question for all you chemists out there (Calcium Hydroxide)

[hawaiiguy]

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

 

[rayjay]

I don't know of anyone that "neutralizes" kalk with acetic acid, but rather use the vinegar to get more of the calcium to dissolve in order to boost calcium levels a little instead of just maintaining levels.
I use "hydrated lime" or calcium hydroxide as the bag is also labelled, from the farm co-op stores that sell it to the farmers for barn floor disinfectant, utilizing the high pH to do so.
Check Randy Holmes-Farley's forum for chemistry of it all. I believe he might actually be using Calcium Oxide instead of using calcium hydroxide.

 

[asterchem626]

Folks,

Acetic acid (vinegar) will protonate the hydroxide of Ca(OH)2 but leaves behind acetate. Acetate anion will complex to trace metals in your tanks. Acetate just doesn't taking care of nitrates, where is a reference for that?

 

[rayjay]

This thread is almost 5 yrs old!!