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bluamine
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Do calcium hydroxide react with aluminum sulfate?
Hi everyone!!
Can this reaction really happen:
3Ca(OH)2+Al2(SO4)3=2Al(OH)3+3CaSO4??!!
I found it on s YouTube video & I know that it is not a trustful science source, especially when it comes to a video existing only on an unknown
channel
[Edited on 29-11-2015 by bluamine]
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gdflp
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Under what conditions? If they are both dissolved in water then yes, it is just a simple metathesis reaction.
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aga
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Had to look that up, it being the second time i saw it in relation to something that appeared simple.
Wiki:
"A salt metathesis reaction (from the Greek μετάθεσις, "transposition"), sometimes called a double replacement reaction"
Much better (for me at least) !
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bluamine
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Quote: Originally posted by gdflp  | | Under what conditions? If they are both dissolved in water then yes, it is just a simple metathesis reaction. |
i am comfused about it because calcium hydroxyde is not soluble at least in water
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gdflp
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It is to some extent, about 2g/L at 20°C. Much more soluble than alumina.
[Edited on 11-29-2015 by gdflp]
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aga
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At STP it's not.
As gdflp asked, "under what conditions" ?
Makes a whole lot of difference.
Edit:
Now you mention it (and i look up the other three) none of them are particularly soluble in water apart from the Al Sulph.
[Edited on 29-11-2015 by aga]
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bluamine
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| Quote: Originally posted by aga | At STP it's not.
As gdflp asked, "under what conditions" ?
Makes a whole lot of difference.
Edit:
Now you mention it (and i look up the other three) none of them are particularly soluble in water apart from the Al Sulph.
[Edited on 29-11-2015 by aga] |
Well i can't increase thé pression so much at home, but if it must be done at a moderately high tempreature, I can do it..
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aga
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It would probably be better blueamine to say what you Want to do, and what reagents you have available.
Please put stuff like this in the Begnings Topic in future.
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bluamine
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| Quote: Originally posted by aga | It would probably be better blueamine to say what you Want to do, and what reagents you have available.
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I just want to produce some amounts of alumina. I do know many other methods to do that, but if this method work, it would be the easiest one. Unless
the sand thermite methods can make me able to formalize alumina
Sure
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aga
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Hmm.
I didn't know what 'alumina' meant and had to go to wiki again : aluminium(III) oxide looks hard to do.
If you want Aluminium Hydroxide Al(OH)3 just try making Aluminium Sulphate, screw it up, and it's present in bucketloads.
http://www.sciencemadness.org/talk/viewthread.php?tid=30313
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bluamine
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| Quote: Originally posted by aga | | I didn't know what 'alumina' meant and had to go to wiki again : aluminium(III) oxide looks hard to do. |
Unfortunately, this is what I am looking for
[Edited on 29-11-2015 by bluamine]
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aga
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Buy some ?
Might be easier/cheaper.
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gdflp
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Do you have any basic sodium or potassium salts? Hydroxide, carbonate, and bicarbonate solutions will all precipitate aluminum hydroxide from a
solution of an aluminum salt, careful of the release of CO<sub>2</sub> if the latter two are used though. A stoichiometric amount should
be used as well due to the amphotericity of aluminum hydroxide. From here, calcining the aluminum hydroxide will yield aluminum oxide, in small
amounts this should be quite doable in a porcelain crucible with a propane torch or bunsen burner. Aluminum oxide is also quite cheap from many
pottery suppliers, only several dollars per pound if you want to go that route.
[Edited on 11-30-2015 by gdflp]
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bluamine
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Where can I find it?!
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aga
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Ebay !
http://www.ebay.co.uk/itm/white-fused-alumina-Optical-Glass-...
Cheaper:
http://www.ebay.co.uk/itm/Microdermabrasion-crystals-alumini...
[Edited on 29-11-2015 by aga]
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deltaH
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It also depends on how pure you want your product. If you're using lime, I'd be really worried about also forming calcium aluminate.
If you want a very pure material, then I would precipitate a saturated aluminium nitrate solution containing crushed ice with an ice cold 30% ammonia
solution, the cold being employed purely to minimise the escape of noxious ammonia fumes. This would form aluminium hydroxide and ammonium nitrate.
I'd then boil the slurry to break the aluminium hydroxide slimes and make powder before filtering (this doesn't always work). Then you will have
aluminium hydroxide contaminated with a small amount of ammonium nitrate, however, a mild calcination carried out as a slow heating ramp up to 200°C
outside will decompose the ammonium nitrate completely to gases only (nitrous oxide and water vapour), so ultimately you will be left with an
extremely pure Al(OH)3 powder.
The result is a material known as gibbsite, Al(OH)3. When you bake gibbsite at higher temperature, it will lose water and convert into boehmite,
AlOOH. This is also often called γ-alumina. It has a relatively high specific surface area and is used in the manufacture of catalysts.
If you heat boehmite in a furnace to very high temperature (>1000°C), you dehydrate the boehmite further and form α-alumina, Al2O3. It will no
longer be microporous and will have lost its high specific surface area. In this state, it's used as an abrasive and to prepare refractories.
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bluamine
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Thanks for the links but.. I can't buy anything online.. At least at the moment.
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bluamine
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| Quote: Originally posted by deltaH | It also depends on how pure you want your product. If you're using lime, I'd be really worried about also forming calcium aluminate.
If you want a very pure material, then I would precipitate a saturated aluminium nitrate solution containing crushed ice with an ice cold 30% ammonia
solution, the cold being employed purely to minimise the escape of noxious ammonia fumes. This would form aluminium hydroxide and ammonium nitrate.
I'd then boil the slurry to break the aluminium hydroxide slimes and make powder before filtering (this doesn't always work). Then you will have
aluminium hydroxide contaminated with a small amount of ammonium nitrate, however, a mild calcination carried out as a slow heating ramp up to 200°C
outside will decompose the ammonium nitrate completely to gases only (nitrous oxide and water vapour), so ultimately you will be left with an
extremely pure Al(OH)3 powder.
The result is a material known as gibbsite, Al(OH)3. When you bake gibbsite at higher temperature, it will lose water and convert into boehmite,
AlOOH. This is also often called γ-alumina. It has a relatively high specific surface area and is used in the manufacture of catalysts.
If you heat boehmite in a furnace to very high temperature (>1000°C), you dehydrate the boehmite further and form α-alumina, Al2O3. It will no
longer be microporous and will have lost its high specific surface area. In this state, it's used as an abrasive and to prepare refractories.
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Thank you for all these important informations. I am looking for both α & γ alumina, & I have no choice, I have to use sodium hydroxide,
because bicarbonate is more expensive.
Unfortunately, sand thermite method is the simplest, but it can't help to make something using alumina
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deltaH
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Sodium hydroxide will work fine as well, ammonia is only used when you want it ultrapure. I wouldn't use calcium hydroxide for the reason stated
earlier.
Don't forget that boiling sometimes helps to break slimes in precipitations like this. It can make filtering easier if you can convert it to a powdery
material first. If you get a powder that filters nicely, then you can easily wash out the sodium chloride.
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MrHomeScientist
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| Quote: Originally posted by bluamine | Hi everyone!!
Can this reaction really happen:
3Ca(OH)2+Al2(SO4)3=2Al(OH)3+3CaSO4??!!
I found it on s YouTube video & I know that it is not a trustful science source, especially when it comes to a video existing only on an unknown
channel
[Edited on 29-11-2015 by bluamine] |
To address the original question, this reaction proceeds because of the high insolubility of calcium sulfate. While 3 of 4 of those compounds are
pretty insoluble, the very high insolubility of CaSO<sub>4</sub> drives the reaction forward. Because it involves lots of insolubles, I
expect the reaction to be very slow and difficult to determine the endpoint.
Aluminum sulfate is reasonably soluble, though, so here's how I would do it: Dissolve Al<sub>2</sub>SO<sub>4</sub> in water,
then add enough solid Ca(OH)<sub>2</sub> to make a slurry. Vigorously stir and heat for several hours, then filter the solids off. Make
use of aluminum's amphoteric nature by adding enough NaOH to dissolve the produced aluminum hydroxide. Filter off the still-insoluble calcium sulfate,
then take the solution and re-precipitate the aluminum as hydroxide by lowering the pH with some acid. Convert to alumina by calcining.
Edit: Of course now that I typed all that, I realized you could skip a lot of the intermediate steps by just making a solution of
Al<sub>2</sub>SO<sub>4</sub> slightly basic. This precipitates the hydroxide and you can filter and calcine from there. Not
too basic, or the aluminum will re-dissolve!
[Edited on 11-30-2015 by MrHomeScientist]
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gdflp
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Calcium sulfate is more soluble in water than calcium hydroxide, (2.05g/L vs. 1.60g/L) and much more so than aluminum hydroxide. The reaction is
driven by the low solubility of aluminum hydroxide, which is only about 1mg/L at STP; not that of CaSO<sub>4</sub>.
Technically this reaction could be cleanly done by fully dissolving the calcium hydroxide in water, mixing with a stoichiometric amount of aluminum
sulfate solution, and allowing the precipitate to settle, but the volumes of water involved would be come so large as to be impractical. As long as
the precipitate is dense enough, it might be worth a try in a 5 gallon bucket, though mechanical losses involved in filtering the precipitated
aluminum hydroxide may kill the yield.
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AJKOER
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OK, Bluamine, so you wish to acquire a large quantity of Al2O3 (although you did not honestly reveal this at first citing a reaction creating Al(OH)3
), possibly for a thermite. I assume large because in such amounts even NaHCO3 to quote yourself "because bicarbonate is more expensive" and not
interested in working with cheap aqueous ammonia, which on a large scale would be problematic.
You have no credit (but claim to be around 23 years of age) or do not wish to leave any paper trail as to your identity/location, as you cannot buy
online.
You known little chemistry, are a relatively recent members with 40 posts, and, I would guess, you are not a student, and your goal is to use
chemistry for singular not specified reasons.
Excuse me, but I, for one, am suspicious of your intent, and would ask other members to be wary.
[Edited on 1-12-2015 by AJKOER]
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MrHomeScientist
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What possible clandestine use does alumina have?
Also thanks gdflp, I thought calcium sulfate was the nigh-insoluble one.
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AJKOER
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Someone with a background in chemistry could use alumina as a catalyst, as is, or mixed with other materials to act as one.
One may also think (mistakenly) it is employed directly in flash powder or thermites, or can be transformed to aluminum powder.
If I am correct in assuming it is needed/desired, even mistakenly, in large quantities, sorry but it makes me suspicious.
Not doubt, I could be in error and apologize again (perhaps getting paranoid).
[Edited on 1-12-2015 by AJKOER]
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bluamine
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| Quote: Originally posted by AJKOER | OK, Bluamine, so you wish to acquire a large quantity of Al2O3 (although you did not honestly reveal this at first citing a reaction creating Al(OH)3
), possibly for a thermite. I assume large because in such amounts even NaHCO3 to quote yourself "because bicarbonate is more expensive" and not
interested in working with cheap aqueous ammonia, which on a large scale would be problematic.
You have no credit (but claim to be around 23 years of age) or do not wish to leave any paper trail as to your identity/location, as you cannot buy
online.
You known little chemistry, are a relatively recent members with 40 posts, and, I would guess, you are not a student, and your goal is to use
chemistry for singular not specified reasons.
Excuse me, but I, for one, am suspicious of your intent, and would ask other members to be wary.
[Edited on 1-12-2015 by AJKOER] |
1.I supposed that the title is clear, so I don't have to mention that. Sorry for the inconvenient.
2.I know my questions seem pretty weird, & I was accused of trolling in another forum, but I have serious problems which makes many chemicals
unavailable for me. Unfortunately, ammonia is one of them.. I am not sure if i can buy calcium cyanamide, if so I would use it to produce ammonia,
because I need it to produce magnetite (I would discuss that in another topic).
3.I prefer using hydroxide because I wish to make it at home (1kg of sodium chloride costs here about .3 $ very cheap). On the other side, I can buy
15g of bicarbonate for about 0.05 $.
4.If I was looking for thermite, I would use hematite & aluminum or any other method (I mentioned sand thermite which I know how to make it)
without using aluminum oxide.
5. I did not lie when I wrote that I am a 23 yo student, & I am using chemistry for both personal reasons & others reasons related of my study
(though unfortunately my major is not chemistry).
6.Some members post here many much more dangerous topics (like RDX's one for example), & I did not read anything like this reply there.
7.I am just a guest here, if moderators believe that I must not post anything here, they have completely the right to ban me
[Edited on 1-12-2015 by bluamine]
[Edited on 1-12-2015 by bluamine]
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