Murexide
Hazard to Self
Posts: 51
Registered: 1-12-2018
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Fertiliser Iron Sulphate (Ferrous Sulphate)
Ferrous Sulphate can obtained as a fertiliser in some stores. In my case, it is claimed to be 100% Iron (II) Sulphate heptahydrate as written in the
msds. It comes in a pale brown product, which is rather suspicious as green-blue crystals are expected for the heptahydrate.
Upon addition of dilute sulfuric acid and water in attempt to dissolve it, it forms a brown slurry which does not dissolve even upon strong heating
(or no heating - so oxidation isn't causing the problem). The consistency of the slurry is comparable to calcium hydroxide slurries.
I attempted to filter and recrystallise, through a coffee filter. Unfortunately, the unknown suspension filtered through. Using a slow quantiative
filter paper worked, but the drip rate was very slow, although crystals nice green crystals started to form in the filtrate. This should be the
heptahydrate. Vacuum filtration is an option, but generally not desirable for hot filtrations.
After cooling the slurry without filtering, it formed a solid green mass (which I thought was the heptahydrate). Unfortunately, upon stirring with
more acid and water, it immediately returned to the brown colour.
It seems like the other options of obtaining the ferrous sulphate are dilute sulfuric acid and iron powder, or iron powder and copper sulphate. I have
access to all the materials required for both methods, but it seems rather inconvenient/unecessary considering the purchase of iron sulphate was made,
to avoid such complications!
The fertiliser in question is "Manutec Iron Sulphate, soluble corrective elements"
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Murexide
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Posts: 51
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Upon reading some more, it looks like oxidation to iron (3) species is the problem. I will check to see if any iron sulfate still available for sale
is the blue green advertised, otherwise reduction of filtrate with iron powder then recrystallisation. If that fails, then the 30% sulfuric acid route
should guarantee success, albeit low yields
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RogueRose
International Hazard
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Registered: 16-6-2014
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Quote: Originally posted by Murexide  | Upon reading some more, it looks like oxidation to iron (3) species is the problem. I will check to see if any iron sulfate still available for sale
is the blue green advertised, otherwise reduction of filtrate with iron powder then recrystallisation. If that fails, then the 30% sulfuric acid route
should guarantee success, albeit low yields
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I has similar problems with FeSO4, it seems like an odd beast. My first attempt was making it from very old nails and H2SO4 (maybe some H2O2 as well).
I got the emrald crystals and placed it in a plastic Prego bottle (seals air tight) and there was proably a little H2SO4 left on the surface, not a
lot b/c I washed it and the remaining liquid that didn't crystalized should have kept the remaining H2SO4, I would think.
After about 6 months much of the surface had turned an orange-ish brown. I think I posted pics maybe 1-2 years ago, I'm sure a search with my name
and FeSO4 will show pics.
I then boiled down all the crystals and got a white powder, maybe very slight green/brown/yellow. I beleive it was anhydrous and before it boiled down
the solution was dark brown.
upon adding water I got a gross looking dark brown/green (careful to add only 5% excess water to get all into solution) and eventually I had the
purest, greenest crystals I've seen of FeSO4.
I've played around more with them and I've gotten all strange colors. Now be careful not do get Fe2(SO4)3 Iron III Sulfate
https://en.wikipedia.org/wiki/Iron(III)_sulfate
This will happen by addig H2SO4 to FeSO4 (especially with H2O2 Mixed in) I have no idea what it can be used for, FeSO4 can be fun and is good for
many things, Iron III, not so much from what I have seen.
If I were you, I would heat to anhydrous (just below 600F) and then add water. It takes it's time dissolving, maybe a couple days even with stirring,
but if you end up with a pure green solution, then you know you have Iron II sulfate.
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