Chemistry guru wanted

[Anonymous]

A buffer is a mixture of an acid and its base salt. For example, sodium acetate and acetic acid.

The pKa is the pH at which the concentration of free acetate ion is the same as protonated acetate ion. That is the point at which a particular buffer works the best. A buffer, when it is working, tries to restore the solution to the original pH, so if you put a little more acid in, the pH won't move very much.

Ideally you want to use a buffer whose pKa is about the same as the pH you are aiming for. So if you want your pH to be 8, you don't want to use something that has a pKa of 5.

 

[danmhippo]

So, where can I go to find a chart of pKa of the solutions out there? For example, if I want to maintain pH at 6.4, then if I read correctly, I should find a buffer whose pKa is around 6.4??

Is that right?

 

[Anonymous]

Yes, you are getting the idea there, Danm. For a table of pKa, you can do a search online, or look it up on CRC Reference for Physics and Chemistry (your local library has it, if you don't have one next to a Yellow Page at home).

As mentioned above, make sure the buffer is
1, easy to work with (non-toxic, etc.)
2, does not cause interaction with other chemicals / livestocks
3, does not prompt DHLS to visit you

 

[Anonymous]

carbon dioxide dissolved in water and baking soda has one (of two) pKa's right around 6.4

 

[danmhippo]

So in addition to CO2 that I am currently using, should I also try to find a proper dosage (by trial and error) of adding baking soda?

(BTW, I always thought baking soda is alkaline.......)


Before I forget, for both of you, thank you very much.

 

[HClH2OFish]

Just add tons of plants...I heard they cure everything...


/runaway mode

 

[danmhippo]

LOL!



(Oooooki Doki, you are on my ignor list from now on...........) :mrgreen:

 

[Anonymous]

It really doesn't matter what acid you use. The trick is to adjust the pH first and then put it in the tank. So you could take a few spoonfuls of baking soda, dissolve it in water, and add hydrochloric acid drop by drop until you get to the pH you want. It might be worth doing this as an experiment, especially if you have a pH meter, and graph the result. What you will see is that the closer you get to the pKa, the harder it is to change the pH. That in essence is what a buffer is.

 

[Anonymous]

This link shows titration curves for various acid/base combinations.