# Potassium carbonate



## happi (Dec 18, 2009)

i am thinking about using potassium carbonate to see if it will have any effect on plants, i have heard it does not effect the PH and only raise KH and potassium. i know ADA use the same thing and am sure there is a benefit of adding it to the tank, i think they also use Calcium carbonate under their soil for slow release of Ca and Kh, but for right now i am going to try the potassium carbonate. 

my question is if anyone can help me understand how i can do the following:

i want to make 500ml solution, each 20ml dose adding 3ppm of potassium and not sure how much Kh it would add to 50 gallon water. if you could help me on this i would appreciate it.

thanks to *Jeff5614 *to give me this idea.


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## KH2PO4 (Jul 18, 2009)

Add K2CO3 25088.8905090477 mg (25 grams approx.) to make 500 ml solution.

This will give you 3 PPM of K per 20 ml for a 50 US gallons tank.

3 PPM of K from K2CO3 will give you 0.21514221516 dKH.


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## happi (Dec 18, 2009)

KH2PO4 said:


> Add K2CO3 25088.8905090477 mg (25 grams approx.) to make 500 ml solution.
> 
> This will give you 3 PPM of K per 20 ml for a 50 US gallons tank.
> 
> 3 PPM of K from K2CO3 will give you 0.21514221516 dKH.


thank you, 0.2ppm of Kh per dose isn't bad at all. one more question, i have heard potassium carbonate can react if there is any kind of acid in the water which will cause it to raise the PH as well. what kind of acid is it talking about? in my solution mix i use ascorbic acid and potassium sorbate, will they react with the potassium carbonate??


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## Darkblade48 (Jan 4, 2008)

Acids (whether they be mineral acids or weak acids) will release their free hydrogen(s) when combined with carbonates. 

The process forms carbonic acid (carbon dioxide) as well as the corresponding salt.


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## KH2PO4 (Jul 18, 2009)

happi said:


> thank you, 0.2ppm of Kh per dose isn't bad at all.


That's not PPM, the 0.2 is dKH (German degree of carbonate hardness).
If you want PPM, it's 3.83985825623 PPM of CaCO3 equivalent.
(sorry for the long decimal but cutting it short will alter my previous and later results).

Calculating KH is a little more complicated. Because it's measured and 
communicated via CaCO3 equivalent.

1 dKH equals 17.848 PPM of CaCO3 equivalent.

So 0.21514221516 dKH is 3.83985825623 (let's say 3.84) PPM of CaCO3 equivalent.

Or in another word, adding 3 PPM of K from K2CO3 and you will 
also get about 2.3 PPM of CO3 from it. Which is equivalent to adding 
about 3.84 PPM of CaCO3, i.e., adding 3.84 mg of CaCO3 into 1 liter of 
water will increase CO3 by about 2.3 PPM.

API KH test kit reports in dKH (1 drop = 1 dKH).

K2CO3 is a base. So it can affect pH.



> in my solution mix i use ascorbic acid and potassium sorbate, will they react with the potassium carbonate??


I don't know


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## happi (Dec 18, 2009)

KH2PO4 said:


> That's not PPM, the 0.2 is dKH (German degree of carbonate hardness).
> If you want PPM, it's 3.83985825623 PPM of CaCO3 equivalent.
> (sorry for the long decimal but cutting it short will alter my previous and later results).
> 
> ...


my bad, yeh i meant to say 0.2 DKH, that mean adding 15ppm of Potassium will add 1 dkh.



Darkblade48 said:


> Acids (whether they be mineral acids or weak acids) will release their free hydrogen(s) when combined with carbonates.
> 
> The process forms carbonic acid (carbon dioxide) as well as the corresponding salt.


make since, do you know how much PH is altered by it?? i mean it doesn't go from 6 to 7 or does it??


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## Darkblade48 (Jan 4, 2008)

happi said:


> my bad, yeh i meant to say 0.2 DKH, that mean adding 15ppm of Potassium will add 1 dkh.
> 
> 
> 
> make since, do you know how much PH is altered by it?? i mean it doesn't go from 6 to 7 or does it??


If anything, the pH would decrease, not increase. How much it will decrease by, however, is hard to determine, as there are so many other factors at play.

I would not worry too much about the pH being affected, given the small amounts we are adding anyway.


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## happi (Dec 18, 2009)

Darkblade48 said:


> If anything, the pH would decrease, not increase. How much it will decrease by, however, is hard to determine, as there are so many other factors at play.
> 
> I would not worry too much about the pH being affected, given the small amounts we are adding anyway.



i thought carbonate suppose to increase the PH while increasing KH, the main reason and concern i have is that i am dosing NH4 and dont want the ph to go over 7 while dosing or after dosing the carbonate. i guess i will find out when i start dosing it. thanks to all for the help.


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## jfynyson (Apr 15, 2013)

pot carb as we call it is indeed an alkaline source (weak base). Works great in degreasers as a source for saponification !

It would likely be the strongest base in your tank though if added. If in excess it would for sure increase the pH. I believe in unbuffered systems it's pH is about 10ish. It will form a potassium salt with any free acids though and like one said you're using a very small amount in buffered system.


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