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Author: Subject: Extracting magnesium metal from its salts
plasma
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[*] posted on 20-5-2002 at 19:00
Extracting magnesium metal from its salts


Is it possible to extract magnesium from (MgCl) or powderize aluminum with sulfuric acid ?

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[*] posted on 20-5-2002 at 19:01


You would have to melt the MgCl2 and apply electricity to the molten salt to extract the magnesium. You can't make aluminum powder from aluminum and sulfuric acid. You can make aluminum powder out of aluminum foil with a ball mill and patience.
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[*] posted on 20-5-2002 at 19:02


How do the companies make it?
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[*] posted on 20-5-2002 at 19:02


How do I get MgCl to become MgCl2, does it happen when it meltes ?
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[*] posted on 20-5-2002 at 19:03


I'm so sorry for that stupid question, I will have to think before I write (I usually don't do that :))

Sorry
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[*] posted on 20-5-2002 at 19:03


I tried melting the salt and putting a lead anode and a lead cathode into the liquid. I used 7,2 volts and 2,5 amps. After 15 minutes nothing had happened so I stopped because I tought it was not enough amps.
What are the running times and how much amps/volts should be used for extracting the magnesium in 100g MgCl2 ?

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[*] posted on 20-5-2002 at 19:04


No chlorine gas was given off at all? Perhaps the lead is reacting with the chlorine forming PbCl2; and the magnesium metal formed is reacting with atmospheric oxygen and nitrogen forming MgO and Mg3N2. If the above actually was happening, the only change you would see is that the molten MgCl2 would slowly solidify. Make sure that the molten MgCl2 that you're electrolyzing is not coming in contact with atmospheric oxygen or nitrogen.



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plasma
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[*] posted on 20-5-2002 at 19:04


No chlorine gas was given of and the liquid (melted MgCl2) solidified slowly. To day a liquid had came out of the plates of the hardened MgCl2, what can this be ? I must admit, I did melt it in free air and it was also electrolyzised in free air. Maybe that is the reason for the bad results ? Is a vaccumk needed ? I still wonder how many amps/volts are needed.

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[*] posted on 20-5-2002 at 19:05


Check to see if the lead electrodes are corroded. If they are not corroded, then the reason for the bad results is exposure to atmospheric oxygen and nitrogen. A vacuum would be nice, but it isn't necessary. You could make sure that the molten MgCl2 that you're electrolyzing only comes in contact with carbon monoxide (sold as MAPP gas at hardware stores, it's a blow torch fuel). As for the liquid, I suspect it is water... I can't imagine what else it would be.
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[*] posted on 20-5-2002 at 19:05


Yes, the lead electrodes is erroded. CO2 would work instead of CO right (I have 15 litre bottles of it)? I still don't know how many amps/volts to use.

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[*] posted on 20-5-2002 at 19:06


CO2 cannot be used instead of CO; the CO2 will oxidize the magnesium metal.

Mg + CO2 + heat --> MgO + CO

The CO will not oxidize the magnesium metal.

The electrodes being corroded confirms my theory that the lead is reacting with the chlorine formed. I believe that the positive electrode should be the one that is the most corroded. Look into getting carbon electrodes. As for how much current to use: use as much as possible. The more, the better. There isn't a such thing as too much current in electrolysis (unless you're causing temperatures to get too high and boil a solution that is being electrolyzed).

I suggest making sure that you don't have a hydrate of MgCl2. If it is MgCl2*6H2O, then it will release some water at around 100C, becoming MgCl2*4H2O. It would be a good idea to check the specific gravity. Grind up some of your MgCl2 into an ultrafine powder. Mass a graduated cylinder. Fill up the graduated cylinder with 10mL of your MgCl2 (it should be highly compressed). Subtract the mass of the empty graduated cylinder from the mass of the graduated cylinder containing 10mL of your highly compressed MgCl2. Divide that number by 10. The resulting number is the specific gravity of your MgCl2. The specific gravity of pure (non-hydrated) MgCl2 is 2.32, for MgCl2*6H2O it is 1.56. The melting point of non-hydrated MgCl2 is 708C.




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[*] posted on 20-5-2002 at 19:06


The bag of MgCl2 says that it contains 70-100% MgCl2. If it had been MgCl2.6H2O it would only contain 46,5 % MgCl2. I am pretty sure it is pure MgCl2. CO sounds like a dangerous gas (flammable/explosive), is there any other options ?

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[*] posted on 20-5-2002 at 19:07


I can't think of a less dangerous gas to use. The only alternative to carbon monoxide that occurs to me is a vacuum. Carbon monoxide shouldn't be that dangerous to use if you use it outside or in similarily good ventilation.



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[*] posted on 20-5-2002 at 19:07


Is car exhaust pure enough CO ?
Will the electrolysis work with a hydrate ?
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[*] posted on 20-5-2002 at 19:08


Sorry, but the answer is no to both questions. Somehow this slipped my mind though: you can also use hydrocarbon gasses, such as methane, ethane, propane, butane, oils, etcetras.



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[*] posted on 20-5-2002 at 19:08


Hydrocarbon gasses does not sound like a good alternative; most of the gasses you listed has a autoignition temperature lower than the melting point of MgCl2.
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[*] posted on 25-5-2002 at 12:28


Industrial preparation is as follows:
A mixture of MgCl2 with KCl or other alkali or earthalkalichlorides(to lower melting point) is electrolysed with graphite anodes and iron kathodes. The molten magnesium will float on top and can be removed by suction.

Alternatives stated by my chemistry encyclopedia are reduction with ferrosilicium, calciumcarbid and Al. I wonder how the last one can be possible, that should be an endothermic reaction. All these processes have to conducted under inert atmosphere. Remember that alot of metal and non-metal oxides are NOT inert with magnesium (H2O, SiO2 (sand!), CO2,...)
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[*] posted on 27-5-2002 at 04:23


Try having a small crucible upside down in the crucible in which you're melting the MgCl2. Have the cathode in the upside down crucible (make sure it is full of MgCl2, not air).
Then, during electrolysis, the Mg will collect in the small crucible, and won't come into contact with any air.
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[*] posted on 25-10-2002 at 00:30


I have some AlCl3 and i would like to make some Al poweder. I recall this recation can be used:

2AlCl3 (aq) + 3Mg (s) -> 2Al (s) + 3MgCl2 (aq)

Would electrolysing a solution of AlCl3 yield Al(OH)3 or AlĀ·(H20)7?

Ball milling Al-foil? HOW much patience :o is needed!?
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[*] posted on 25-10-2002 at 11:20


Quote:
2AlCl3 (aq) + 3Mg (s) -> 2Al (s) + 3MgCl2 (aq)


I believe that will fail in practice. Al is too reactive to form in aqueous media, either by displacement with more reactive metals or electrolysis. Note, however, that you can make zinc powder this way, starting with zinc chloride and aluminum foil.

Ball-milling foil is what is commonly recommended on rec.pyrotechnics for those who can't just buy aluminum powder, and you can find a good number of posts there (archived on Google Groups) about the topic. I believe that magnesium-aluminum alloys are considerably more brittle and easier to mill than either Al or Mg alone, so if you can obtain or make an alloy of the two metals, you could try using that as well.
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[*] posted on 26-10-2002 at 13:00


The simple fact the lead electrodes were still solid means the temp of the cell is less than around 350C, so it cant be molten anhydrous MgCl2.

Mg melts around 650C, so if you can drop the temp below that by using a eutectic mixture, the Mg will be solid and you can do without gas alltogether. I cant find what the KCl.MgCl2 eutectic melts at.

For most people its easier to find something made of magnesium and grind it down.
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[*] posted on 26-10-2002 at 23:46


The number of amps you use is entirely dependant on how much stuff you want to get. Volts? i would suggest an excess voltage; but if you wanted an exact figure, using standard reduction potentials, Mg(l)2+ + 2e- => Mg(l) -2.37 V. I never was very good at electro chem, so you'll have to get this seconded.

A back-of-the-envelope calulation suggests that 1010 C would just about do it for a 1 g sample of MgCl2, that's about 7 minutes at 2.5 amps.
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[*] posted on 27-10-2002 at 16:37
I think


MgCl2 anhydrous can also be electrolysed under some NaOH. If you try to melt MgCl2*6H2O ....... you'll end up H2O vapor and HCl gas and MgO. Anhydrous MgCl2 I think can only be bought in chem stores and preparing it from other Mg salts is a pain in the ass. Anyways even if you do get your hands on some ..... mix some KCl with it to make it melt at a lower temp. then once you have it molten ..... dump some KOH or NaOH on it ..... I don't think they mix. The OH forms a layer on top and when the mix is electrolysed the molten OH protects the Mg formed. Although the Fe cathode does corrode.



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[*] posted on 7-11-2002 at 23:56


Sorry for going OT once again but I think this is the best thread to post this question:
Ok, so Al powder can't be made this way:
2AlCl3 (aq) + 3Mg (s) -> 2Al (s) + 3MgCl2 (aq)

But zink can, so I guess ironpowder could be made this way or would i get Fe(OH)2 or some other unuseable form.
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[*] posted on 8-11-2002 at 00:26


I would think that you could get iron powder that way. Mechanical methods are cheaper and neater for iron, though. Also, depending on your reaction conditions, you may end up with a thick skin of iron metal instead of anything resembling powder.
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