Re: Chelating stuff

> From: Gerard van Klaveren <klaveren at bart_nl>
> Last issues of the APD contained much messages about 
> chelating chemicals such as EDTA, DTPA, HEEDTA(?).

Here is a message:From: franc at golden_golden.net
> Date: Tue, 9 Apr 1996 00:57:29 +0000
> Subject: Re: Diethylene triamine pentaacetic acid
> On  Sun, 7 Apr 1996 19:35:28 -0500
> Paul Krombholtz wrote....
> > Subject: Re: EDTA photodegredation
> >
> > When I was growing aquatic plants in algae-free culture back around
> > 1966-68, I noticed that I had a precipitate in flasks of nutrient solution
> > plus iron EDTA that had been exposed to light, but no precipitate in
> > identical flasks kept in the dark.  However, enough iron stayed in solution
> > to grow the plants satisfactorily.
> >
> > Currently, I am using iron DPTA, (diethylenetriaminepentaacetic acid),
> > which appears to stay in solution a lot longer.  CIBA-Geigy, agricultural
> > chemicals division,  makes it, but it is hard to find in your average
> > garden store.
> >
> Yes. There are three chelates commonly used to sequester trace metals.These
> are: EDTA        ethyline diaminetetra acetic acid
>      DTPA        diethylene triamine pentaacetic acid
>      EDDHA     ethilene-diamine dihydroxyphenyl acetic acid
> EDDHA  and DTPA chelate iron only. EDTA associates with copper, zinc,
> manganese, bivalent iron(Fe++), and trivalent iron(Fe+++). All three chelates
> are less stable at higher pH than lower pH. The stabilities of all three are
> also adversly affected by light.
> FeEDDHA is by far the most stable at higher alkalinities and it is the
> preferred form where there is a  high concentration of  calcium bicarbonate.
> FeEDDHA is expensive and  often difficult to obtain. It is very efficient and
> only a fraction is needed to do the job as compared with FeEDTA. The company
> that sells it is CIBA-GEIGY Corp, Box 11422, Greensboro, NC 27409. But they
> won't sell you just a spoonful. :-).
> FeEDTA is at least stable. At pH above 7.0 80% will decompose after two weeks
> It is used commonly because it is cheap and because it is a good product to
> chelate all four trace metals.
> To maintain greater iron solubility FeDTPA is often added to FeEDTA. former
> is slightly more stable than latter. When added together a boosting effect
> occurs and the mixture is as stable as FeDTPA alone.
> By the way Paul where did you get it ??
> Further reading... P. Fisher Stability of various forms of chelated iron in
> nutrient solutions of different pH values ISOSC Proceedings 6th International
> Congress on Soilless Culture  1984, pp. 225-233
> Franc Gorenc                           franc at golden_net
> Kitchener, Ontario                  http://www.golden.net/~franc
> Canada

To answer your other questions, no I do not believe extra DTPA or EDTA
will inhibit plants ability to absorb and use Fe however, I am not an
expert on this so I hope someone will give a more definitive response to

Steve Pushak            spush at hcsd_hac.com     Vancouver BC Canada