!!!!!!!, as also boeuf bourguignon can fizz on adding the right wine
>Do we need separate chelating agents to rid the print of both the residual iron
>and potassium salts and is EDTA tri-sodium salt the most effective.
>
>Terry King
this is a very hard question to answer and I am in the middle of finding
out some more about this. Looking up information about EDTA tells us
EDTA: (HOOCCH2)2 NCH2 CH2 N (CH2COOH)2
ethylene-diamine-tetra-acetic acid
pfoowee this is a mouthfull,
as you can see it is a symmetrical molecule which is capable of
"encapsulating - catching" other stuff which can then be washed away. One
mole EDTA will react with one mole of metal ion. In an alcaline environment
it is NOT capable of binding Fe III and other metal III valencies. The
optimum binding capacity is strongly dependant on the pH, the chelating
properties of EDTA will be anulled by chlorine delivering and oxidating
agents.
- the visible ironsalt(s) = "rust" (Fe2O3) are called ferri-salts, the Fe
II is called ferro and in general not visible (or better without visible
color). There are two forms of iron: II and III: they have different
valencies [II and III] and will therefore bind in a different way to other
elements. So here might be the beginning of the answer why EDTA in some
formulations is not capable of removing the ironsalts.
Oxalic acid ( HO2 CCO2 H ) is used to remove iron stains from textiles
(this will damage cellulose though, also it is very poisonous and harmfukll
to the body). The salts are called double salts since the acid contains two
COOH groups and can therefore react with two metal ions. My limited
knowledge of chemistry suggests that in behaving so the FeII salts of
oxalic acid (invisible) can react and form ferro (visible) salt(s) this
might be the source of the staining (??).
Just some information to confuse us all a little more. Any bell ringing
with chemists amongst us? please let us know.
still looking further,
Bas van Velzen
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