Borate

[Cory]

I know Seachem elevates their borate, for ph purposes.

Is it better to have a higher borate level to keep the ph from dropping too low? Would this be good for calcium reactors?

If you use elevated borate supplements like seachems, isn't it better to keep your alkalinity at 9dkh to account for the boron alkalinity, thus having the appropriate carbonate alkalinty?

Maybe some tank waters borate is higher but carbonate alk is actually 6dkh which is too low no?

 

[jason2459]

Here's a good read some guy wrote.

Chemistry And The Aquarium: Boron In A Reef Tank
http://www.advancedaquarist.com/2002/12/chemistry

 

[Cory]

Here's a good read some guy wrote.

Chemistry And The Aquarium: Boron In A Reef Tank
http://www.advancedaquarist.com/2002/12/chemistry

Was a good refresher thanks. Ive read that one years ago but had forgotten about it. Btw it was rhf who wrote it.

Its a good thing i dont dose boron considering it can be toxic in high amounts.

Yes i see how elevated boron can confound an titration reading if too high since they measure total alk from carbonate/bicarbonate and boron.

Im confused what pka is?

 

[jason2459]

Was a good refresher thanks. Ive read that one years ago but had forgotten about it. Btw it was rhf who wrote it.

Its a good thing i dont dose boron considering it can be toxic in high amounts.

Yes i see how elevated boron can confound an titration reading if too high since they measure total alk from carbonate/bicarbonate and boron.

Im confused what pka is?

lol yes, I know it was from Randy.

Quick tip on finding anything important

in google seach just type in

aquarium "topic of interest" Randy Holmes-Farley

He's most likely written an article about it.
lol


pka = ~pH


http://kordella.weebly.com/uploads/8/6/0/4/8604167/6_ph_and_pka.pdf

 

[Randy Holmes-Farley Verified Community Expert]

Im confused what pka is?

pKa is the pH at which the acid or base is half protonated and half not.

So for acetic acid with a pKa of 4.76, at that pH, half is acetic acid and half is acetate.

In this case, at the pKa of boric acid/borate, half is boric acid and half is borate.

Below the pKa, more than half is in the protonated form (e.g, boric acid).

 

[JimWelsh]

Since, as they say, a picture is worth 1,000 words, I'm trying to help answer @Cory's question with an image. This shows relative distributions of different species of the carbonate system and the borate system vs. pH. I've circled the the places where you can find the two pKa values for the carbonate system and the one for the borate system:

 

[Cory]

Thanks guys. Is pka basically another word for equilibrium of an elements various forms?

 

[JimWelsh]

The pKa is a particular form of an equilibrium constant, for the equilibrium between a weak acid and its conjugate base. It can be used to determine how much of a weak acid is dissociated at a particular pH, or to calculate how much of a weak acid plus how much of its conjugate base are needed to create a buffer with a specific pH value, or what the pH of a solution will be for a given concentration of a weak acid. Google the Henderson-Hasselbalch equation.

EDIT: The pKa is also equal to the pH where a buffer has the greatest resistance to a change in pH with the addition of a strong acid or base. For example, look at how the leftmost point I circled in the image in the post I made above, the pKa for carbonic acid, is just a little below a pH of 6. Now, look at the graph below that I borrowed from Randy's article about his DIY Alkalinity test. Notice how the flattest part of the titration curve is in the same pH range as the place where the CO2 and HCO3- lines cross above -- right below a pH of 6? That's not an accident. The carbonate buffering system resists change most strongly at a pH equal to its pKa. It's the same phenomenon manifesting in different ways.