jan1234
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impurities in iron(ii) sulphate on industrial scale
hi!
since my company get's their iron(ii) sulphate from a vendor who gives information on the heavy metal content and only specifies "90% iron, we are
wondering what the other 10% could be.
trace amounts of heavy metals, dioxines etc can't make up 10% of the whole. we're guessing SiO2, CaCO3 (maybe CaCl2 or CaO), MgO, MgSO4, MgCO3 and
TiO2 (the titanium is coming from the process itself, since titatium is used according to the vendor - no idea if it's just the vessels or some
reaction to get the monohydrate.
so we are thinking what makes up 10% of the mass of the 100s of tons we use every year?
we sent a sample to an extern lab, but since we only have guesses, we didn't really know what we should have had looked at.
maybe someone out there know's about the production of sulphate on large scale?
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Sulaiman
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https://en.m.wikipedia.org/wiki/Iron(II)_sulfate
see Production and Reactions section
and since you mentioned titanium dioxide, manganese and zinc seem to be common in the ore
https://en.m.wikipedia.org/wiki/Ilmenite
CAUTION : Hobby Chemist, not Professional or even Amateur
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jan1234
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Well thank you!
I googled 'iron sulphate impurities on industrial scale' and the like, but simply looking up iron sulphate didn't come to my mind /o\ shame on me. We
sent samples to a lab to look for some of the candidatws. I will report when the results are in 
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KoiosPhoebus
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I wonder if by 90% iron they mean 90% iron(II) specifically. After all, the
most common assay for ferrous sulphate purity is the permanganate oxidation assay, which measures how much MnO4- is reduced by a
specified mass of the sample. Iron(III) would not consume permanganate in such an assay and hence would be left out of the amount of iron found.
It's common for samples of ferrous sulphate to oxidise to basic ferric sulphate when exposed to moist air, so Fe(III) may represent a proportion of
the remaining 10%. Hence people using ferrous ammonium sulphate (aka "Mohr's salt") as an alternative source of Fe(II) ions, as the slight acidity
contributed by the ammonium sulphate renders the double salt more stable.
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