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:biggrin:

[dirtyreefer]

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.

[Beverly]

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

[hawaiiguy]

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.

[BMW Rider]

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:

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:

[Beverly]

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:

[BMW Rider]

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/forumdisplay.php?s=&forumid=112

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

[Ruth]

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:

[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: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)...

[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 :mrgreen:

Steve

[BMW Rider]

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)...

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:lol: :redface: 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:redface: 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:biggrin:

[EmilyB]

:lol: :lol: I usually leave experimentation to the experts. I'd never risk losing my tank occupants for a cheap solution....oh I think I've said this before...:razz: nevermind.

[Reef_kid]

check calcium hydroxide should be Ca(OH)2 you have calcium oxide down there and it at 95% ionization?? what are the % representing? mass?
its going to produce
Ca(OH)2 + H20 --- Ca2+ + H20 this is what you want!
but !! you have to realize that if you leave your kalc out it will react with CO2 in the air and will turn to CaCO3 and you dont want this because it ppt's out! its insoluble...

you dont actually have any magnesium hydroxide in there?
you may be thinking of magnesium oxide but this is such a small insignificant amount..

MgO + H20 ---> Mg(OH)2 milk of magnisum... solubility in H2O 0.0012 g in 100 g water

just do your stoick and see what the ratios come up with in comparison to your grams you use rather than teaspoon ect...
if the % is by mass.. you can calcualte the exact grams/mol or grams/l
and what the exact amount you will be putting in of each ,it looks like yoru not getting much magnesium out of this mix...
use a part per million conversion and again use stoic to see how much magnesium would be per gram... and look at avarage ppm in sea water that way you can see exactly how much you need to add. its kind of difficult to calculate with just average % of reactants.
hopefully your fish dont get diahrea from the milk of magnesium thtat is produced by the adition of MgO and H2O


sorry if i am not making sence ... to much chem today ... lab due tomorrow eheh...
cheers do some more research on the brand your using ..
i worrie about contamination of heavy metals and age.. due to the ppt of calcium carb ... if you notic a lot of settlement in the bottom of a jug of your solution .. its most likly the calcium carb.

[hawaiiguy]

Ahh labs... I've got a biochem lab due tomorrow too!! I know how it is:cry:

Anyways, I'll try working out the stoichiometry of the magnisium this weekend. Are you saying there could be too much magnesium in the mix? Does too much magnesium result in regular (as in diharea) fish?

[Reef_kid]

sorry the magnesium wont give the fish diareah i was joking milk of magnisum is a laxitive...

the type of magnessium that is in the mix you have
even if you added it to acid.. acetic .. the acid is going to be the limiting reactant! and because you dont know the molarity of the acid and you would have to have excess acid ... therefor your not going to get free Mg ions in the water
if you mix magneisum hyroxide with H2O ... it forms milk of magnesium which has a very low solubility...

the problem is that the mix seems to have a lot of CaCO3 which has a low solubility...

i still dont understand the % that you have down... since it adds up to over 100% ?... is there any other info given?

ask your chem teacher about it ?