Any phosphorus in fertilizer is present as P (+V), so as P2O5 in its various forms (mainly PO4(3-), HPO4(2-) or H2PO4(-)). No “PO4”.
Brown precipitate point to Fe (+III), precipitating as Fe(OH)3.2H2O (red-brown). Fe (+II) readily oxidises in the presence of air:
4 x [Fe2+ === > Fe3+ + e-]
O2 + 2 H+ + 4 e- === > 2 OH-
4 Fe2+ O2 + 2H+ === > 4 Fe3+ 2 OH-
So even if you started with Fe (+II) it looks like you ended up with Fe (+III).
Did you stir during addition of NaOH? Fe(OH)3 is very insoluble and local points of higher pH would precipitate it.
What’s your basis for the 8 g claim?
MoO: you mean molybdenum oxide? What source?
[Edited on 24-7-2011 by blogfast25] |