Purity of fert powders - The Planted Tank Forum
 
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post #1 of 7 (permalink) Old 10-27-2014, 11:15 PM Thread Starter
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Purity of fert powders

I've ordered some KNO3 and KH2PO4 on [Ebay Link Removed] One has been delivered. I say one, because it is an unlabelled bag of powder....
I'm happy I can differentiate them based on wildly different pKa's if the other arrives unlabelled....

This is fertiliser grade stuff - is this considered pure enough? OK for our fish? Does anyone do any sort of purification steps?
Should I obtain from somewhere else??

I've just been through some heinous fish die offs I think I traced to toxins leaching from my garden hose, the last thing I want to do is put more rubbish in!

cheers
Lee
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post #2 of 7 (permalink) Old 10-28-2014, 12:03 AM
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Hi Lee,

As long as you can identify the substance with enough assurance, that it is KNO3 or KH2PO4, it should be okay.

At fertilizer grade, they do not have to be very pure.

Recrystallizing is an easy method, a time or two just to get rid of the junk (and see some of the junk), 17-27 times for high purity.

Anyway, if you need any help let me know I’ll be back in a couple of hours…

God willing and the creek don’t rise… Always kind of seemed the creek ought to be under God’s control… Maybe one of the religious leaders could help me out with this one.

Respectfully,
Joe
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post #3 of 7 (permalink) Old 10-28-2014, 03:24 AM Thread Starter
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Why I was considering pKa when I have a nitrate test kit....
On the assumption it was KNO3, I made a solution of 220ppm, and the nitrate test kit certainly showed a result >160ppm. A 1 in 10 dilution I read as between 20 and 40ppm.
I'm happy it is KNO3 - looks macroscopically clean/homogenous too...

Funny - the word "ebay" in my initial post has been replaced with [Ebay Link Removed] - not much difference really.....
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post #4 of 7 (permalink) Old 10-28-2014, 07:22 AM
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As eBay links are not permitted the filter is set up so that a period (.) after the word eBay will result in an automatic censor.

For our purposes, agricultural grade chemicals will be fine.

Anthony


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post #5 of 7 (permalink) Old 10-28-2014, 08:16 AM
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Hi Lee,

Sounds good, always better to check.

To be sure, it is Potassium nitrate burn a little see if you get a violet flame. A little more fun is equal parts (⅟2-teaspoon each) suspect KNO3 and sugar, outside in a safe place, butane fireplace torch, if it is KNO3 it will burn energetically with a Lilac, violet (pale purple, some variation of purple) flame.

The down-and-dirty test for Potassium (metals) is a wire (metal paperclip will do) cleaned with Hydrochloric acid (muriatic acid) dipped in suspected potassium compound and held in a flame (alcohol lamp or propane torch or butane fireplace lighter).
  1. Be careful,
    1. Hydrochloric acid (muriatic acid) can hurt you
    2. Fire can be hot and burn you and your surroundings
    3. The suspected (nitrate) compounds can be highly flammable

  1. Clean the wire (metal paperclip) by
    1. dipping in Hydrochloric acid (muriatic acid) and
    2. holding the wire in the flame
    3. repeat 2 or 3 times or until no change in the color of the flame

  1. Dip the wire (metal paperclip) in Hydrochloric acid (muriatic acid)
    1. Then in suspected potassium compound
    2. Then hold wire with suspected potassium compound in flame.

  1. If the flame is Lilac, violet (pale purple, some variation of purple)
    1. It is likely a potassium compound possibly KNO3

  1. If the flame is some variation of orange (toward the yellow end)
    1. It is a Sodium compound possibly NaNO3

  1. If the flame is some variation of red (brick red) (toward orange)
    1. It is a calcium compound possibly Ca(NO3)2

  1. If the flame is some variation of blue
    1. It is a magnesium compound, possibly Mg(NO3)2

  1. No color
    1. It may be NH4NO3

Respectfully,
Joe
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post #6 of 7 (permalink) Old 10-28-2014, 09:21 AM Thread Starter
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Thanks Joe - I was thinking of ways to ensure it was the K salt - I had thought of the sugar rocket experiment (I'm also into amateur rocketry). but not of the flame photometry - cheers.
I should have thought to look that stuff up, 20 years ago I was very good at chemistry, and even finished 2/3 of a chem major science degree, before changing directions in biological sciences.....
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post #7 of 7 (permalink) Old 10-28-2014, 11:00 AM Thread Starter
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Mmmm - definitely more a yellow flame noted with the wire loop. Certainly burnt well with ground sugar, I think I could see a hint of purple then. I think I'll recrystallize it...
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