kh/CO2 chart.
Now..........you have a reference to compare your method against.
You can leave the flow rates the same for the RO/DI baking soda reference and add tank water, or if you have a CO2 test.......say a DC or a water sample method with 1 pH unit, you may try that, or a CO2 prove specific meter.
You may change the CO2 reference point by adding/reducing the CO2 gas injection in the referenced system.
This should get most to within 1-2 ppm of CO2.
But......requires folks to actually test and CLAIBRATE THE CO2 AND USE RO/DI WATER MAKE UP, AND A HIGH GRADE pH METER.
I think it will be tough to beat a high grade pH meter for measuring pH 😀
What you need to do is to remove the unknowns about the KH/acids etc from the tank system and see what the true CO2 is, they see about scaling that.
DC's are not the best and cannot measure pH very well at all.
Regards,
Tom Barr