Sciencemadness Discussion Board

Extracting Magnesium from Wood Ash

Sprotz - 31-5-2020 at 15:44

Can someone tell me how to go about extracting Magnesium from Wood ash and separating it from calcium, and other metal oxides present ?

ThoughtsIControl - 31-5-2020 at 19:22

You could just rinse, filter, repeat a few times. Calcium and some other contaminants you have will be water-soluble. Magnesium is insoluble. By rinsing and filtering, it should be easier to sift through everything. Magnesium is quite shiny. Plus, it's paramagnetic. So there will be a weak attraction towards magnets if you wanted to sift through with one.

Hope this helps! :)

j_sum1 - 31-5-2020 at 19:59

Quote: Originally posted by ThoughtsIControl  
You could just rinse, filter, repeat a few times. Calcium and some other contaminants you have will be water-soluble. Magnesium is insoluble. By rinsing and filtering, it should be easier to sift through everything. Magnesium is quite shiny. Plus, it's paramagnetic. So there will be a weak attraction towards magnets if you wanted to sift through with one.

Hope this helps! :)
That's perhaps a wee bit snarky here.
The point being made of course is that Mg won't be found in wood ash. Magnesium cojmpounds will be. And isolating them will be a pain A lot more trouble than it is worth.

  • Firstly you have a mixture of cations. K will be dominant. I would anticipate that Mg compounds will be in very low proportions.
  • Secondly, you have a decent mixture of anions. That makes the isolation chemistry difficult.
  • Thirdly, you will find it difficult to separate out Mg from other ions that behave similarly. Even finding a wet chemistry metho to distinguish Mg2+, Ca2+, Zn2+ and Al3+ is tricky. But that would be my start point. (There are good YT vids on this.) Then take the principles employed and use them to isolate your Mg compound.

    Get set for some disappointment. :(

    Boffis - 1-6-2020 at 01:46

    I can't imagine a more ridiculous starting material than wood ash for the isolation on magnesium salts. The Mg content of wood ash is very low.

    There are numerous much better sources of magnesium than wood ash; epsom salts, various magnesium hydroxide and basic carbonate rich preparations for gardening/horse etc, magnesium rich rocks like dolomite, serpentinite, etc. Just down the road from where I am now they used to extract magnesium from sea water. The process may be of interest to you since it offer a method of separating Mg from most other common cations in sea water. They used to add saturate lime water to the sea water. This precipitates the Mg as a basic carbonate which was simply settled out and finally dewatered in a filter press. I'm sure this route could be used to extract Mg from most things if modified carefully.

    If you are trying to prepare Mg metal the process is going to be several orders of magnitude more difficult.

    Sprotz - 1-6-2020 at 10:06

    Yes, the intention is getting magnesium metal. I know the method of getting magnesium from salt water, I also know that Magnesium is found in Laxatives, I was just checking if wood ash was a good source. So there is no easy way to get magnesium metal? The easiest possible way I heard is by reduction of molten magnesium chloride by potassium metal at 700 C, and there is an easier way recently developed that uses a lower temperature but the method is proprietary and they won't divulge the secret.

    Mateo_swe - 1-6-2020 at 11:33

    Is there any reason why you cant just buy the Magnesium metal?
    Its not expensive, in a fast ebay search i found 99.99% Mg rods 9cm tall, 16mm thick going for 2 Euros per rod.
    Or are you doing this for the experience of extracting a metal from a common source?

    G-Coupled - 1-6-2020 at 13:17

    Isn't Magnesium contained in Chlorophyll? Maybe green leaves might be a better source of Mg than wood is.

    SWIM - 1-6-2020 at 13:48

    If you're doing this to make magnesium from a natural source as opposed to from some prepared chemical then maybe you can find or buy some magnesium containing mineral for your project.

    Much higher yields for the extraction.



    The tough part will be reducing it to metal I bet.

    How about dolomite?
    https://m.media-amazon.com/images/M/MV5BMDc3MGIyZjktNGRhNS00...

    Oops, typo.
    https://mahaveermineral.com/wp-content/uploads/2017/02/dolom...

    [Edited on 1-6-2020 by SWIM]

    DraconicAcid - 1-6-2020 at 14:11

    Quote: Originally posted by G-Coupled  
    Isn't Magnesium contained in Chlorophyll? Maybe green leaves might be a better source of Mg than wood is.


    I doubt it. The amount of magnesium in chlorophyll is very small.

    https://www.researchgate.net/figure/Chemical-composition-of-...

    ThoughtsIControl - 1-6-2020 at 17:05

    "The easiest possible way I heard is by reduction of molten magnesium chloride by potassium metal at 700 C, and there is an easier way recently developed that uses a lower temperature but the method is proprietary and they won't divulge the secret"

    Using thermite would be an easier method to reach those temperatures as compared to a wood fire. However, I'm sure there are alternatives since thermite is dangerous.

    draculic acid69 - 1-6-2020 at 22:16

    It's a terrible starting material. potassium and calcium could probably be isolated but I don't think magnesium could be recovered in any more than tiny amounts. If u poured a packet of Epsom salt over a wood fire and then worked up the ashes u might end up with some mg oxide which with carbon might be reduced to the metal.but it's a terrible way to go.

    Sprotz - 2-6-2020 at 01:09

    Quote: Originally posted by Mateo_swe  
    Is there any reason why you cant just buy the Magnesium metal?


    I can buy it if need be but I just want to gather knowledge on how to make it and other chemicals ourselves in case of some future survival situation or in case the market changes.

    Fery - 2-6-2020 at 02:08

    Sprotz - when you want to extract something from wood ash in survival situation it is K2CO3 which is used for producing soap.

    Mateo_swe - 2-6-2020 at 12:18

    I seem to remember something about a guy trying to extract nitrates from the soil where many people had urinated over a long timeperiod.
    Some nitrate would be useful in a survival situation as it can be used to make explosives, aid in starting a fire and many other things.
    Not so nice to process the pee saturated soil though.

    metalresearcher - 2-6-2020 at 12:26

    Forget it. Mg is harder to isolate than K or Na.