bfrenock

Iron Calibration

7 posts in this topic

I have a Hanna Instruments HI721 Iron Checker.  I buy 5% chelated iron (Biomin).  Today I read zero ppm when I tested iron in my 1200 gallon system.  Checked twice.  So I added one ounce 5% chelated iron to 3 gallons of spring water (pre-tested this water and I've tested this water several times in the past and have never detected enough iron to show).  When I tested a sample of the 1oz/3G water, it showed 2.54ppm.  My assumption is that 5% iron is 50000ppm and adding one ounce to 3 gallons would dilute it 384 times (128 oz./gal.).  So I should have had a reading of about 130ppm, way over the scale of the instrument (it is 0-5ppm). So now I wonder if my calculations are in error, or is the iron tester in error, or is the chelated iron not really 5%?

My question: Does anyone use a calibration liquid for iron similar to pH calibration liquids to verify a tester?  

Thank you for your time.  Have a great day!

Bob 
 

Cecil likes this

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Hi Bob

Welcome to APN/HQ

1 hour ago, bfrenock said:

My assumption is that 5% iron is 50000ppm

That is correct

1 hour ago, bfrenock said:

My question: Does anyone use a calibration liquid for iron similar to pH calibration liquids to verify a tester?

Yes that would be the way to calibrate your instrument  see link here http://hannainst.com/hi721-11-iron-checker-calibration-set.html

Sorry I can't help you with the calculations   metrics  is my language

cheers

Cecil likes this

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Thanks for the verification and the calibration set link.  Not sure why I didn't come across that when I did a quick search.  But I was more concerned that my calcs might be faulty :) .  Have a great day!

Bob

 

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I received the Hanna iron test kit yesterday and used it a few minutes ago.  My Checker read between 0.94ppm and 1.04ppm over five repeats of the test all within five minutes of adding the reagent to the iron test vial.  I then changed the battery in the Checker and repeated three more times with the same result.  My conclusion is that it is very likely that my Checker accurately measures iron within a few percent of the actual value.

Yesterday I also repeated the same test I mentioned above, adding an ounce (29.5 ml) of the 5% iron concentrate to three gallons (11.3 liters) of spring water.  The result was slightly different, reading just over 3ppm for the same solution that I thought should read 130ppm.

I also used an online concentration calculator to estimate the amount of 5% iron that would be needed to bring 3400 gallons (12870 liters) of water up to 1ppm (my approximate system volume).  Basically Volume1 x Concentration1 = Volume2 x Concentration2.  It came up with about 9 ounces (260 ml).  Over the past three weeks, I've added over 44 ounces (1300 ml) of the 5% iron and the highest concentration I recorded is 0.21ppm. On the bright side, The chlorosis I was experiencing in most of my crops seems to have improved quite a bit.

Although the containers of Biomin iron I've bought all appear to be originals, is it possible I'm getting a diluted knock-off?  Not being a chemist, I have no idea if anything in my spring water could be reacting with the iron when it is added to make the iron much less available to the iron reagent used to color the water.  One further test I'll try is using distilled water with the 5% iron solution to eliminate that possibility (once I get back into town to buy a container of distilled water).  I'll post that result once completed.

Any confirmations or critiques of my calculations or conclusions so far would be appreciated.

Thank you for your time.  Have a great day!

Bob

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I have perused the BrightAgrotech page a few times before, but thanks.  I notice they still don't have a recommendation for and organic iron supplement there.

I got my tissue and water sample results back from the lab finally.  The iron was below detectable limits (<0.05ppm).  But so were K, B, Mn, Zn and Cu.  Has anyone who has a mature pure aquaponics system done a water sample at a lab that would be willing to share their results?  Any comments on the other low values (since all nutes, w the exception of Fe and maybe K, are supposed to come from the fish)?

Thank you for your time.  Have a great day!

 

Bob

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Hi again

You could try contacting TCLynx http://aquaponicsnation.com/forums/profile/845-tclynx/

she haven't been on here fore some years so it might be easyer to contact her dierectly on her web site http://www.aquaponiclynx.com/?s=chelated+iron she runs a commercial "organic" AP operation in Florida. She use  and sells the product in Q, and she is usually very helpfull IME

 

cheers

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