> >Message text written by Peter Marshall
> >>I wonder if the exact composition of ferric ammonium citrate may depend on
> >the
> >method of making it. The brown and the green forms have different formulae
> >in
> >the books of course.
> ><
> >
> >Peter
> >
> >How do you make it ?
> >
> >Terry
>
> From my text database (InfoSelect which I highly recommend BTW) with no
> attributions:
>
> >Dissolving freshly precipitated ferric hydroxide in a solution of ammonium
> >citrate in the correct proportions, then evaporating is supposed to
> >produce the brown version. Perhaps the green version could be produced
> >by using an excess of ammonium citrate.
>
> My guess is that the green variety in precipitated out of a strong ammonia
> hydroxide solution. I'd try (but don't do this at home kids) putting ferric
> sufate in ammonium hydroxide it will hydrate, add the ammonium citrate and
> it may form a green precipitate, which could then be filtered removing the
> sulfur compounds. Just a guess and guessing in chemistry is dangerous.
> Most people would not get beyond the strong ammonia part with out serious
> equipmen t however.
>
>
> Dick Sullivan
>
The brown form can be made by dissolving freshly prepared ferric hydroxide in
excess citric acid and neutralising with ammonia.
I suspect to get the green form would need excess of citric acid and less
ammonium citrate, but it isn't in any of my reference books here. Perhaps
someone with easy access to a chemical library could do a search?
Peter Marshall
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