Re: Dechlor and chelation

> bacterial growth in mains water distant from the treatment plant.
> The timeframe that I have heard for spontaneous breakdown is 13 days
> to three months.
> Sodium thiosulfate is used to deal with the chlorine releasing the
> ammonia to become breakfast for your hygro. The amount required
> depends upon pH -the higher the pH, the less you need. I use two to
> three times the recommended level for chlorine. It's cheap.
> - --
> Dave Whittaker                       ac554 at FreeNet_Carleton.CA
> Gloucester, Ontario                  dwhitt at magmacom_com
> Canada

Dave, what is the reccomended level of Na thiosulfate for chlorine?  How 
much is needed to dechlor water that comes out of the tap at pH~8?
How does Na thiosulfate affect micronutrient concentrations?

> ------------------------------
> From: psears at NRCan_gc.ca (Paul Sears)
> Date: Tue, 2 Apr 1996 10:58:26 -0500 (EST)
> Subject: Re: micronutrients and EDTA
> > From: Paul Bucciaglia <paul-b at biosci_cbs.umn.edu>
> > 
> > 
> > 1) I currently use Tap water conditioner, which claims to dechlorinate 
> > and 'remove heavy metals'.  How long is this active after addition to tap 
> > water? 
> 	What is in it?  Long-chain amines?

Nothing listed on the bottle of 'Tap Water Conditioner' ((Aquarium 
Pharmaceuticals).  Recommended dose is 1 drop/gal for 'detox. heavy 
metals' and 1/2 tsp. / gal to 'remove chlorine from chloramine'.  I use 
it at 2 drops/gal.

> > Will this result in a serious reduction of micronutrients (Zn, Mo, 
> > Mn) added after dechlorinaiton?  
> 	Cu, Mn, Fe, Zn:  quite possibly - they are all there as positive
> ions, which could well be complexed by the active ingredients of a
> conditioner.  EDTA complexation of these ions may slow or prevent
> the process.

This is what I was getting at.  I guess if these micronutrients are 
chelated, they would become available slowly as the EDTA was degraded, as 
is the case for Fe.  Is chelation necesary to maintain Cu, Mn, and Zn 
available to plants?  I guess since many aq. 
plant fertilizers contain chelated Fe plus these micronutrients its OK if 
some become partially chelated by exchange of Fe for anothre micronutrient.

> 	Mo, B:  probably not - they are there as oxo anions, not likely 
> to be complexed by the same things.

OK, so Mo complexes with O2 and is therefore not chelated.  Is this the 
form that plants take up? 

> > Any dechlorinators which will not interfere 
> > with micronutrient fertilizers?   I remember hearing that Na thiosulfate 
> > was  an effective 
> > dechlorinator--does it work on choramines, and at what concentration?
> > 

Hopefully Dave W, will fill us in....

> 	Mo and B will not be chelated (see above).  The chelation of iron
> is usually done to stop its precipitation as the oxohydroxide, but the
> chelation reaction is an equilibrium, so the complex will come apart, (slowly)
> and other ions in solution can then grab the EDTA.  Even calcium will
> do this, so the Fe chelate is not likely to reform before the iron
> precipitates out.  As far as I know, all the positive ions we use form soluble
> chelates.  I have made them in solution without problems.
> 	Chelation is not a _permanent_ answer to iron precipitation. 

So mixing Fe-EDTA with other positive ions can cause precipition of Fe.  
I guess if you don't see it come out of solution, then the concentration 
of the mix is not too high. Most tissue culture recipes have the Fe-EDTA 
as a stock solution separate from other micronutrients, which is why I'm 
wondering about all this.  I guess these stocks must be at a higher 

> Paul Sears     Ottawa, Canada
> ------------------------------

thanks for the reply.

paul bucciaglia