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Strepta
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ec1: I have tried the microwave experiment with activated charcoal and H3PO4 (85%). The idea was to adsorb the H3PO4 onto the charcoal for intimate
contact. The charcoal is the microwave absorber as well. Quite a bit of fixturing effort went into the experiment. I attempted to control the
microwave power by using a variac to reduce the drive the hv transformer. It then became necessary to provide a separate filament supply which was not
affected by the variaac to avoid early tube cutoff. There was plumbing (glass tubing) through holes drilled in the sidewalls of the microwave to
provie an inert gas blanket for the reaction. I even built a microwave detector using a UHF diode, LED, cap and resistor to check for “leaks”
around the drilled holes. All in all, quite a lot of effort went into it, but the experiment was not successful. This was a few years back, and all my
equipment and notes are currently in storage, so I’m trying to remember just what happened.
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aliced25
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Maybe activated charcoal and polyphosphoric acid? It should be easy enough to remove the door and change it to a bolt-on model with a bloody great
gasket sealing the system, then a flask (or better cheap quartz like Len1 used in his furnace), to a length of tubing sealed to it (wrapped with
something in case MW's come through) with sodium silicate/glass wool passing through the wall into a trap. If you used another tube to run in an argon
line to the sealed system, then we would have a sealed, inert gas system pretty simply.
I'm actually considering it for both POCl3 and SiCl4 (I'm guessing here, but I suspect Si heats up awful quick in MW radiation - pass dry Cl2 into it
and I wonder what happens?). Could be useful for those without a furnace.
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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Strepta
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For the future I would go easy on the fixturing until I had demonstrated proof of concept. Proceed incrementally, using very small amounts of
materials (~.1g) and see if you can detect any product. Its always easy to scale up once you have established procedural parameters. Also, if/when
modifying a microwave, remember that distance is your best friend. Its easy to retire a few feet and allow an experiment to complete before checking
the result.
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aliced25
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What about silicon? Mixed intimately with polyphosphoric acid, it would have to be an oxygen scavenger, it would also remove the last traces of
ammonia (by forming the nitride). Maybe a carbon-based compound that is looking for oxygen, oxalic acid, citric acid, something that will remove
oxygen to form CO2, instead of trying to use pure carbon? Is there maybe a chemical solution to removing the oxygen by combining it with an organic in
a solid-solid, liquid-gas reaction?
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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aliced25
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Ok, I'll try one more time - there is a host of data on the silico- and alumino-thermic reduction of MgO with Calcium Oxide, for example the following
papers:
Barua, S.K. & Wynnyckyj, J.R., 1981 "Kinetics of the Silicothermic Reduction of Calcined Dolomite in Flowing Hydrogen' Can. Metallurgical
Quarterly, vol.20(3), pp.295-306 (DOI: http://dx.doi.org/10.1179/000844381795270165)
Grjotheim, K., Herstad, O. & Toguri, J.M., 1961 'The Aluminum Reduction of Magnesium Oxide: I. The Vapor Pressure of Magnesium over the System
Al-MgO' Can. J. Chem. vol.39(3), pp.443-450 (DOI: 10.1139/v61-053)
Grjotheim, K., Herstad, O. & Toguri, J.M., 1961 'The Aluminium Reduction of Magnesium Oxide: II. The Vapor Pressure of Magnesium over the System
Al-MgO-CaO' Can. J. Chem., vol.39(11), pp.2290-2294 (DOI: 10.1139/v61-303).
Grjotheim, K., Herstad, O., Skarbö, R. & Toguri, J.M., 1963 'The Aluminium Reduction of Magnesium Oxide: III. The Vapor Pressure of Magnesium
over the System Al-Mg2SIO4 (Olivine)' Can. J. Chem., vol.41(3), pp.739-742 (DOI: 10.1139/v63-105).
Toguri, J.M & Pidgeon, L.M, 1961 'High-Temperature Studies of Metallurgical Processes: Part I. The Thermal Reduction of Magnesium Oxide with
Silicon' Can. J. Chem., vol.39(3), pp.540-547 (DOI: 10.1139/v61-065).
Toguri, J.M. & Pidgeon, L.M, 1962 'High-Temperature Studies of Metallurgical Processes: Part II. The Thermal Reduction of Calcined Dolomite with
Silicon' Can. J. Chem., vol.40(9), pp.1769-1776 (DOI: 10.1139/v62-271)
You'll note I haven't linked them (or uploaded - it won't let me they're too big) but the Canadian ones have free full-text online.
Now, notice they briquette the reagents together, under pressure, THEN heat them, while they are in intimate contact? Yes, the reactions are run in a
vacuum (about what a basic roughing pump would pull), so I'd be interested if someone wanted to play around with the thermodynamics - the Mg produced
by the Pidgeon process is unfavorable, but it is driven to the right by the removal of the gaseous Mg, as we would do with gaseous P, so there is a
correlation. With a pipe and a burner design using LPG (Propane/Butane & air) it should be possible to get into the right area heat wise.
Would be an interesting model - aluminium and silicon can be used to reduce a shitload of things.
[Edited on 2-5-2013 by aliced25]
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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elementcollector1
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Is it possible to mix silicon carbide into the charge, for better microwave-heating? It would appear to be relatively inert, and is easy to
find in a very fine, powdered form (used for rock tumblers as the penultimate polishing stage). It's also very receptive to microwaves, possibly more
so than activated charcoal.
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watson.fawkes
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Quote: Originally posted by elementcollector1  | | Is it possible to mix silicon carbide into the charge, for better microwave-heating? It would appear to be relatively inert, and is easy to
find in a very fine, powdered form (used for rock tumblers as the penultimate polishing stage). |
It would
certainly get hot, but it's a mistake to think that it wouldn't react. SiC is used for open-air heating elements, and its lifetime is determined by
how well its oxide passivation layer is maintained; it's made of SiO2. Thermal cycling causes cracks to propagate inward.
If it were part of the charge, it would be hottest part of the charge, always. It's going to vaporize something in its vicinity, and expect part of
that gas to include some oxygen, some very hot and reactive oxygen. The carbon reacts away as a gas; the silicon makes a medium-melting glass.
Certainly at the particle surface it will be hot enough to keep the glass molten. That indeed might be a good thing, perhaps. Now it might work if you
don't need very much SiC, and the effects of silica on the melting point of the glass are tolerable. Certainly if you are expecting to operate at
higher glass temperatures, it's likely not a problem at all.
I'd also investigate the impurities from technical grade SiC. I'd want to know how much arsenic was present, for example. I'd hate to be surprised
about that one.
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aliced25
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I'd be more inclined to mix finely powdered silicon with the charge, it is a decent susceptor and it is a powerful reducing agent.
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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12AX7
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Remember that molten glass is conductive (at least the kinds with ions in them, sodium, calcium, etc.), and will take over once the SiC has begun
fusing the mixture.
Is P4 vapor sensitive to microwaves, does it absorb? I shouldn't think so, but perhaps superheated vapor contains enough radicals or ions to do
something? Thought being, as the vapors leave the reactor, they might not do so without side effects.
Tim
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plante1999
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I just tried to react molten sodium hexametaphosphate and calcium carbide together, about 3 g, at first, a small burst of acetylene was made, then at
bright yellow heat, some flammable phosphorus gas evolved from the melt, nothing of real interest taught.
I never asked for this.
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aliced25
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Try with silicon - I have (Hopefully) my last exams on at present (from then on theses ) and have neither the time or the money (unfortunately). I have seen calcium silicide on some pyro sites for bugger all, it should reduce
everything rapidly.
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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elementcollector1
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I've been looking at Magpie's setup back on page 41 and I don't quite understand - why is the retort so insulated with cement? Can metal not do the
job (is it corroded / melted / etc.)? I'd like to try this myself on a smaller scale with a soup can, but I'm not sure that I should coat the insides
with cement (would regular cement instead of furnace cement make any difference?)
Also, I'd like my sample of phosphorus to be red, so if I leave the white phosphorus (after cleaning) underwater in the sunlight, should it decompose
fully?
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plante1999
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At the moment, I'm trying to turn 1.5g of white phosphorus to red, and I must say it take a LOT of time in Canada, I keep it inside, so it can become
hotter, but it is not something done in a week, at some point I will need to scrape the phosphorus on the side, and re-cap the vial.
I never asked for this.
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elementcollector1
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I thought sun was more important than heat?
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plante1999
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Iodine catalyst and heat are more important, in industry, something around 250 C with iodine is used for 24h, and it is done. Wash with sodium
carbonate (hydroxide?) sol. and it is ready. I added about 0.5% weight of I2 as a catalyst.
I never asked for this.
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Magpie
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| Quote: Originally posted by elementcollector1 | I've been looking at Magpie's setup back on page 41 and I don't quite understand - why is the retort so insulated with cement? Can metal not do the
job (is it corroded / melted / etc.)? I'd like to try this myself on a smaller scale with a soup can, but I'm not sure that I should coat the insides
with cement (would regular cement instead of furnace cement make any difference?)
|
on page 40 you will see why I began using a cement lining.
This line of experimentation is fraught with hazards. Be sure you have adequate protection and ventilation.
Paint cans are very thin-walled. A soup can wall is probably a little thicker.
The single most important condition for a successful synthesis is good mixing - Nicodem
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elementcollector1
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I see. In that case, I'll line the inside with some cement that we have lying around, and see if that works.
The ignition temperature of 750 C should be no problem, but the vaporization of P4 and subsequent oxidation to P2O5 will be - should I flush the
container with argon?
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Magpie
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| Quote: Originally posted by elementcollector1 | I see. In that case, I'll line the inside with some cement that we have lying around, and see if that works.
The ignition temperature of 750 C should be no problem, but the vaporization of P4 and subsequent oxidation to P2O5 will be - should I flush the
container with argon? |
Portland cement has a lot of water of hydration. When heated to 750°C it will likely give off this water turning your P4 vapor into phosphine, PH3,
a poisonous gas.
Use of argon is not mandatory. The whole problem of making P this way is P4 vapor containment, and condensation of the P4 vapor, while at the same
time excluding water vapor and oxygen.
I'm not trying to discourage you but it is really not a project for a beginner with improper equipment when done on the scale of a few grams or more.
[Edited on 6-6-2013 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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elementcollector1
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Is it possible to heat the Portland-cemented crucible without anything inside, as to get rid of any water of hydration?
I'm not too thrilled about playing with phosphorus, as I've heard the stories. I'll do my best to be careful.
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aliced25
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Heat it empty to cure it, while it is green it will give off water, when it is fully cured it won't. Portland Cement is probably not the best
heat-shield, but it has the benefit of availability.
From a Knight of the Realm: "Animated movies are not just for kids, they're also for adults who do a lot of drugs." Sir Paul McCartney
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12AX7
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Portland cement decomposes at 750C or so -- it's the water of hydration that sticks it together. Use something refractory, like a calcium aluminate
cement (if available), or furnace cement (a sodium silicate binder with, I believe, silica/clay base) diluted with porous refractory fill (sand, grog
(crushed fired clay), etc.).
Tim
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elementcollector1
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What about a mix of Plaster of Paris and sand?
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virgilius1979
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Excuse me if this was already discussed, but could Na reduce P4O10 to elemental P and Na2O ? because P4O10 is much cheaper than white P, and I could
produce Na from NaOH...
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Nitro-esteban
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Phosphorus is soluble in toluene so maybe it could be obtained by electrolysis of a phosphate using toluene as a solvent.
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elementcollector1
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Where's your reference for this (not to be picky, just interested if it's true), and what phosphorus salts may be soluble in toluene?
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