megalomania
August 31st, 2002, 05:40 PM
For the past two months I have had a solution of magnesium sulfate under constant electrolysis in my flowerpot and plastic bucket setup. While I have done this before, I have obtained a most peculiar black liquid. I obtained, as expected, much magnesium hydroxide precipitate on the outside of the pot. On the inside there should be not but sulfuric acid and excess magnesium sulfate. By letting it go for so long I was hoping for exhaustive electrolytic reduction of all of the magnesium sulfate, but I believe once the concentration goes below certain threshold you get plain water electrolysis.
Anyway, the sulfuric acid is very very black. I used carbon electrodes, and while I did lose some, I can account for much of the material. I filtered the liquid to remove any carbon residue, and then I checked a sample in a test tube under a strong light to check for turbidity, of which there was very little.
The black solution itself is pure black, like oil black. I held a flask filled with 1 L of the solution up to a very strong light, which did not penetrate at all. Even a small sample in a test tube under such a light is quite dim. Could there be some sort of reaction going on between the sulfuric acid? A sample tested with sodium bicarb did result in considerable effervescence, and a field pH test (as all I have are test strips) indicated a pH of between 1 and 2.
I wonder if it is possible the black may be highly divided particles of carbon from the electrode. I still find that rather difficult to accept because I can account for most of the lost electrode carbon. The only other contaminant may be a little copper sulfate from the copper cladding of the electrode, but then there is very little of that and the solution was already black way before my electrode slipped that far in (I needed the stand, and I actually electrolyzed my damn alligator clamp, grrr).
I was hoping for a little bit greater purity of sulfuric acid. Could it have been some insect or other organic matter getting in there and reacting with the sulfuric acid? My neutralized solution is actually a light brown, or possibly green (my color deficiency won’t let me distinguish) without a trace of black. That would seem to rule out a suspension. A good centrifuge would help right about now...
Anyway, the sulfuric acid is very very black. I used carbon electrodes, and while I did lose some, I can account for much of the material. I filtered the liquid to remove any carbon residue, and then I checked a sample in a test tube under a strong light to check for turbidity, of which there was very little.
The black solution itself is pure black, like oil black. I held a flask filled with 1 L of the solution up to a very strong light, which did not penetrate at all. Even a small sample in a test tube under such a light is quite dim. Could there be some sort of reaction going on between the sulfuric acid? A sample tested with sodium bicarb did result in considerable effervescence, and a field pH test (as all I have are test strips) indicated a pH of between 1 and 2.
I wonder if it is possible the black may be highly divided particles of carbon from the electrode. I still find that rather difficult to accept because I can account for most of the lost electrode carbon. The only other contaminant may be a little copper sulfate from the copper cladding of the electrode, but then there is very little of that and the solution was already black way before my electrode slipped that far in (I needed the stand, and I actually electrolyzed my damn alligator clamp, grrr).
I was hoping for a little bit greater purity of sulfuric acid. Could it have been some insect or other organic matter getting in there and reacting with the sulfuric acid? My neutralized solution is actually a light brown, or possibly green (my color deficiency won’t let me distinguish) without a trace of black. That would seem to rule out a suspension. A good centrifuge would help right about now...