Proposed new lime purchase

[reefnroll]

Darren -

Calcium hydroxide still gets warm when mixed with water, but not HOT like oxide. Sure... I guess you can mix it using the 'dump in a bunch' method, but I think measuring is better for a varietly of reasons... preventing waste being one. You really just need to measure one time, then use the same amount for your container every time thereafter. From what I have understood from Greg, using more than you need means the excess will not go into soulution (be dissolved), but may go into solution when you refill the bucket with RO/DI the next time... but there's never any way to tell how much... and you never know how much more you need to 'dump' to make sure your water is completely saturated. If you measure once - knowing what you're adding is bringing the pH to the proper level, you don't have to wing it, and potentially waste a bunch of product... or have your topoff pH drop over time without realizing.

I'm making RO/DI tonight, and will mix up 5 gallons of limewater using this new batch of Calcium hydroxide tomorrow. I'll post what I find for anyone who is interested. If anyone else has already done this, please share!

Thanks,

b

 

[seasno]

Bec and All

I experimented a bit with the new lime tonight, and my results are as follows:

PH Meter = Oakton PH Tester Range of -1.0 to 15.0 +- .01 Calibrated before the test using Cal solution 7.0
Sample = 1 gal of RODI water TDS 4
Starting PH of RODI water = 6.3

I added Calcium Hydroxide in 1/4 tsp. increments, stirred vigoriously and tested with PH meter after each 1/4 tsp. addition. After 2 1/4 tsp. I reached a PH of 12.5, I continued to add an additional 2 tsp. in 1/4 tsp. increments and my PH reading didn't climb above the 12.5 level.

Conclusion: Using my RODI water and my PH tester.....Even though I didn't achieve a PH of 12.8, I feel using my meter I reached a saturation point (PH 12.5) after adding 2 1/4 tsp. of Calcium hydroxide to 1 gallon of RODI water which would equal 11.25 tsp. per 5 gallons. 1 cup equals 48 tsp. so Bec's guess of just shy of 1/4 cup ( 12 tsp.) per 5 gallons looks to be right on the money.

These results are posted for informational purposes...your results may vary due to differences in water samples and test equipment.

HTH,

Craig

 

[conrad]

From what I have understood from Greg, using more than you need means the excess will not go into soulution (be dissolved), but may go into solution when you refill the bucket with RO/DI the next time... but there's never any way to tell how much... and you never know how much more you need to 'dump' to make sure your water is completely saturated. If you measure once - knowing what you're adding is bringing the pH to the proper level, you don't have to wing it, and potentially waste a bunch of product... or have your topoff pH drop over time without realizing.

OK, I'm confused. Isn't stuff remaining undisolved pretty much the definition of saturated? If there's residue at the bottom, the solution must be saturated, right? I've been doing exactly what One Eye described, and assumed this was giving me a saturated solution with no waste. (If you don't dump the residue when you make the next batch, there is never any waste.) The other advantage of this technique of course is that you never have to measure anything.

I've read a bunch of articles on preparing and storing KW and have found all sorts of confusing and contradictory advice. But I had read something recently which seemed pretty definitive, and seemed to be advocating what One Eye described. Of course now I can't find the article to link it here. Anyway, I am desperately in need of a clue, please help!

--cn

 

[Shallowwaters]

Thanks Craig! This will shortcut the process for me. I have to mix 45 gallons of make-up water today and will post any contradictory results.

 

[One Eye]

Conrad, I don't ever mix a specific amount of top off. I have a 30 gallon RubberMaid bin that I drilled bulkheads in and use Kent floats in my sumps. When the RODI level starts to get low I turn on the RODI unit and let it fill up...I have another Kent float to auto shut off the RODI (in case I fall asleep again) I keep a powerhead in the resovoir to keep things mixed up. When I notice that there's not much residue on the bottom of the container I add more calcium. I've heard rumors that another reefer uses a 55 gal drum and a boat orr to mix things up.

 

[reefnroll]

Craig -
No need for me to be repetetive... so I'll just say that what I found today duplicated your results (and my early guess... woo hoo!). The amount needed to reach saturation also suggests that this is not the higher grade of Calcium hydroxide, but somewhere closer to the middle-lower of the range of possibilites Mark posted on the last page. It's basically half the strength of the calcium Oxide I'm using now... for the record.

conrad -
There's no confusion, and no definitive answer to how this process can work. I started my response to Darren with the following statement "Sure... I guess you can mix it using the 'dump in a bunch' method, but I think measuring is better for a varietly of reasons..." Emphasis on "I think." If you're happy with your method, then by all means, carry on. I prefer to know exactly how much product is going in, and what the pH is of the water coming out... immediately after mixing, and over time. In my experience (my experience) if I don't know how much 'leftover' product is going into solution every time I add water and re-mix mix, then I have no idea whether the pH of my tapoff is 12.8 or 10.8. I don't want to have to worry about that, so measuring once and using that same amount every time takes away the guessing game. For me... it's that simple, but I'm not saying it's the only way. I didn't post my method to be contradictory or to start a debate... it was informational only in response to Darren's question.

Darren -
I have found that no matter how accurate the measurement is... there is always some Calcium hydroxide/oxide that doesn't go into solution, leaving a residue on the bottom. Be careful about using the presence (or not) of residue as an indicator because it might not be the best sign of whether your water is fully saturated. But again... if that method is giving you double-time growth on all your torts... then you go boy.

Mark -
Let us know what you find.

b

 

[conrad]

Thanks for the explanations Darren and Bec! I'm not trying to challenge anyone or debate anything. I'm just a confused n00b trying to understand things. I guess knowing a bunch of things that work is great, but I really want to understand how and why things work too.

So my confusion was that I didn't understand how your solution could be anything but saturated at 12.8 or whatever the pH of saturated KW is if you had residue at the bottom (by definition of saturation). It seemed irrelevant and very possibly error prone to attempt to measure it (though I just got a pH monitor today and now see that there does seem to be a good way of measuring pH).

I very much understand Bec's desire to find a formula for this particular stuff -- you plop so many scoops into your certain sized container and you know where you stand. That's what I was doing originally, but then read a bunch more things and read about someone doing it the way Darren describes and that sounded even simpler (especially if you don't have enough RO/DI to fill your KW container to the usual level) and doesn't waste anything since you recycle the residue.

It sounds like the key part I was missing is the part in Bec's caution to Darren. Bec, you're saying that you can have residue in KW when the solution is less than saturated? Can someone explain that to me? It doesn't fit with what little I recollect from high school chemistry long, long ago.

I hope people around here don't think I'm an annoying PITA who likes to argue about things. I'm not comfortable when I don't understand things, so I keep asking questions even after most others are satisfied. I've been working a long time with some ultra precise professors and grad students, and teaching inquisitive undergrads, and don't like it when my imperfect understanding of something hangs me out to dry.

--cn

 

[reefnroll]

Hey conrad -

No problem asking questions. We're all learning from and with each other here.

I agree with your memory of high school chemistry... and can only guess that one reason there could be residue along with complete saturation (while measuring properl)y is that there is probably something other than pure Calcium hydroxide/oxide in the product that's not completely breaking down in water. Maybe that's the difference between the various grades... the purity of the product.

Having a 'recipe' for folks (and myself) seems like the safest bet, at least to start. If people become more experienced and feel comfortable just dumping... that's o.k. too.

b

 

[Moe_K]

When making kalkwasser, I want to just add 1 tblspoon per gallon of RODI water, mix and let settle. That should work, right?

 

[conrad]

Ah, cool, thanks Bec, it makes sense I guess if the powder is impure.

Just to be precise though, the thing that was puzzling me was residue along with incomplete saturation. (I realize you probably just made a typo.) In other words, if you add slowly, mixing it as you go, does an insoluble residue start to form before saturation at 12.8 pH or whatever? I may do an experiment when I have to make my next batch.

Again, many thanks for the info, I think it's making more sense to me now!

--cn

 

[seasno]

When making kalkwasser, I want to just add 1 tblspoon per gallon of RODI water, mix and let settle. That should work, right?

Moe....technically 3/4 of a tablespoon would get you to saturation point....but I don't think the extra 1/4 tablespoon is going to cause any huge issue.

 

[Mike A]

So what types of containers are you folks using to store the large quantities of the calcium hydroxide powder ?

Should I just throw it in a 5 gallon pail with a cover ?

 

[reefnroll]

Hey Mike -

Yeah... an IO bucket - the extra tall ones - will do it for sure. I've had my Oxide in one since the last group buy. Maybe even a regular 5 gallon bucket will do. Just make sure you've got the rubber gasket inside the cover to keep it as air-tight as possible.

conrad -
That wasn't a typo. There indeed may be some risidual sinking to the bottom even though the water is not fully saturated to 12.5 or 12.8 or whatever... That risidual would be the impurities in the product (if my theory about what exactly that is is accurate). It's hard to say how much is sinking and when. My water turns pretty cloudy when I'm mixing, so we're talking about particles AS they dissolve. I can't tell at that point what's dissolving and what's sinking. What I can tell you is that I can never remember a time when there wasn't some powder at the bottom... no matter how precisely I mesaured and how long I mixed.

I believe that if 3/4 teaspoon per gallon (of this particular product) brings water to saturation, then some small percentage of that 3/4 teaspoon will not dissolve, and will never dissolve in subsequent mixings because it is 'impure' (for lack of a better term).

b

 

[Greg Hiller]

>I've heard rumors that another reefer uses a 55 gal drum and a boat orr to mix things up.<

Hmmmm....that would be me. However, I do ball park measure it when I dump it in each time I top off my kalkwasser bucket with fresh DI water.

>I have found that no matter how accurate the measurement is... there is always some Calcium hydroxide/oxide that doesn't go into solution<

The solubility of calcium hydroxide/oxide (remember once the oxide hits the water it is hydroxide) is dependent partially upon temperature. As it turns out, calcium hydroxide is MORE soluble at low temp than at high temp (contrary to most solids which usually dissolve more fully at warm temps). While I cannot comment on Moe's latest batch, I don't think there is likely to be a lot of impurities in the calcium hydroxide. Also, the very low pH of the solution when you prepare it tends to make it 'self purify'....bad stuff falls out of solution. Randy has some articles talking about this.

Keep in mind also, that there is going to be some dissolved carbon dioxide in the water you are mixing it into. That CO2 reacts with the calcium hydroxide to form insoluble calcium carbonate (same thing your corals do in your tank). The insoluble calcium carbonate falls to the bottom of the container. Even if you keep adding water again and again to your kalkwasser reservior (without adding anymore calcium hydroxide powder), this insoluble calcium carbonate will not go into solution unless you lower the pH of the water significantly. This reaction with carbon dioxide also occurs on the surface of the water reservior as carbon dioxide diffuses into the water and reacts. You can end up with a 'scum' or crust layer on the top of the water. Most people keep the reservior covered to limit this diffusion and reaction. The reaction is not a big deal though; Randy ran a simple experiment a while back to suggest that over a several week period with a covered unmixed container of kalkwasser (mixed initially upon addition of the powder), the container remains essentially saturated the entire period of time. This is why I just dump it into a big bucket, mix it with a canoe paddle and use it until it's gone.

I'll post it again because there still seems to be some confusion on the point:

From the OLD info/thread(s):

>you should be aware that calcium oxide is slightly more potent. CaO has a MW of 40+16=56, Ca(OH)2 is 56+18 (one molecule of water)=74. So, by a wt. percent basis, CaO is 71.4% calcium, whereas Ca(OH)2 is 54% calcium. So, on a weight basis you would use 24% less of CaO than you were using of Ca(OH)2 (I don't know how dense the two powders are, so weight is the best way to measure the stuff, BTW). <

One a WEIGHT basis, which is how you all are paying for the material, the calcium oxide that we purchased in the past is 71.4% calcium, the calcium hydroxide you just purchased HERE (assuming that is what you purchased) is 54% calcium. THEREFORE if you were using 100 grams of calcium oxide (for whatever volume of water you were using), you would need 131 grams of calcium hydroxide to end up with the same amount of calcium in the water. 31% more. This is based on the WEIGHT. Calcium oxide might be more dense (I don't know/don't recall), so on a volume basis it might be different.

 

[conrad]

OK, thanks for the clarification, Bec. I'm going to do an experiment when I mix up my next batch, now that I have a pH meter. I did check mine this morning when I was adding my topoff, and my KW was at 12.25 pH, so my crude method of preparing this stuff may not make a fully saturated solution, and may not be consistent. I think I probably don't even want a fully saturated solution though, after watching the pH monitor as I added my topoff. My systems are very small (5.5 and 29), so I think I'm pushing it with rising pH shock. I need to either detune my KW solution or go back to dripping rather than just dumping for topoff.

This discussion is really helping, thanks for bearing with me!

--cn

 

[conrad]

Randy ran a simple experiment a while back to suggest that over a several week period with a covered unmixed container of kalkwasser (mixed initially upon addition of the powder), the container remains essentially saturated the entire period of time.

That's the article that I read recently which prompted me to switch to the simple method of dumping some very rough guess on top of the old residue when making a new batch. Can anyone come up with a link to that article? I was unable to find it when I hunted for it again the other day.

This is why I just dump it into a big bucket, mix it with a canoe paddle and use it until it's gone.

Greg, what do you do when it's gone, do you dump the old residue and rinse out your bucket, or just dump the new in on top of the old? I do the latter, figuring that there is not likely to be much in the way of "impurities" in the residue, and that this residue will help ensure that the new mix remains saturated over time.

--cn

 

[Greg Hiller]

>Greg, what do you do when it's gone, do you dump the old residue and rinse out your bucket, or just dump the new in on top of the old?<

I do not rinse the container. I add more water, then add more calcium hydoxide/oxide powder in the ballpark ratio to the amount of water I add. I stir the mess up then let it settle overnight. It's probably not a good idea to be pumping in a lot of the solids from the bottom of the bucket as they might have precipitated/concentrated nasties. About once a year I rinse out the container. I'm careful to make sure that the draw off tube does not extend (or have any risk of falling to) to the bottom of the bucket.

>figuring that there is not likely to be much in the way of "impurities" in the residue<

The problem is not likely the impurities in the calcium hydroxide/oxide, the problem is more likely to be small amounts of impurities in the precipitate. Although you might use RO/DI water, any trace amounts of metals that get though will precipitate in your kalkwasser reservior. If you follow my procedure for a long time, then one day stir the mess up and dose before it has settled you might end up dosing a lot of metals at once into your tank. Theorectical, but best to be careful, particularly if you do not very carefully monitor the water coming out of your RO/DI system.

 

[Greg Hiller]

Moe,

This thread is quickly becoming an informational thread!!

 

[conrad]

Thanks Greg, that was pretty much my understanding and what I've been doing. I use RO/DI from Skipton's and presume they monitor their output and/or have a maintenance schedule in place. And of course I always let the KW settle before dosing it.

Sorry about hijacking this thread. Maybe if others find the information useful it can be broken out and put somewhere else.

--cn

 

[Shallowwaters]

Yep, my results checked out too. I added about 45 gallons of RO/DI plus 2 1/4 cups of our new white powder to my Rubbermaid Brute trash can and got 12.8 pH before settling. My water is typically 55 degrees. Maybe I need to recalibrate my pH probe, but the results close enough for me to measure the calcium hydroxide for saturation.

But, now I have a question for Greg. If a fully saturated solution is desired and if the resultant pH will settle out impurities - do I need to use RO/DI for kalkwasser? Or can I just just use RO or just tap water??

I should have asked this BEFORE I had 200 gallons/day RO/DI capacity, but I'm still curious.