99.5% acetic acid with calcium

[eli@fijireefrock.com]

i am not much of a chemist
a couple of days ago i bought acetic acid 99.5%, calcium carbonate 98.5% USP grade and kalkwasser and my oolitic sand from my reef tank.

in 3 different cups i added a 1tsp of each of the calcium product above
and 1tsp of the acidic acid into each cop

few hrs later

calcium carbonate no changes :confused:
kalkwasser all desolved with enough acid to dessolve more :biggrin:
reef sand desolved with enough acid to dessolve more :biggrin:

why did the calcium carbonate not dessolve :question: :confused:

[eli@fijireefrock.com]

:smilecol:
:idea:
:question:

[Aquattro]

why did the calcium carbonate not dessolve :question: :confused:

You'll need to look up the solubility constant (Ksp) of CaCO3 and compare it to the values of the other substances. You'll likely find it's much higher, thus less soluble.

[Aquattro]

Here is a table...

http://www.ktf-split.hr/periodni/en/abc/kpt.html

appears that a couple of compounds are listed for CaCO3, calcite and aragonite. You'll need to determine the species you have. Also, physical state (rock, powder, etc) can play a role.
Based on the table though, I'd expect similar results from calcite and aragonite, assuming both were powders.

[eli@fijireefrock.com]

it is in powder form
certificate of analysis

acid insoluble substance.....................................0.03 %
magnesium and alkali salts.................................0.50%
heavy metals............................................ ........0.0005%
CaCo3............................................. .................98.7% to 100.5%


shouldn t calcium carbonate start to dessolve in a liquid sustance that at low ph

[Aquattro]

shouldn t calcium carbonate start to dessolve in a liquid sustance that at low ph

Well, you'd think it would...

Maybe this explaind it..

"Acetic acid is classified as a weak acid, because it does not completely dissociate into its component ions when dissolved in aqueous solution. At a concentration of 0.1 M, only about 1% of the molecules are ionized. In solution, there is a dynamic equilibrium between the neutral molecules and the acetate and hydronium ions."

What this tells us (if my chemistry is intact) is that in aqueous solution, this weak acid only contibutes modestly to the overall [H+] and therefore does not react strongly with the CaCO3. You may see a proportionaltely greater amount of dissolution if you do not mix the acid with water. Be aware though, that acetic acid can burn your skin and appropriate precautions should be taken before testing this :biggrin:

Disclaimer: It's been some time since chem class :razz:

[eli@fijireefrock.com]

i have tried usind acidic acid no water and the rest still no dissolution to CaCO3
all this is to have more calcium into my reef
well how about acidic acid and reef sand would that not be almost the same end result as using calcium reactor

[Aquattro]

Why go thru all that trouble? Just use kalk in your make up water. Someone in Calgary has it real cheap, I recall, so that is what I think would be easiest.
To dissolve CaCO3 in a concentrated acid solution and adding it to the tank is asking for trouble, IMO.

[eli@fijireefrock.com]

late last night i gave up and was in the process of throwing the cups in the sink with water to wash away.

some water got into the cup that contains CaCo3 and acidic acid and gess what it was foaming and fising like crasy.
so i retested the method water CaCo3 powder acidic acid and it worked

my next step is to check the ratio of CaCo3 water to acidic acid and have a clear solution with a Ph of near reef water levels to go into my reef

[eli@fijireefrock.com]

late last night i gave up and was in the process of throwing the cups in the sink with water to wash away. :neutral:

some water got into the cup that contains CaCo3 and acidic acid and gess what :eek: it was foaming and fising like crasy. :onfire:
so i retested the method water CaCo3 powder acidic acid and it worked

my next step is to check the ratio of CaCo3 water to acidic acid and have a clear solution with a Ph of near reef water levels to go into my reef

[Aquattro]

my question again is why? what about alk? CaOH offers a balanced solution that's easy to use and costs very little.

[eli@fijireefrock.com]

correct me if i am wrong
deluted CaCo3 in acidic acid comes back as CaCo3 in the reef
the price and grade of the CaCo3 USP grade is better than kalkwasser with its metal sediments

[Aquattro]

correct me if i am wrong

I have no idea. Maybe you're wrong, maybe you're right. But locally I buy kalk for about $5 per large bag. This bag lasts me around 6-8 months. So let's call it $10/year. I then mix it with water, and I know water is safe for my tank in the amount I need to dissolve the kalk in. Now I can't say the sae for vinegar. I use vinegar with kalk, around 80ml. This seems safe. It's a documented process, condoned by chemists.
Did I mention $10/yr?
At the very least, I would run it by Randy over at RC. He can tell you if you're right or wrong, and offer solutions to your questions. Just seems like a lot of work to do something that isn't a lot of work. Know what I mean?