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Re: [APD] chemical query

Stuart Halliday wrote:
> I believe Ade Lau wrote this email section below:
>> Stuart,
>>     Carbonate and bicarbonate are different buffer (acid base 
>> chemistry).  Carbonate is more basic than bicarbonate.  If carbonate are 
>> to use as buffer, the pH of the water will stay high.  I think at least 
>> 2 to 3 points.  Unless your water is very acidic, carbonate is not a 
>> good choice.  When carbonate gains a H+, it becomes bicarbonate.  When 
>> bicarbonate gains a H+, it becomes carbonic acid (H2CO3 --> CO2 + H2O). 
>> Of course, it is not as straight forward as it looks because they exist 
>> as an equalibrium (balance) and it takes a large change on one side of 
>> equalibrium to shift the balance.  I am not an analytical chemist, they 
>> can probably explain it better. 
>> Ade
> Thank you Ade, Jerry and Liz for your kind answers :-)
> So basically potassium bicarbonate has the edge as it dissolves quicker and 
> releases CO2?

Bicarbonates are usually easier to dissolve than carbonates. Either will 
release CO2 when first added to acidic water. The carbonate will 
liberate twice as much, all things being equal. Unfortunately, it's a 
lot more complicated than that.

> My Tap water has a ph of 6.4 and a KH of about 2d, GH pretty close to zero.

If it were my tank, I'd use some calcium and magnesium carbonate, both 
of which can be bought at a health food store in powder form. Potassium 
nitrate for nitrates, potassium phosphate for phosphates, and potassium 
sulfate can be used if potassium levels are a problem.

> I've also heard that Potassium carbonate removes chlorine from tap water as 
> well. I wonder if Potassium bicarbonate does?

I can't see how that would work. Hydrogen peroxide does remove chlorine. 
The reaction is very slow if the pH is below 7 though. I can't see how 
your tap water is below 7.0 as most jurisdictions require something 
above that to keep lead from leaching out of the pipes into your water.

"Drilling wells is boring."

Jerry Baker
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Aquatic-Plants at actwin_com