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JJay
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OTC Calcium Hydroxide
Where is a good place to obtain small quantities of calcium hydroxide OTC? I've heard and read that it is sometimes available in food grade as
"pickling lime" for preparing crisp pickles, but I checked several health food, craft, brewing, department, grocery, and home improvement stores and
didn't find any pickling lime. Technical grade Ca(OH)2 It is available very inexpensively from home improvement and gardening stores as "hydrated
lime," but they generally sell it in large quantities, and I don't want to store more than a couple of kilograms.
Any ideas?
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Bert
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Um, make it yourself?
http://www.lowtechmagazine.com/2013/09/lime-kilns.html
Rapopart’s Rules for critical commentary:
1. Attempt to re-express your target’s position so clearly, vividly and fairly that your target says: “Thanks, I wish I’d thought of putting it
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byko3y
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In fact they sell something which is not a hydrated lime, but a mixture of CaCO3+Ca(OH)2. So I've got no source of OTC Ca(OH)2 too, I'm forced to make
it from CaCl2 and NaOH.
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JJay
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Ca(OH)2 is much more soluble in water than CaCO3, right?
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violet sin
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Gardening shop. 10# bag of hydrated(slacked) lime for $ 1.95 isn't bad.
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RareEarth
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Calcium Salts usually have very poor solubility in water, in my experience. According to wikipedia this seems to be the case for both Calcium
Hydroxide and Carbonate
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JJay
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Calcium hydroxide is 100x as soluble in water as calcium carbonate... but the hydroxide's solubility is low too... less than 2 grams will dissolve in
a liter of water....
Mixing NaOH and CaCl2 looks like it will work well for creating pretty darn pure Ca(OH)2.
[Edited on 27-10-2015 by JJay]
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Magpie
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Safeway grocery stores and Ace hardware sell pickling lime in my city. I can also buy hydrated lime by the pound at my local garden stores - bring
your own container.
[Edited on 27-10-2015 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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RareEarth
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Quote: Originally posted by JJay  | Calcium hydroxide is 100x as soluble in water as calcium carbonate... but the hydroxide's solubility is low too... less than 2 grams will dissolve in
a liter of water....
Mixing NaOH and CaCl2 looks like it will work well for creating pretty darn pure Ca(OH)2.
[Edited on 27-10-2015 by JJay] |
Given the solubilities, I would agree. But, where do you plan to get CaCl2, that you can't also get Ca(OH)2?
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careysub
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Latin markets sell calcium hydroxide as "cal" or "cal mexicana". It is used to treat corn (nixtamalization) to make masa (corn dough).
Not all regions have equal access to Latin markets of course.
[Edited on 27-10-2015 by careysub]
[Edited on 27-10-2015 by careysub]
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j_sum1
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| Quote: Originally posted by RareEarth | | Quote: Originally posted by JJay | Calcium hydroxide is 100x as soluble in water as calcium carbonate... but the hydroxide's solubility is low too... less than 2 grams will dissolve in
a liter of water....
Mixing NaOH and CaCl2 looks like it will work well for creating pretty darn pure Ca(OH)2.
[Edited on 27-10-2015 by JJay] |
Given the solubilities, I would agree. But, where do you plan to get CaCl2, that you can't also get Ca(OH)2? |
My supermarket, which is within walking distance of my home, sells NaOH and CaCl2. I don't think they sell Ca(OH)2.
But, point taken. Ca(OH)2 should not be too difficult to find.
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violet sin
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Damp-rid is CaCl2 prills for moisture control sold at rite-ade in the camping department for under 2$.
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JJay
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Something like this....
Preparation of Calcium Hydroxide (experimental)
Every time reagents are mixed in this procedure, the resulting solution will get hot, so add reagents slowly.
Place 100 mL distilled H2O in a 250 mL beaker. Carefully add 40.00 g NaOH with stirring until it dissolves. In a 500 mL beaker, place 100 mL H2O and
add 55.49 g anhydrous CaCl2 with stirring until all CaCl2 dissolves. Add NaOH solution to CaCl2 solution with vigorous stirring. Ca(OH)2 crystals will
precipitate. Rinse 250 mL beaker with 10 mL H2O to ensure that all NaOH is added to the reaction mixture; when both solutions are completely mixed, pH
of the result should be slightly basic. Filter the reaction mixture while still hot and wash with hot H2O. Dry the crystals and calculate the yield.
[Edited on 27-10-2015 by JJay]
[Edited on 27-10-2015 by JJay]
[Edited on 27-10-2015 by JJay]
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JJay
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If someone wants to check my stoichiometry and make sure I didn't accidentally try to dissolve 10x too much of a compound in distilled water before I
actually try out this procedure, be my guest.
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RareEarth
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I don't see anything wrong. To ensure maximum conversion of the NaOH, it wouldn't hurt to use excess CaCl2. Any leftover will just stay dissolved in
the water with the NaCl anyways. Wouldn't make too much of a difference, but wouldn't hurt either.
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gdflp
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I don't think that will work. The stoichiometry looks right, but calcium hydroxide doesn't cleanly precipitate out of such concentrated solutions.
Instead of an easily filterable precipitate, you will get something with around the consistency of toothpaste. I would dilute the solutions at least
5x to get a successful reaction mixture which will filter easily.
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violet sin
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Don't think the CaCl2 is anhydrous in damprid. So unless you have a source specifically stating it's purity and hydration, weights may be
a touch off. I seem to remember reading it was often sold as a lower hydrate that still allowed it to absorb moisture. I'll look around later on the
laptop, phone use to scrounge up data sux.
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DistractionGrating
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Google "kalkwasser for sale".
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JJay
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| Quote: Originally posted by gdflp | | I don't think that will work. The stoichiometry looks right, but calcium hydroxide doesn't cleanly precipitate out of such concentrated solutions.
Instead of an easily filterable precipitate, you will get something with around the consistency of toothpaste. I would dilute the solutions at least
5x to get a successful reaction mixture which will filter easily. |
This seems like very sound and reasonable advice. Mixing more dilute solutions will be safer too.
[Edited on 27-10-2015 by JJay]
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NedsHead
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The last time I needed a small amount of calcium hydroxide I drove to the nearest housing development area and politely asked a brick layer, he put a
shovel full into a bag for me and refused to take a cent for it.
Any housing development happening near you?
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JJay
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| Quote: Originally posted by RareEarth | | I don't see anything wrong. To ensure maximum conversion of the NaOH, it wouldn't hurt to use excess CaCl2. Any leftover will just stay dissolved in
the water with the NaCl anyways. Wouldn't make too much of a difference, but wouldn't hurt either. |
I agree.
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JJay
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I'm going to carry out the following procedure:
Preparation of Calcium Hydroxide (experimental)
Place 100 mL H2O in a 250 mL beaker. Carefully add 8.00 g NaOH with stirring until it dissolves. In a 500 mL beaker, place 100 mL H2O and add 30 g dry
tech grade CaCl2 (as ice melt) with stirring until all CaCl2 dissolves. Add NaOH solution to CaCl2 solution with vigorous stirring. Ca(OH)2 will
precipitate. Rinse 250 mL beaker with 10 mL H2O to ensure that all NaOH is added to the reaction mixture; when both solutions are completely mixed, pH
of the result should be slightly basic. Measure and record the pH and temperature. Filter the reaction mixture while still hot and wash with hot H2O.
Dry the crystals in a sealed container over CaCl2 and calculate the yield.
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JJay
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If I wanted an analytically pure product, I think I would purify the NaOH by crystalizing it from methanol (probably not necessary) and purify the
Ca(OH)2 by crystalizing it from glycerine.
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Deathunter88
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Nile Red's video might be helpful.
http://www.youtube.com/watch?v=G26uzosONGk
(Nile Red's video, not mine)
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JJay
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I performed the experiment. It was successful; I am waiting for the product to dry so I can calculate the yield.
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