question for all you chemists out there (calcium hydroxide)

[Ruth]

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

I think the only thing I can say is HUH?

[hawaiiguy]

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 (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)...

[Buccaneer]

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

[hawaiiguy]

I got a big 20kg bag from Totem Building Supplies here in Lethbridge (it's like Home Depot). The brand is called Graymont (on the bag it says: High Calcium hydrated lime type "N")

[Buccaneer]

Thanks ... have you done any testing of your tank parameters before and after dosing ?

[StirCrazy]

I think what you are going to find is commercial lime often contains impurities, e.g., silica, iron, alumina, and magnesia. If you can find a bag that has a guarenteed analysis your ok.

the stuff you are looking at looks like a left over hog pog of chemicals.. one concern I have is that Calcium carbide reacts with water, releasing acetylene. could get a lottle flamable around the tank

Steve

[BMW Rider]

Originally Posted by hawaiiguy

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 (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)...

Good on ya. I'm more of a hardware DIY guy. I'll stick to commercial additive products and leave the chemical witchcraft to those who can. Its nice to have someone on the forum though that may be able to help some of us less informed types with chemistry problems.

[hawaiiguy]

Assuming there is calcium carbide in the mix, I suppose acetylene would form. It seems unlikely to be an issue though... just based on its structure CaC2 is likely unstable and hard to form; there's no way that free Ca ions would react with organics in the tank to form it. The only way it could get into the tank is if it's in the dry mix already and I doubt that very much. The formation of calcium carbide requires a pure carbon source and LOTS of heat (CaC2 is an alkyne which means it has a triple bond in it, the formation of which requires lots of energy).

Other impurities were my biggest concern when I first started looking into this... I'm hoping there isn't much else in this mix besides the ingredient list So far (after 12 hrs) everything is dandy! All I have right now is a long tipped anemone and it's as happy as a clam. An article by Randy Holmes-Farley reassured me a bit about impurities though. He says that lime will react with most other metals like copper and precipitate them out.

Water parameters are fine right now. pH is about 8.3, specific gravity is about 1.024, nitrates are near 0. Unfortunately I don't have a Ca test kit right now... that would be the most useful right now I'm going to try to pick one up soon.

[hawaiiguy]

All right, so it's been over 24 hours and everything is still as it should be... I think I have a good mix!

[hawaiiguy]

Oh yeah, one other thing: the bag I have is 20kg and I'll only be using about a teaspoon or two with each dose!!! Anyone want some? For those in Calgary, I head up there periodically. I'll also be posting a couple of tanks in the for sale section soon so if you buy those, you can take some lime with you too