Steve_Warner
01-08-2005, 04:44 AM
Hi all,
While doing a little bit of fun research on chelation of Calc, Mag and other stuff, I ran across a couple of good, brief descriptions of Alkalinty. First one is cut/paste and second one is link. This partly explains why the term KH is a slight misnomer when it comes to an Alkalinity test in the aquarium. KH is widely accepted as meaning Carbonate Hardness, which is partly correct when talking about the mechanism of resisting a pH change due to acids:
"Alkalinity
Friday,Mar 31, 2000
1. The quantitative capacity of water to neutralize an acid; that is, the measure of how much acid can be added to a liquid without causing a significant change in pH.
Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have high alkalinity.
In the water industry, alkalinity is expressed in mg/L of equivalent calcium carbonate.
The following chemical equilibrium equations show the relationships among the three kinds of alkalinity: carbonate (CO32-), bicarbonate (HCO3-), and hydroxide alkalinity (OH-). Total alkalinity is the sum of all three kinds of alkalinity.
CO2 + H2O <===> H2CO3 <===> H+ + HCO3- <===> pH 4.5 pH 8.3 2H+ + CO32-
Above pH 9.5 (usually well above pH 10), OH- alkalinity can exist or CO32- and OH- alkalinities can coexist together. Different tests are used to determine the quantity of the different kinds of alkalinities present in water."
http://www.membranes.com/docs/papers/04_ro_water_chemistry.pdf
Steve
While doing a little bit of fun research on chelation of Calc, Mag and other stuff, I ran across a couple of good, brief descriptions of Alkalinty. First one is cut/paste and second one is link. This partly explains why the term KH is a slight misnomer when it comes to an Alkalinity test in the aquarium. KH is widely accepted as meaning Carbonate Hardness, which is partly correct when talking about the mechanism of resisting a pH change due to acids:
"Alkalinity
Friday,Mar 31, 2000
1. The quantitative capacity of water to neutralize an acid; that is, the measure of how much acid can be added to a liquid without causing a significant change in pH.
Alkalinity is not the same as pH because water does not have to be strongly basic (high pH) to have high alkalinity.
In the water industry, alkalinity is expressed in mg/L of equivalent calcium carbonate.
The following chemical equilibrium equations show the relationships among the three kinds of alkalinity: carbonate (CO32-), bicarbonate (HCO3-), and hydroxide alkalinity (OH-). Total alkalinity is the sum of all three kinds of alkalinity.
CO2 + H2O <===> H2CO3 <===> H+ + HCO3- <===> pH 4.5 pH 8.3 2H+ + CO32-
Above pH 9.5 (usually well above pH 10), OH- alkalinity can exist or CO32- and OH- alkalinities can coexist together. Different tests are used to determine the quantity of the different kinds of alkalinities present in water."
http://www.membranes.com/docs/papers/04_ro_water_chemistry.pdf
Steve