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Why do we aim for 30 ppm CO2?
- Thread starter John P Coates
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- co2 concentration optimum plant ppm
Hi all,
Even if you don't have access to RO, distilled or DI water, you can boil a kettle of hard water, and pour the boiling water through a cotton handkerchief, muslin or "Brine Shrimp" sieve in to a bowl etc.
When the water boils it is de-gassed, and we already know know that CO2~ HCO3 are in equilibrium. When we boil the water all the bi-carbonates come out of solution (there is no CO2 and the equilibrium means that no CO2 = no HCO3 in solution) and form insoluble (usually calcium) carbonate "scale" (CaCO3).
Normally as the water cools CO2 would diffuse in from the atmosphere, and (as a small proportion enters solution as H2CO3), the "scale" would dissolve adding Ca++ and HCO3- ions.
But, if we filter out the "scale" there are no HCO3- ions to go back into solution as CO2 diffuses in and the pH will fall (this is why rain-water is naturally acid).
Once we've got our carbonate free water you can then add a soluble bi-carbonate (NaHCO3 or KHCO3) to raise the alkalinity, and in most situations alkalinity is equivalent to dKH. I won't go through the maths, but it is here: <http://www.thekrib.com/Plants/CO2/hardness-larryfrank.html>.
The bit we're interested in is adding 3.0g sodium bicarbonate (NaHCO3) to 100 litres of water will raise the alkalinity by 1 & adding 3.6g potassium bicarbonate (KHCO3) to 100 litres of water will raise the alkalinity by 1 (from
<http://www.theplantedtank.co.uk/water.htm>). So from there 12g NaHCO3 in 100 litres will be ~4dKH, or 1.2g in 10 litres of H20.
cheers Darrel
This one would do, <http://www.mn-net.com/StartpageWate...rdness/tabid/4768/language/en-US/Default.aspx>, but you don't really have to be able to measure dKH accurately, you just need to start with DI (de-ionised) water, it is pure H2O.
Even if you don't have access to RO, distilled or DI water, you can boil a kettle of hard water, and pour the boiling water through a cotton handkerchief, muslin or "Brine Shrimp" sieve in to a bowl etc.
When the water boils it is de-gassed, and we already know know that CO2~ HCO3 are in equilibrium. When we boil the water all the bi-carbonates come out of solution (there is no CO2 and the equilibrium means that no CO2 = no HCO3 in solution) and form insoluble (usually calcium) carbonate "scale" (CaCO3).
Normally as the water cools CO2 would diffuse in from the atmosphere, and (as a small proportion enters solution as H2CO3), the "scale" would dissolve adding Ca++ and HCO3- ions.
But, if we filter out the "scale" there are no HCO3- ions to go back into solution as CO2 diffuses in and the pH will fall (this is why rain-water is naturally acid).
Once we've got our carbonate free water you can then add a soluble bi-carbonate (NaHCO3 or KHCO3) to raise the alkalinity, and in most situations alkalinity is equivalent to dKH. I won't go through the maths, but it is here: <http://www.thekrib.com/Plants/CO2/hardness-larryfrank.html>.
The bit we're interested in is adding 3.0g sodium bicarbonate (NaHCO3) to 100 litres of water will raise the alkalinity by 1 & adding 3.6g potassium bicarbonate (KHCO3) to 100 litres of water will raise the alkalinity by 1 (from
<http://www.theplantedtank.co.uk/water.htm>). So from there 12g NaHCO3 in 100 litres will be ~4dKH, or 1.2g in 10 litres of H20.
and now we are into the drop checker or titrimetric situation, and you can just think of a the drop checker, 4dKH solution and bromothymol blue (narrow range pH indicator) as a titrimetric method.
cheers Darrel
