IrC
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Aluminate chemistry
While I have a passing knowledge of chemistry, I am far from the bulk of the posters here so I have a question which has been on my mind lately. I am
trying to find a cheap and easy way to make strontium aluminate. Now if I were trying to make say sodium aluminate, I would put aluminum in a sodium
hydroxide solution, with the result being my desired goal along with hydrogen gas (I assume).
Problem is I really cannot find cheap sources of strontium hydroxide, all I have besides the nitrate is the carbonate. I spent a week trying an idea I
got from an old chemistry reaction handbook, that is, strontium carbonate plus H2O yields strontium hydroxide plus carbon dioxide. But no matter what
I try the solution does not even become basic. I am wondering if anyone can tell me, if I were to make sodium or potassium aluminate, would adding
strontium to this result in the replacement of the undesired element, i.e. Na or K, with Sr? If so, could I use the carbonate? I also can add
strontium metal to water to make the hydroxide. Problem is I only have a few grams of it and it has so far been very expensive when I can find a
source. Also, it keeps wanting to turn into the carbonate from just the CO2 in the air from respiration, meaning I need to stop breathing to play
around with these ideas.
What I am trying to do is make glow powders, using my kiln, strontium aluminate, and various combinations of other elements in the actinide and
lanthanide groups, along with sulphur (in one of the formulations), as is stated in the hundreds of patents I have been looking at lately.
So far the best I can obtain is using a small amount of strontium aluminate with some uranium metal (which I oxidized), along with europium and
yttrium oxides. Problem is I really cannot afford to buy large amounts of strontium aluminate (hard to locate, expensive, and so is the hydroxide) and
do these experiments, so here I am asking, does anyone know how to take cheap and easy to get stontium carbonate and turn it into the hydroxide, as is
mentioned in: "A Dictionary of Chemical equations", A.F. Gilman, Jr. 1956, page 288; the formula given is: SrCO3 + H2O = Sr(OH)2 + CO2.
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12AX7
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Well, you can remove it with acid and neutralize with base, or try to precipitate it out. Strontium isn't too soluble, albeit more soluble than
say calcium, but it looks like SrCO3 is less soluble than CaCO3 nonetheless.
Or you can just sinter it...
Edit: calcines at yellow heat, FYI.
Tim
[Edited on 23-5-2005 by 12AX7]
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chemoleo
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Indeed, it should be quite simple.
Dissolve your SrCO3 in HCl, acetic acid, whatever that yields a soluble salt. Beware enormous bubbling during dissolution (CO2)
Then add the correct amount of NaOH.
Sr(OH2) should precipitate. Sr(OH)2 has a solubility of 0.41 g per 100 g H2O, so yields are going to be good.
Alternatively, similar to the making of calcium hydroxide from CaO, you could heat the SrCO3 to red-white heat until a small test aliquot of it
doesn't produce bubbles when dissolved in an acid (indicating it is SrO rather than SrCO3). Addition of water then forms the hydroxide.
As to making strontium aluminate itself - the better known route to making it is with aluminium hydroxide (obtained by adding ammonia to
Al-salt solutions) and the respective alkali hydroxide, earth alkali here.
However, the reaction may be quite slow, as both hydroxides are rather insoluble. Try it.
Otherwise, you can always fuse the two hydroxides in the right stoichiometric proportions.
Edit: Come to think of it, I suspect that Sr(OH2), when dry, may react with Al powder in a thermite-type reaction, similar to the one with NaOH. It is
likely going to be less energetic though, so it might not go off easily.
[Edited on 24-5-2005 by chemoleo]
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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IrC
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Thanks, I will try some of these ideas.
"As to making strontium aluminate itself - the better known route to making it is with aluminium hydroxide"
Question: google is nearly useless in this, I looked at hundreds of hits to no avail on the making of strontium aluminate, it was from old 1920's
and 30's patents that I got adding aluminum to strontium hydroxide. But in web searches I come up with a zillion glow powder hits, not one of
which describes aluminate chemistry. Likewise with as many combinations of any keywords I can think of, not much online about making strontium
aluminate. What I did was look at some of the patents I had seen mentioned on this board, and search for the patents mentioned within those patents,
and so on until I had hundreds of them. Great info, other than the fact that most of them imply they have an unlimited source of various and sundry
exotic chemicals which I can never seem to find, or at least they had them 60 years ago for some reason.
I keep thinking of that line from the movie "Back to the Future", which goes: "I am sure in 1985 you can find Plutonium in every corner
drugstore but in 1955 it's a little hard to come by". I am not sure why it is so hard to find good information on aluminates, So far as I
mentioned the hits on various search engines leaves a lot to be desired. It seems the only good ones are always to places like IOP where you have to
pay to be a member or buy a PDF, a thing I would rather avoid.
As to your mention of a better known way using aluminum hydroxide, I think you are saying add strontium metal to the aluminum hydroxide solution. If
this is not correct what other way can I go? I have a few grams of strontium metal, which as I said is really expensive, but I can get the strontium
carbonate in quantity and fairly cheap. This is why I was trying to go that route. I only ask because I find it very hard to come up with good
information on the subject. I did not want to be one of those who are too lazy to search rather than just ask others, in fact I spent weeks searching,
coming up with little, before I decided to post this topic.
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Twospoons
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I've seem the term "sol-gel " used a lot with reference to strontium aluminate synthesis, though I have no details. It may be a good
lead for you though.
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chemoleo
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Well as I said the simplest would be to make the SrO from the dried hydroxide (which in turn is made from precipitation of i.e. SrCl2 with NaOH). The
SrO is fused with Al2O3 to form SrAl2O4. Alternatively, use the respective hydroxides, Sr(OH)2 and Al(OH)3, and fuse those, water will be liberated
(which is probably easier/better).
No, at no stage you have to use strontium metal!
The Sr metal is generated as part of the reaction.
I.e.
9 Sr(OH)2 + 6 Al --> 9 Sr (METAL) + 3 Al2O3 + 9 H2O
But the H2O reacts with nascent Sr metal...
9 H2O + 9 Sr --> 9 SrO + 9 H2
And the SrO reacts onwards with the Al2O3 to form the aluminate, SrAl2O4
3 SrO + 3 Al2O3 --> 3 SrAl2O4.
So altogether this is:
9 Sr(OH)2 + 6 Al --> 3 SrAl2O4 + 6 SrO + 9 H2
You could improve the reaction by adding the correct amount of Al2O3 to react onward the nascent SrO
i.e.
9 Sr(OH)2 + 6 Al + 6 Al2O3 --> 9 SrAl2O4 + 9 H2
I am not sure though that this reaction would proceed on its own, you might have to heat this in a furnace or something (i.e. the oxidation of the Al
may not be enough for the reaction to be selfpropagating).
But with those quantities you should get almost exclusively strontium aluminate.
Or, as I said, just mix Sr(OH)2 and Al(OH)3 in the correct proportions!
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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12AX7
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Hmm alkalais yes, but which would rather reduce which, Mg + Al2O3 <---> MgO + Al? Ditto calcium, strontium etc. The equilibrium for such
reactions ought to be pretty even.
If you want to make a sintered product (so far it looks like you'll need to at least calcine it somewhere anyway), the easiest way would be to
use the carbonate powder mixed with alumina (or alumina hydrate, but that shrinks more). If you still wish to make a homogenous product with aqueous
chemistry, actually I bet it'll look more like a cement. Let's see, calcine SrO and Al2O3 (seperately I suppose), add water. It hydrates
(gaining volume, causing interference fits) and reacts (forming new interlocking crystals). After a number of hours, day or weeks, it'll be
complete and you can finally fire it.
Tim
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chemoleo
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| Quote: | | but which would rather reduce which, Mg + Al2O3 <---> MgO + Al? Ditto calcium, strontium etc. The equilibrium for such reactions ought to be
pretty even. |
Yeh yeh I already said such a reaction would be less likely. Nonetheless CaSO4 reacts very nicely with Al. It might be worth a try I suppose.
The reason why I suggested to use the respective hydroxides (particularly the Al one) is because the oxide is rather unreactive (commercial Al2O3
doesn't hydrate.... in fact it can form crystals that are sold as gems). While the hydroxide is sort of activated when it is dehydrated, so
fusing this with Sr(OH2) should be more feasible.
Never Stop to Begin, and Never Begin to Stop...
Tolerance is good. But not with the intolerant! (Wilhelm Busch)
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vulture
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Another problem is that aluminates are not stoichiometric compounds, but polymers of different molecular weight, depending on the pH, temperature,
activity coefficients of the solution, etc etc etc.
One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
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akcapr
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since noone has said this it proabaly wont work, but couldnt u decompose the strontium carbonate into strontium oxide? dissolve that in water and u
have ur hydroxide. or is the decomposititon temp. of SrCO3 much too high?
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akcapr
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also, the reson ur SrCO3 hasnt formed hydroxide with water is because its very unreactive/soluble with water. IT is very soluable with ammonium
chloride. SO u could react it with that and get ammonium carbonate and strontium chloride.
btw, the decomp. temp. of SrCO3 is 1100 degrees, celsius.
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IrC
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Thanks for the ideas, heating the carbonate and then adding it to water seems to be the best method. After it has been glowing for 15 minutes, it
rapidly forms the hydroxide (very strongly basic) when dropped in water. I next mixed aluminum dust with strontium carbonate, and then held the
mixture at a bright white heat for a quarter hour. Quite a reaction when dropped in water.
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