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Author: Subject: Boron extraction from borax
bonemachine
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Boron extraction from borax

I am looking for a way to extract boron from borax or sodium perborate. Is this possible?
Nick F
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I'd guess that it'd be possible by adding conc. aq. borax to excess conc. aq. HCl, the boric acid should ppte (I think), and then reducing the boric acid with charcoal.
This will produce the amorphous allotrope; it can also form a VERY hard crystaline form by recrystalisation from molten aluminium (which could also be used for the reduction).
Boron makes a damn good fuel once you get it lit, too.
bonemachine
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hmm

I got 30% HCL an maybe i try it. Actualy boron is a hell of a good fuell if you consider that it is used with kno3 in airbag compositions for rapid compustion.
bonemachine
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I am also interested in manufacture of b(NO3)3. I had a thought that i could use kno3 as a starting material and maybe borax? Anyone have some experience?
vulture
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Reducing with Al does not work, as you get AlB12 (yes twelve), commonly referred to as "square" (quadratic) boron.
Magnesium does work.

One shouldn't accept or resort to the mutilation of science to appease the mentally impaired.
PrimoPyro
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Whoa

AlB12 wouldn't that be um 'good' for thermite fuel?

Is it especially dense?
Nick F
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AlB12? Wow.
Maybe that's actually what you get when you recrystalise B from molten Al, but I read that it was an allotrope of B.
Yes, it should make a very good fuel...
bonemachine
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Yes that fuel looks very inderesting due to it's high density. What abougt boron nitrate? Can anyone imagine if there is a possible way to synthesise it?
BromicAcid
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Here are some relevent reactions for involving boron and its oxide.

[Boric oxide or better anhydrous borax, may be reduced by an equivilent amount of metallic calcium or CaH2 The reaction is perfomed in a crucible, 5 - 10% excess CaO being added to moderate the violence of the reaction. Ignition is accomplished by igniting a fuse mixture of sodium peroxide and metalic calcium with magnesium ribbon.]

(a) B2O3 + 3Ca ---> 3CaO + 2B
(b) Na2B4O7 + 6Ca ---> Na2O + 6CaO + 4B
(c) 2B2O3 + 3CaH2 ---> 4B + 3CaO + 3H2O

[When boron trioxide is heated with twice its weight or more of finely powdered magnesium in a tightly covered iron crucible magnesium boride is formed (a), which hydrolyzes in water at 0 C, and liberates H2 (b).]

(a) B2O3 + 6Mg ---> Mg3B2 + 3MgO
(b) Mg3B2 + 6H2O ---> Mg3B2*(OH)6 + 3H2

[Boron trioxide is reduced by magnesium.]

B2O3 + 3Mg ---> 2B + 3MgO

[Hydrochloric acid (or nitric acid) reacts upon magnesium boride to form boron hexahydride. The hydride is an inflammable gas.]

Mg3B2 + 6HCl ---> 3MgCl2 + B2H6

Hope this helps, I know it did for me to fine tune a bit.
BromicAcid
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I'm re-doing some work with producing boron and I'm going the easier method of aluminum reduction. I figure that I can react the boron produced with chlorine and produce the boron trichloride which would volitize leaving the mass of Al12B and Al2O3 and be collectable. The problem is that I cannot find any resources on hand that tell me how to reduce the boron trichloride to boron except for the reaction with a hot tungsten filiment at elevated temperatues in the presence of hydrogen. So what I'm looking for is a simpiler reaction with boron trichloride to produce elemental boron. Any further help would be appreciated!

Edited to answer my own question for future generations:

2BCl3 + 3Zn ----> 3ZnCl2 + 2B (900 C)

[Edited on 1/11/2004 by BromicAcid]
chemoleo
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on an other note, I doubt that B(NO3)3 is produced easily, as this would be the nitric acid anhydride of boric acid (B(OH)3). In other words, this is NOT a salt of a hydroxide, like with Ca(OH)2 etc!

[Edited on 19-9-2003 by chemoleo]
BromicAcid
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 Quote: I am also interested in manufacture of b(NO3)3. I had a thought that i could use kno3 as a starting material and maybe borax? Anyone have some experience?

I was reading through a book "Preparative Inorganic Reactions Vol 1",specifically an article by C.C. Addison and N. Logan when I came across mention of B(NO3)3 and immediately thought of this thread:
 Quote: Chlorine nitrate is a yellow liquid, melting point -107C., boiling point (by extrapolation) +18C. The chlorine atom may be considered to carry a partial positive charge Cl+ - ONO2-, so that in its reactions the compound is a ready source of nitrate ions. A further possible advantage of chlorine nitrate lies in the fact that its reactions are not complicated by the NO+ or NO2+ ions which are inevitably present in N2O4 or N2O5. Because of its low melting point, reactions with chlorine nitrate, e.g., TiCl4 + 4ClNO3 ---> 4Cl2 + Ti(NO3)4 can be carried out conveniently at the temperature of solid carbon dioxide (-80C.) and chlorine, with excess chlorine nitrate, can be removed in vacuum at this temperature. The nitrates B(NO3)3 (-78C.), Al(NO3)3 (-7C.), and Sn(NO3)4 (-60C.) are said to be prepared in this way at the temperatures given.

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JohnWW
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B(NO3)3 would be a covalent nitrate; this class of compounds are highly explosive, like cellulose nitrate. Besides, because it is also electron-deficient, it would be polymeric, with O bridges between B atoms.
Magius
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Reduction with Al powder

Does anyone know what temperature the reduction of boric acid by aluminum would start at, and if the reaction would be exothermic?

The reaction between Calcium and sodium tetraborate that Bromic mentioned seems interesting. Could the use of HCl be skipped the tetraborate be reduced directly, looking something like this?

3Na2B4O7 + 13Al ---> 3Na2O + 6Al2O3 + AlB12

Would there be anyway to seperate the Al2O3 from the AlB12? This fuel looks very interesting for a themite reaction.
cyclonite4
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To seperate Al2O3 and AlB12, try mixing with a stoichiometric amount of NaOH, to form the tetrahydroxyaluminate ion, which is soluble in water. I'd give you the stoich now, but i'm about to goto sleep and cant be bothered figuring it, shouldn't be to hard for you.

[Edited on 25-12-2004 by cyclonite4]

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S.C. Wack
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The Al and Mg reactions all seem to use a large amount of S as well, so I thought that it ought to be mentioned.
cyclonite4
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@S.C. Wack: By 'S' do you mean sulfur, because I can't see one mention of the word sulfur . What do you mean by 'S'?

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BromicAcid
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For what purpose do you want the AlB12, it's fairly inert to everything.
 Quote: Does anyone know what temperature the reduction of boric acid by aluminum would start at, and if the reaction would be exothermic?

I believe that even the reaction of boric acid with aluminum once initiated would be exothermic. When I did a thermite type reaciton between boric oxide and aluminum the oxide was made by dehydration of boric acid and probably still contained an appreciable precentage of it, the mix itself upon heating would not ignite, but when a very small area of it was mixed with KClO4 that part quickly caught fire and the heat spread through the rest of the reaction mass.

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S.C. Wack
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So you can't see one mention of the word sulfur - this means that you haven't looked at the preparations of B (from Mg) or AlB12 in Brauer's Handbook of Preparative Inorganic Chemistry, Schlessinger's Inorganic Laboratory Preparations, or Biltz's Laboratory Methods of Inorganic Chemistry. Well, I have, thus my earlier post. It seems to be preferred.
JohnWW
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Are those on the forum's FTP?
S.C. Wack
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Alchemist uploaded the English version of Brauer to the FTP. It was available as a torrent at roguesci. I might make a better one, because quality (and in places legibility) was sacrificed for speed. Mephisto did an excellent job with the original German set and it is in his folder. I did Schlessinger (which only mentions the Al exp) myself, it isn't pretty and my last few uploads were done much better.

I didn't think that the whole Biltz, Hall, and Blanchard book was worth doing entirely and I'm not uploading a partial book. The details there for these experiments (both use S and give no alternative) are in part contained in the related prep of Si (though not as abbreviated as with Schlessinger), so I'll give Brauer's:

Boron
I. According to Moissan, very impure amorphous boron, containing
about 80-90% B, is obtained by the reaction of B2O3 with magnesium.
According to Kroll the optimum yields are obtained as follows: A
fireclay crucible, appoximately 20 cm. high and 16 cm. in diam-
eter, is painted with a paste of ignited MgO and sintered MgCl2 and
dried in a low-temperature oven. A mixture of 110 g. of B2O3,
115 g. of Mg shavings (the use of Mg powder frequently leads to
explosive reactions) and 94 g. of powdered S is placed in the cruc-
ible. The reaction is started with an ignition pellet, after which it
proceeds vigorously. After the mixture is cooled, it is extracted
in water and then in dilute HCl for a week. The residue is treated
several times by heating with HF and HCl, washed with water and
dried in vacuum at 100C. The yields are variable, with a maximum
of 46%

AlB12
A mixture of 50 g. B2O3, 75 g. of S and 100 g. of Al (all the
reagents must be dry) is reacted in a fireclay crucible. After
cooling, the melt is removed from the crucible and pulverized, and
water is added. After elutriation of the slag, the reduced particles
are sorted out from the residue, separated as far as possible from
the slag, and treated with concentrated HCl until a brilliant black
crystalline residue remains. The latter is treated with 40% HF in a
Pt crucible, washed with water and left in HCl until gas evolution
ceases. It is then filtered, washed and dried.
I am a fish
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Preparation of Boron Trioxide

I am planning to make boron trioxide from boric acid.

When heated at 100&#xb0;C, boric acid decomposes into metaboric acid:
H<sub>3</sub>BO<sub>3</sub> &rarr; HBO<sub>2</sub> + H<sub>2</sub>O

When heated further, metaboric acid decomposes into boron trioxide:
2HBO<sub>2</sub> &rarr; B<sub>2</sub>O<sub>3</sub> + H<sub>2</sub>O

However, I don't know the conditions for the second reaction. Does anyone know what temperature and duration of heating is required to reliably complete the conversion?

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chemoleo
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Didn't Bromic do a reaction with it somewhere? I think he also tried a thermite.

Anyway, I also made it a while ago, from boric acid - I just heated it until no more bubbling would occur (under a bunsen). This then produced a glassy mass that could be pulled into superthin threads. As far as I remember it is also slightly irritant to the nose (that is, the dust).

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I am a fish
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I made some boron trioxide today. I obtained a glass-like substance. However, it certainly couldn't be pulled into threads. When I tried, it merely shattered. I wonder what was different between the procedures we used.

Chemoleo: What temperature was your boron trioxide at when you pulled it into threads? I previously assumed that you had let it cool to room temperature.

[Edited on 25-3-2005 by I am a fish]

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12AX7
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Well, when molten. Like glass. Matter of fact, borax is essentially a lower-melting, somewhat softer analog of silica, which also forms glass, pure.

Tim
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