Sciencemadness Discussion Board

Magnesium chlorate

Chemgineer - 24-1-2022 at 14:29

I am fairly sure i've synthesised magnesium chlorate.

I used bath salt grade magnesium flakes which stated magnesium chloride hexahydrate 100% on the bucket. I made up a 200ml saturated solution in a beaker and I made up double that amount in a bottle for topping up.

I electrolysed the solution with an MMO anode and a stainless steel cathode at 5amps. The problem with this salt is during electrolysis a layer of magnesium hydroxide builds up on the cathode and as this is insoluble it eventually prevents current flow as the cathode is completely coated. So I laboriously scraped the hydroxide off and stored it for future use.

A combination of electrolysis and heat means the liquid level drops fairly quickly so I kept topping it up and eventually added more than another 200ml of the saturated solution. Now as magnesium chlorate is roughly twice as soluble as the chloride I didn't expect to see anything until i'd added at least this much electrolyte.

After each run I cleaned the cathode and filtered the liquid through a coffee filter to remove excess hydroxide.

After a couple of days once filtered and and allowed to cool down I got some clear white spiky crystals formed in the beaker. I can't find much online about what shape magnesium chlorate crystals should be so I gave them a quick test. I put a very small amount on some foil and put a gas flame on it, it very quickly melted and water boiled and on cooling it solidified into a white mass. I then repeated heating with some sugar spinkled on top and this time the sugar seemed to puff up probably due to gas being released from the salt.

I'm now allowing the compound to dry in a beaker on a radiator in my lab.

9CWAI - 24-1-2022 at 21:12

To be certain try mixing it with charcoal or starch, it should oxidize (explosively if Wikipedia is to be believed) those relatively easily with heating. For purification it is soluble in acetone and chloride is not. If you want to make more to test it (I may try eventually) I would recommend finding a way to have your cathode vibrate to keep the hydroxide from coating it. Maybe use an "ultrasonic" bath?

mysteriusbhoice - 24-1-2022 at 22:21

Quote: Originally posted by Chemgineer  
I am fairly sure i've synthesised magnesium chlorate.

I used bath salt grade magnesium flakes which stated magnesium chloride hexahydrate 100% on the bucket. I made up a 200ml saturated solution in a beaker and I made up double that amount in a bottle for topping up.

I electrolysed the solution with an MMO anode and a stainless steel cathode at 5amps. The problem with this salt is during electrolysis a layer of magnesium hydroxide builds up on the cathode and as this is insoluble it eventually prevents current flow as the cathode is completely coated. So I laboriously scraped the hydroxide off and stored it for future use.

A combination of electrolysis and heat means the liquid level drops fairly quickly so I kept topping it up and eventually added more than another 200ml of the saturated solution. Now as magnesium chlorate is roughly twice as soluble as the chloride I didn't expect to see anything until i'd added at least this much electrolyte.

After each run I cleaned the cathode and filtered the liquid through a coffee filter to remove excess hydroxide.

After a couple of days once filtered and and allowed to cool down I got some clear white spiky crystals formed in the beaker. I can't find much online about what shape magnesium chlorate crystals should be so I gave them a quick test. I put a very small amount on some foil and put a gas flame on it, it very quickly melted and water boiled and on cooling it solidified into a white mass. I then repeated heating with some sugar spinkled on top and this time the sugar seemed to puff up probably due to gas being released from the salt.

I'm now allowing the compound to dry in a beaker on a radiator in my lab.


If you have problems with magnesium hydroxide just keep temps high and add HCl and pH control is very very easy using magnesium chloride because the hydroxide will act as a buffer.

5 amps is too low a current for this because im sure your MMO can handle much more current given the size of these run them at 200ma/cm^2 and run the cell at about 70C.

pH controlled cells are now possible in the amateur setting thanks to magnesium and calcium chloride addition to NaCl so it would make sense that you can do the same with pure MgCl2.

[Edited on 25-1-2022 by mysteriusbhoice]

unionised - 25-1-2022 at 00:54

Are the "magnesium flakes" very hygroscopic?
I'm wondering if they are actually sulphate.

In any case, how can you be sure you have not just regenerated the starting material (whether it's MgCl2 or MgSO4)?
You made a saturated solution, and evaporated off water.
What would you expect to happen when you cooled the resulting liquid?

Chemgineer - 25-1-2022 at 09:51

Quote: Originally posted by unionised  
Are the "magnesium flakes" very hygroscopic?
I'm wondering if they are actually sulphate.

In any case, how can you be sure you have not just regenerated the starting material (whether it's MgCl2 or MgSO4)?
You made a saturated solution, and evaporated off water.
What would you expect to happen when you cooled the resulting liquid?


It's definitely starting from magnesium chloride flakes, I put 20 deg C water in a 10ml test tube and when dissolving in it I got a temperature rise to 26 deg C.

[Edited on 25-1-2022 by Chemgineer]

Fantasma4500 - 21-2-2022 at 12:54

http://chemister.ru/Database/properties-en.php?dbid=1&id...

http://chemister.ru/Database/properties-en.php?dbid=1&id...

seems you might be able to get some vague result out of trying to dissolve the solid in ethanol
or- just do the regular chlorate test, HCl it.

i cant imagine magnesium chlorate not being hygroscopic

would probably be easier to do fractional crystallization, NaClO3 + MgCl2- i dont remember if they will react in this order however