Testing RowaKalk

[Boomer]

I don't know how you came up with that

I mean that if the skim on top of the kalkwasser forms from CO2 in the air

It does't form from the CO2 in the air, CO2 will keep it in solution, it is from CO2 leaving the surface or water. Think of the waters edge in your tank and the CaCO3 deposites on the water air interface. Adding CO2 will not make it precip, unless you loose that CO2 first. If precip happens it is bacasue there was not enough CO2 in the first place in the Kalk, if you then added more CO2 it would not precip.

then adding CO2 (from the air) causes precipitation because there wasn't enough CO2 in the first place.

This should more or less read

The adding more Ca(OH)2 casues precipitation because there wasn't enough CO2 in the first place.

Go back and readed that first link I gave

Your statemnt or where ever you got they from makes no sense, so it should be confusing

 

[dnjan]

I see where I got confused. For normal kalkwasser (no vinegar), there is very little CO2 in the water, and any additional CO2 (from the air) makes the precipitate on the top of the water.

With the correct amount of vinegar, you have calcium bicarbonate, not calcium hydroxide, in the kalkwasser bucket.

I was thinking of normal kalkwasser, not kalk plus vinegar.

So, now, another question - when you add normal kalkwasser to the tank, you are essentially taking bicarbonate from the tankwater to make calcium bicarbonate. But when you add vinegar-spiked kalkwasser, you are not taking bicarbonate from the tankwater. Regular kalkwasser is referred to as a "balanced" additive. Is spiked kalkwasser also "balanced"?

 

[wrightme43]

I may have it wrong but my understanding is that it is a lack of available co2 that causes it. It is also my understanding that a small amount of vinager fixes it so that it is available for the corals to use vs. locked up and unavailable. Like I said I may be wrong, that is just how I understand it.

 

[Boomer]

Don


I see where I got confused. For normal kalkwasser (no vinegar), there is very little CO2 in the water, and any additional CO2 (from the air) makes the precipitate on the top of the water.

No

When you put kalk in the water this happens

Ca(OH)2 {kalk} reacts with any CO2 in the water or we will say any CO2 coming in from the air into the water. The CO2, from the air or water, combines with the OH from the kalk and forms HCO3 (bicarbonate)and Ca. As the pH rises the HCO3 will lose the H and you will have CO3. If there is not enough or no CO2 in the water or air left, the CO3 will react with the Ca and form CaCO3. If there is enough CO2 the CaCO3 will not form, as CO2 acts as an acid and keeps CaCO3 from forming.


With the correct amount of vinegar, you have calcium bicarbonate, not calcium hydroxide, in the kalkwasser bucket

Yes, and no When the kalk is in the water, it is no longer kalk as the Ca leaves the (OH)2, so you now have Ca & OH. It goes into solution just like table salt The OH, as I said above, combines with the CO2 and you now get Calcium & bicarbonate

The right amount of vinegar, is the same as the right amount of CO2. The vinegar is releasing CO2. Normally there is not enough CO2 in the water, so one adds vinegar, Vodka or injects the water with CO2, so more of the Ca(OH)2 goes into solution and there is thus little precip of Calcium carbonate Ca(CO3). If there is not enough of the that CO2 you will then get Ca(CO3). The precip forms when there is no acid or little to keep it dissolved then the precip comes.

Think of it this way Don. CO2 is an acid. If there is enough acid there will be no film/particles/precip of Ca(OH)2 or CaCO3, as an acid dissolves them. It takes more acid to dissolves kalk than CaCO3. It the acid (CO2) leaves the water, say to the air, there is nothing in the water to keep it dissolved so CaCO3 forms.

So, now, another question - when you add normal kalkwasser to the tank, you are essentially taking bicarbonate from the tankwater to make calcium bicarbonate. But when you add vinegar-spiked kalkwasser, you are not taking bicarbonate from the tankwater. .

No, just to repeat the above. Adding kalk MAKES bicarbonate. CO2 + OH = HCO3 . If you add CO2 it allows you to MAKE more HCO3, as all the kalk you add may not ALL dissolve. The addition of more CO2 will now dissolve all of it. It you do not add enough CO2 it will run out of CO2 and CaCO3 will from

Regular kalkwasser is referred to as a "balanced" additive

It is called balanced because you are adding an equal amount of Ca and Alk to the water. Think of it as 1 part of each or 1 to 1. If it was 4 to 1 it would not be balanced

Finally, lets take this apart

For normal kalkwasser (no vinegar), there is very little CO2 in the water, Yes, that is correct and a precip will/may occur.

and any additional CO2 (from the air) makes the precipitate on the top of the water

1. No, if there is enough CO2 always.

2. Yes, if there is enough or all most enough CO2 and then you loose the CO2, ie., it escapes back to the air, it gets eaten up by reactions, what ever they are. Since you have lost the CO2 the CaCO3 forms

 

[dnjan]

Ca(OH)2 {kalk} reacts with any CO2 in the water or we will say any CO2 coming in from the air into the water. The CO2, from the air or water, combines with the OH from the kalk and forms HCO3 (bicarbonate)and Ca. As the pH rises the HCO3 will lose the H and you will have CO3. If there is not enough or no CO2 in the water or air left, the CO3 will react with the Ca and form CaCO3. If there is enough CO2 the CaCO3 will not form, as CO2 acts as an acid and keeps CaCO3 from forming.

When I mix kalk, there is practically no CO2 in the water (I know that some areas using groundwater can have fairly high disolved CO2, but our water here comes from surface supplies, not groundwater). If I leave the kalkwater stand for a few days, a skin forms on the surface. This is in agreement with the first article you posted the link to. Since the pH of the kalkwasser is high (excess calcium hydroxide added), the solubility of calcium carbonate is lower than the solubility of calcium hydroxide.

So, now, another question - when you add normal kalkwasser to the tank, you are essentially taking bicarbonate from the tankwater to make calcium bicarbonate. But when you add vinegar-spiked kalkwasser, you are not taking bicarbonate from the tankwater.

No, just to repeat the above. Adding kalk MAKES bicarbonate. CO2 + OH = HCO3 . If you add CO2 it allows you to MAKE more HCO3, as all the kalk you add may not ALL dissolve. The addition of more CO2 will now dissolve all of it. It you do not add enough CO2 it will run out of CO2 and CaCO3 will from

Here is where I get lost. When I add saturated calcium hydroxide to the tank, is there an efect on the carbonate - bicarbonate balance in order to avoid excessive pH from the hydroxide ion in the saturated calcium hydroxide? It seems like disolved CO2 from the tank is required to keep the bicarbonate content up (hence the caution against adding kalkwasser too quickly). So adding kalkwasser reduced the disolved CO2 content. Seems like a good thing, within reason.

But when adding saturated calcium acetate (vinegar-spiked kalkwasser), there is no CO2 reduction, correct? Is that the reason why you should watch your pH when you switch over to spiked kalkwasser (if you aren't removing some of the CO2, the pH would gradually drop, correct?)

Hate Chemistry! A necessary Evil, but I still hate it. So there is probably some deep father-son issue here in why my son is considering majoring in chemistry in college.

 

[Boomer]

there is practically no CO2 in the water

How do you know that . CO2 is a function of pH and Alk, to include salinity and temp. Give me those and I can tell you how much CO2 there is


When I add saturated calcium hydroxide to the tank, is there an efect on the carbonate - bicarbonate balance

The ratio of bicarb to carb is a function of pH....PERIOD, but salinty and temp also will change the ratio slightly. So, if your temp was always 82 F and the sainlity was always 35 ppt, then only a shift in pH will change the ratio. As pH rises there will be a higher % of carb than bicrab and as the pH drops there will be a higher % of bicarb than carb. I should add that CO2 is also in there, as it really is a ratio of CO2-bicrab-carb, so at higher pH's there is very low % of CO2 and at lower pH there is a higher % of CO2. In seawater at a pH of just over 9 it is almost 50 % bicarb and 50 % carb, with a tad of CO2. At a pH of 6 it is almost 50 % CO2 and 50 % bicarb, with a tad of carb.

Note; Do not confuse % with concentration. 1 apple and 1 orange is 50-50 % and 10 apples and 10 oranges is still 50-50 %.

But when adding saturated calcium acetate (vinegar-spiked kalkwasser), there is no CO2 reduction, correct? Is that the reason why you should watch your pH when you switch over to spiked kalkwasser (if you aren't removing some of the CO2, the pH would gradually drop, correct?)

Yes, more or less. You are now entering a area I don't think you want to get into. I'll give one example.

pH = 8.3, with a high Alk and a high CO2

pH = 8.3, with a low Alk and a low CO2

pH = 8.3, with a moderate Alk and moderate CO2

my son is considering majoring in chemistry in college.
02-11-2005 11:17 PM

So in the future he will be able to fix you right up

 

[dnjan]

I think you misunderstood the first part - I was talking about my RO water. So salinity and alk would be zero, and the last time I checked the pH was pretty close to 7. Hence my assumption of no CO2 when I mix kalkwasser.

Yes, more or less. You are now entering a area I don't think you want to get into. I'll give one example.

pH = 8.3, with a high Alk and a high CO2

pH = 8.3, with a low Alk and a low CO2

pH = 8.3, with a moderate Alk and moderate CO2

So the effect of spiked kalkwasser on short-term pH depends upon which of the above three conditions exist?

Thanks Boomer for your patience.

 

[Boomer]

I think you misunderstood the first part - I was talking about my RO water. So salinity and alk would be zero, and the last time I checked the pH was pretty close to 7. Hence my assumption of no CO2 when I mix kalkwasser

No, misunderstanding. When you strip water of its Alk and all other ions, the RO/DO or RO water has no CO2. As soon as you expose it to air the CO2 will rise in the RO water and lower the pH. You also can't measure the pH of RO and especially RO/DI water, with a test kit or meter as it will give false results, as it has been striped of all its ions. So, such pH readings are meaningless.

the above three conditions exist ?

None of the above, I was trying to make a different point, as to if the CO2 and Alk are balanced, no mater what the concentration, the pH can be the same. The short term will depend on how much CO2 there is or isn't. As CO2 increases, no matter what the alk, the pH will drop, unless the Alk rises in proportion to the CO2

 

[wrightme43]

O.K. I am trying very hard to follow this. I have been watching and reading and reading and reading and thinking and reading the same thing again. Here is the gist I get. Again, through incredible luck and not intellegence I am doing the right thing by adding vinager to my kalk wasser. LOL I sorta thought I knew why I was doing it. Now I have a better understanding of why it works. LOL Thanks Boomer. If I am wrong please feel free to tell me. I would rather get better than keep doing the wrong thing over and over. Steve

 

[ROWAUSA]

well, I now know where to look if I ever have a question on Kalkwasser. Thanks again Steve.

 

[Boomer]

Glad to have helped

Wright

There is nothing wrong with adding vinegar or Vodka or using Calcium oxide instead of calcium hydroxide. For all practilce purposes, don't repeat this, as soon as calcium oxide "hits" the water it is "converted" to "calcium hydroxide" You just need to me more cautious with it as it is exothermic, i.e generates heat.