Question about Kalkwasser and Vinegar

[Wrasse-cal]

I can't find an answer to these exact questions:

I understand adding vinegar to kalkwasser will allow more Calcium ions into the solution, which will increase the Calcium saturation of the solution, meaning less saturated kalkwasser is needed to maintain Calcium.

1. Is there a sizable effect on kalkwasser pH when adding vinegar? I frankly like the pH raising effect of kalkwasser. How significant is the pH drop when dosing 25ml of 5% Acetic Acid per liter of saturated kalkwasser?

2. I understand about the increased Calcium ion saturation, when adding vinegar, but what effect does dosing vinegar have on the KH of the kalkwasser? Does it also increase it proportionally to the Calcium?

 

[Dan_P]

I can't find an answer to these exact questions:

I understand adding vinegar to kalkwasser will allow more Calcium ions into the solution, which will increase the Calcium saturation of the solution, meaning less saturated kalkwasser is needed to maintain Calcium.

1. Is there a sizable effect on kalkwasser pH when adding vinegar? I frankly like the pH raising effect of kalkwasser. How significant is the pH drop when dosing 25ml of 5% Acetic Acid per liter of saturated kalkwasser?

2. I understand about the increased Calcium ion saturation, when adding vinegar, but what effect does dosing vinegar have on the KH of the kalkwasser? Does it also increase it proportionally to the Calcium?

Is the kalkwasser clear, free of solids?

 

[Wrasse-cal]

Is the kalkwasser clear, free of solids?

Yes.

I dose from a reservoir, with undissolved kalk powder on the bottom, so it should be fully saturated. I stir it when I refill it, wait until it turns clear, then use it.

 

[Dan_P]

Yes.

I dose from a reservoir, with undissolved kalk powder on the bottom, so it should be fully saturated. I stir it when I refill it, wait until it turns clear, then use it.

The answer to your questions then depends on how much solid kalkwasser do you intend to be around when you add vinegar. I can given you information for clear kalkwasser solutions with no solids.

 

[theMeat]

Why are you looking to add vinegar to kalk?

Is fully saturated solution not enough in terms of supplementing Enough calcium?

 

[Wrasse-cal]

Why are you looking to add vinegar to kalk?

Is fully saturated solution not enough in terms of supplementing Enough calcium?

My daily kalkwasser dosing is at my daily evaporation amount. It is not keeping up with my KH consumption.

 

[theMeat]

How much kalk per gal are you adding?

 

[Wrasse-cal]

How much kalk per gal are you adding?

I'm fully saturated. I add double the amount of kalk I should need per gallon, and have undissolved kalk at the bottom.

 

[theMeat]

What’s your cal and alk levels?

 

[Mastiffsrule]

Here it is straight from the master, has a section vinegar and limewater

http://reefkeeping.com/issues/2005-01/rhf/index.htm#17

 

[Wrasse-cal]

8.5-8.6
443

 

[JimWelsh]

Vinegar to kalkwasser ratio

Using the guidance that @Randy Holmes-Farley gave us here, I calculate that saturated limewater at 25C has a pH of 12.556 ([OH-] = 0.036; -log(0.036) = pOH of 1.444; pH = 14.0 - 1.444 = 12.556). Acetic acid has a MW of 60.052, so a 5% w/v solution will be 50/60.062 = 0.833 M. The 25 mL you are adding will contain 0.833 * 25 / 1000 = 0.0208 moles. Since acetic acid has a pKa of 4.76, then at a pH north of 12, it will effectively be 100% dissociated, so [OH-] becomes 0.036 - 0.0208 = 0.0152, and the pH becomes 12.182 (-log(0.0152) = pOH of 1.818; pH = 14.0 - 1.818 = 12.182).

I'll let @Dan_P calculate how much the pH goes back up once the additional Ca(OH)2 goes into solution!

 

[Wrasse-cal]

Here it is straight from the master, has a section vinegar and limewater

http://reefkeeping.com/issues/2005-01/rhf/index.htm#17

Thanks, but that article (it's a good one, I've seen it before) doesn't directly answer my questions. If it does, I missed it.

 

[Wrasse-cal]

Vinegar to kalkwasser ratio

Using the guidance that @Randy Holmes-Farley gave us here, I calculate that saturated limewater at 20C has a pH of 12.556 ([OH-] = 0.036; -log(0.036) = pOH of 1.444; pH = 14.0 - 1.444 = 12.556). Acetic acid has a MW of 60.052, so a 5% w/v solution will be 50/60.062 = 0.833 M. The 25 mL you are adding will contain 0.833 * 25 / 1000 = 0.0208 moles. Since acetic acid has a pKa of 4.76, then at a pH north of 12, it will effectively be 100% dissociated, so [OH-] becomes 0.036 - 0.0208 = 0.0152, and the pH becomes 12.182 (-log(0.0152) = pOH of 1.818; pH = 14.0 - 1.818 = 12.182).

I'll let @Dan_P calculate how much the pH goes back up once the additional Ca(OH)2 goes into solution!

Thanks. My other main question can be summarized as follows: kalkwasser is commonly described as a balanced additive, meaning dosing to keep alkalinity stable will also keep Calcium stable. I assume this would be the case even when if vinegar is added to the kalkwasser--but I want to make sure I'm right about that.

 

[dwest]

8.5-8.6
443

You’ll also be carbon dosing if you add vinegar. That’s the only reason I haven’t done it.

 

[Wrasse-cal]

You’ll also be carbon dosing if you add vinegar. That’s the only reason I haven’t done it.

Yeah. I was considering trying carbon dosing out, but I'm not thrilled about doing it in an uncontrolled way versus a stable, daily dose dosed separately.

Right now, I'm trying out a small dose of nopox--1 ml per day.

 

[Ebslinger]

Forgive me, but I can't help but think that if you have to start adding vinegar to your Kalk, it might be time to switch to 2 part...

I know it is off topic.

 

[Wrasse-cal]

Forgive me, but I can't help but think that if you have to start adding vinegar to your Kalk, it might be time to switch to 2 part...

I know it is off topic.

No worries. If I truly am at capacity, my plan is to restart my CA reactor.

 

[dwest]

Thanks. My other main question can be summarized as follows: kalkwasser is commonly described as a balanced additive, meaning dosing to keep alkalinity stable will also keep Calcium stable. I assume this would be the case even when if vinegar is added to the kalkwasser--but I want to make sure I'm right about that.

I believe the balance will still be there. But honestly, you could try and test it as you go. I will be in the same situation soon. I plan to dose 2 part at that point as I’ve done that before successfully.

 

[theMeat]

8.5-8.6
443

Ok, one last question. What’s your ph?

Oh wait. Your alkaline is 8.5-8.6? Or is that your ph?