Canreef Aquatics Bulletin Board - question for all you chemists out there (calcium hydroxide)

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question for all you chemists out there (calcium hydroxide)

Ok, I've read threads that describe the use of calcium hydroxide (usually neutralized with acetic acid). I'm a big fan of DIY so rather than by a calcium reactor, I like the idea of a homemade source of Ca(OH)2. I went to my local hardware store to check out their lime mix and here's the ingredient list:

Neutralizing value as CaCO3 eq, min (%): 131.51
Calcium (Ca), min (%): 51.88
Calcium Carbonate (CaCO3), max (%): 4.0
Calcium Hydroxide (CaO) min (%):95.9
Magnesium (Mg), min (%): 0.37
Magnesium Carbonate (MgCO3), min (%): 0.0
Magnesium Oxide (MgO), min (%): 0.62

Any problems here? Technically, what they call calcium hydroxide is actually calcium oxide but I think when it mixes with water it should get hydrated to Ca(OH)2.

CaO + H2O ---> Ca(OH)2

is that correct?

My concern is the reactivity of Magnesium hydroxide... I'm unsure of the chemistry here but I believe the MgO will hydrate to Mg(OH)2 just like the CaO above. Then, if I'm neutralizing it with vinegar the reaction should proceed like this:

Mg(OH)2 + 2 CH3COOH ---> Mg+2 (aq) + 2 CH3COO- (aq) + 2 H2O

This would be similar to the reactivityof calcium hydroxide right? Creating free magnisium ions would be a good thing right?

Anyways, If anyone has any insights about this ingredient list or the chemistry involved, I'd love to hear them:biggrin:

Dude, you lost me at Ca(OH)2 :)

Just kidding, however I have seen people use vinegar (the acetic acid you mentioned) being used to neutralize Kalk. You can buy Kalk as "pickling lime" which is I believe is only sold in the states in that form, however alot of people buy bulk Kalk all the time.

I think you can also use epsom salts for a source of Mg. You should check the Reef Chemistry forum on RC, Randy has some good homemade recipes to supplment Ca, Alk, pH, and Mg.

Wow! Someone who actually knows chemistry :biggrin: At least far, far, FAR better than I :smile:
While I'm not a big DIY-er, his link should point you in the right direction for DIY additives...

An Improved Do-it-Yourself Two-Part Calcium and Alkalinity Supplement System:

http://reefkeeping.com/issues/2006-02/rhf/index.php

thanks for the links... I think I'm going to go ahead and try the lime mix I have, I just need to figure out the stoichiometry here. Wish me luck:biggrin: I'll let everyone know how it goes.

Quote:

Originally Posted by hawaiiguy

Ummmm..... I'm sorry, I wasn't listening, can you repeat the question.... In english this time. :lol: :lol:

I can see that my retention of high school chemistry is about nil. :cry: :cry:

Quote:

Originally Posted by BMW Rider

I can see that my retention of high school chemistry is about nil. :cry: :cry:

At least you have high school chemistry :biggrin: I flunked out of Chem 10 :redface:

Quote:

Originally Posted by Beverly

At least you have high school chemistry :biggrin: I flunked out of Chem 10 :redface:

I did ok in Chem 30, but that was more than half a lifetime ago. Still, it was nowhere near this level.

I think a good place to ask this question is in the Chemistry forum at Reef Central.

http://reefcentral.com/forums/forumd...s=&forumid=112

You'll probably get a response that is at least helpfull there :redface:

Quote:

Originally Posted by hawaiiguy

Neutralizing value as CaCO3 eq, min (%): 131.51
Calcium (Ca), min (%): 51.88
Calcium Carbonate (CaCO3), max (%): 4.0
Calcium Hydroxide (CaO) min (%):95.9
Magnesium (Mg), min (%): 0.37
Magnesium Carbonate (MgCO3), min (%): 0.0
Magnesium Oxide (MgO), min (%): 0.62

Any problems here? Technically, what they call calcium hydroxide is actually calcium oxide but I think when it mixes with water it should get hydrated to Ca(OH)2.

CaO + H2O ---> Ca(OH)2

is that correct?

My concern is the reactivity of Magnesium hydroxide... I'm unsure of the chemistry here but I believe the MgO will hydrate to Mg(OH)2 just like the CaO above. Then, if I'm neutralizing it with vinegar the reaction should proceed like this:

Mg(OH)2 + 2 CH3COOH ---> Mg+2 (aq) + 2 CH3COO- (aq) + 2 H2O

This would be similar to the reactivityof calcium hydroxide right? Creating free magnisium ions would be a good thing right?

Anyways, If anyone has any insights about this ingredient list or the chemistry involved, I'd love to hear them:biggrin:

I think the only thing I can say is HUH?:silly:

I guess my excuse is that I'm finishing my biology undergrad right now and I've gone pretty heavy on the chemistry for the past 4 years:wink: (I could probably minor in it; haven't really checked) It's still fresh in my mind (shudder...)

I have been doing some reading at reefcentral and reefs.org and I've decided the mix I have is safe... I just dosed my tank with about 10mL of the stuff so we'll see what happens (so far, so good)...

So what hardware store and what is the brand of lime-mix you are using ?