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Re: Shelf life of Flourish/Substrate iron

Steve wrote:

[snip]
> I would like to see someone make a calibration test of several
> Fe test kits using precisely weighed amounts of chelated Fe in
> distilled water. Several people can participate in this study; in
> fact, the more people involved, the better ....

Steve, I have recently spoke with Sechem regards the Flourite soil substrate
product which is a calcined clay product.  It has iron ... ferric iron. They
also
mentioned their Flourish and Flourish Iron fertilizers contain non-chelated
iron ... ferrous gluconate.  Subsequent to the conversation I posted the
message
below which I had hoped could be answered by some of the chemists on the
list as I felt the interest in Iron and Iron test kits is always popular
here as indicated
also by the current thread.

------------------- original message -------------------
Hi,

I have just got off the phone with Seachem technical support and been
informed that the Iron supplied in their Flourish line of products is non-
chelated, that it is ferrous  gluconate, and that this makes it better than
many other iron supplements which are chelated.

I was then reminded of the many posts on the APD which indicate that
neither the Lamotte or Hatch test kits test for chelated iron. Yet most of
us get measurable numbers from these test kits.

Could one of more chemically inclined APDers remove some of the
confusion surrounding the statements the test kit manufacturers are
making versus the results which we obtain in practice?  I have read that
it is possible the test kits can still be accurate, that the measurements
we get are as a result of the iron comming unchelated.

But if the iron did become unchelated, it raises the question, how fast and
how completly was it unchelated by the time we test it? (did it measure all
the iron)

Additional questions regards iron I have:
  1)  in measurements I have made using Dupla drops in a
       bucket of tap water, the iron levels remain stable
       over the period of a period of a week.  This seems to
       contradict what I have read that iron is unstable. Any
       insight?
2)   Does anyone know if the Dupla products are
       chelated and by which chelate?
3)   Is there really any benefit to non-chelated iron
       versus chelated ferrous iron?

Christopher Coleman
christopher.coleman at worldnet_att.net