rabidmonkey - 11-12-2010 at 22:45
So I know that you can get sulfuric acid and copper metal by electrolyzing aqueous copper sulfate. And i just found about a pound of magnesium sulfate
(epsom salt) in my basement. Can you get sulfuric acid from magnesium sulfate in a process similar to the copper sulfate method?
hissingnoise - 12-12-2010 at 03:59
I think Mg is probably too reactive to properly plate out of solution, but electrolysis of MgSO4 using a Cu anode will form CuSO4 and Mg(OH)2.
The hydroxide can be filtered out of the solution, leaving dissolved CuSO4!
blogfast25 - 12-12-2010 at 07:43
No. Bar heating the MgSO4 to insane temperatures to cause dissociation: MgSO4 ---> MgO + SO3 and capturing the SO3 in water, MgSO4 is no route to
H2SO4.
If sulphuric acid is desired for home experiments, get a drain cleaner: some are 50 % H2SO4, some are 95 - 98 % H2SO4. Familiarise yourself with its
properties before cracking open a bottle: it's pretty corrosive stuff...
hissingnoise - 12-12-2010 at 08:13
Capturing SO3 requires H2SO4 as absorber because contact between SO3 and water just produces a mist of H2SO4 which is very difficult to condense.
not_important - 12-12-2010 at 11:05
And you'll get little SO3 from disassociating MgSO4 as the temperatures needed are high enough to also disassociate the SO3 into O2 and SO2; although
you could feed that into a contact process rig.
Formatik - 12-12-2010 at 15:53
I've used magnesium sulfate to get to Na2SO4 by mixing it (aq.) with NaOH, filtering the Mg(OH)2 and crystallizing and drying the Na2SO4. Then mixed
the Na2SO4 with excess conc. HCl to get H2SO4 in solution alongside NaHSO4, NaCl. Shaking, then separation of solids leaves H2SO4 and some NaHSO4 in
the HCl solution. Boiling off the HCl until white dense fumes forms leaves behind H2SO4 and NaHSO4, which solidifies if cooled. The H2SO4 can be
purified by distillation. I wouldn't use this though because it takes a lot of energy to remove HCl and especially to distill H2SO4 (I'm not doing
that again, at atmospheric pressure of all things). Through that way, I was also only able to convert a bit under less than half of the sulfate of the
sulfate portion of Na2SO4 to sulfuric acid. There are two threads on it on this forum somewhere.
[Edited on 13-12-2010 by Formatik]
bbartlog - 12-12-2010 at 20:01
I've done this. You need a membrane to separate the anode and cathode compartments of your electrolysis setup (so no, it's not like the copper sulfate
method, which I believe uses no division).
Mg(OH)2 will form at the cathode (I used stainless steel, but many cathode materials should work), and needs to be removed every so often as it
precipitates and clogs things up. The anode needs to resist sulfuric acid; I used lead, which develops a coating of PbO2 under these conditions.
However a properly applied PbO2 coating would be much better as the one that develops this way keeps flaking off over time.
In time you end up with an anolyte solution that is a few % H2SO4, which can then be concentrated by boiling off the water. You will still need to
separate the remaining MgSO4 (and I ended up with FeSO4 contamination from my terra cotta membrane).
Frankly it's a pain in the neck and I don't regard it as a practical route to H2SO4. I think I ended up with ~10ml of very contaminated H2SO4 after
quite a few hours' work.
symboom - 7-5-2011 at 19:22
its a good thought. ive tried this the problem is you end up with contaminated sulfuric acid with magnesium sulfate. if you don't need necessarily
pure sulfuric acid for example making hydrochloric acid (magnesium sulfate is inert in the processes) and making nitric acid with sulfuric acid.
AJKOER - 10-5-2011 at 11:32
Hi:
Here is an idea. First, prepare a Zinc salt (you should find sources of zinc around the house and I will not recommend using a US Penny, which is
copper plated over a Zinc core). Zinc Carbonate (from ZnO + CO2), for example, will react with Epson Salts (MgSO4) forming ZnSO4.
MgSO4 + ZnCO3 = ZnSO4 + MgCO3
in the presence of water, you may get the soluble Magnesium Bicarbonate. Alternate, use Zn(OH)2 derived from dissolving Zn in Acetic acid (slow
process) and H2O2. Then add NH4OH causing a white suspension of possible nano-particle size Zn(OH)2. Then, add Epson Salt:
MgSO4 + Zn(OH)2 = Mg(OH)2 + ZnSO4
Second, heat the ZnSO4 which decomposes upon being strongly heated (quicker with a reducing agent) as follow:
3 ZnSO4 -----> 3 ZnO + O2 + 2 SO2 + SO3
Capture the gases in water plus a little H2O2:
SO3 + H2O ----> H2SO4
SO2 + H2O2 --> H2SO4