Aeration

[cgin40]

I understand that aeration increases PH. Can someone explain why? Curious minds would like to know.

Along those lines, would borax help stabilize PH in an outdoor pool with a water fall?

Dave

 

[JohnT]

Aeration allows carbon dioxide that is dissolved in the water to more easily outgas. The carbon dioxide leaving causes the pH of the water to rise.

Borates can help stabilize your pH. It's not magic, but if you are interested, read So you want to add borates to your pool--Why and How

 

[Richard320]

It's exactly the same principle as shaking a can of Coke. It's not as concentrated as the Coke, so you don't see it erupt and fizz, but it's releasing the gas and the pH rises.

 

[chem geek]

Carbon dioxide that outgases is the same thing as removing carbonic acid from the water because of the following equilibrium:

H₂CO₃ <---> H₂O + CO₂(aq)
Carbonic Acid <---> Water + Aqueous Carbon Dioxide

Removing an acid from the water raises the pH because the bicarbonate in the water (mostly measured as TA) is in equilibrium with the carbonic acid so the following moves to the right consuming hydrogen ion so raising the pH (since pH is a measure of the amount of hydrogen ion in the water):

+TA .... -TA
HCO₃^- + H⁺ <---> H₂CO₃
Bicarbonate Ion + Hydrogen Ion <---> Carbonic Acid

The TA does not change with this process because carbonic acid is a weak acid so the drop in TA from the loss of bicarbonate equals the gain in TA from the loss of hydrogen ion (i.e. from the gain in pH).

Aeration increases the rate of carbon dioxide outgassing because it increases the surface area of the water/air interface so the exchange of carbon dioxide from water to air can occur faster.

 

[sere81]

I love this site. You get some easy to understand answers and then hard core science to close the book on it.