[NickBlack]

I'm broke, but I have a crummy lab in my basement, and some chemicals. I want to make a sodium Ion battery for funsies.
so I've decided I need some sodium iron phosphate, which I'll be making from sodium phosphate.. which means I need phosphoric acid.

I don't have phosphoric acid. I do have a few dozens of liters of urine stored up for extracting white phosphorous.. but I gotta wait till my GF id out of the house for a while before I work on that...

then I stumbled on an old box of miracle gro powder.. that contains phosphorous.. can I get at it? the box says it uses P2O5.. that's P4O10.. which should just turn straight into phosphoric acid when in water! to bad it comes with a lot of other junk.. and badly labled junk at that, so here's my work on figuring out what is (likely) in the box:

-----------------------------------------
as labeled on the container:

Guaranteed minimum analysis:
Total Nitrogen [N]------------------24%
Available Phosphate[P2O5]----------8%
Soluble Potash[K2O]----------------16%
Sulphur[S ]-------------------------4.0%
Boron[B ][Actual]-------------------0.02%
Copper[Cu][Actual]-----------------0.07%
Iron[Fe][Chelated][Actual]----------0.15%
Manganese[Mn][Chelated][Actual]---0.05%
Molybdenum[Mo][Actual]------------0.0005%
Zinc[Zn][Actual]--------------------0.06%
EDTA[Chelating Agent]--------------1.2%

personal note: EDTA (Ethylenediaminetetraacetic acid) primarily Chelates Iron & calcium
so that's probably how the Iron is Chelated

there is Ethylenediaminetetraacetic acid manganese disodium salt hydrate, which may be the way
the Manganese is Chelated..


-------------------------------------------------------------------
What the MSDS sheet says:
https://health.ho-chunk.com/sdsdocs/100336.pdf

Components-----------------------------CAS-No---------Weight %
di-Sodium-EDTA-------------------------139-33-3       <0.1
Potassium Phosphate--------------------7778-77-0       10-30
Boric acid, H3BO3-----------------------10043-35-3    0.1-1.0
Sodium molybdate, Na2MoO4+2H2O -----7631-95-0       <0.1
Iron EDTA ------------------------------15708-41-5    1.0-5.0
Manganese EDTA------------------------15375-84-5    0.1-1.0
Potassium chloride, KCl-------------------7447-40-7    10-30
Copper sulphate, CuSO4------------------7758-98-7    0.1-1.0
Zinc Sulfate-----------------------------7733-02-0    0.1-1.0
Ammoniumsulphate, (NH4)2SO4-----------7783-20-2    10-30
Urea -----------------------------------57-13-6       30-60


------------------------------------------------------------------------------------------------
off the walmart website (similar product):
https://www.walmart.com/ip/Miracle-Gro-Water-Soluble-All-Purpose-Plant-Food-1-5-lbs-Safe-for-All-Plants/16828998

Guaranteed Analysis:
Total Nitrogen (N) (24%),
Ammoniacal Nitrogen (3.5%), Urea Nitrogen (20.5%),
Available Phosphate (P2O5) (8%),
Soluble Potash (K2O) (16%),
Boron (B) (0.02%),
Copper (Cu) (0.07%),
Water Soluble Copper (Cu) (0.07%),
Iron (Fe) (0.15%),
Chelated Iron (Fe) (0.15%),
Manganese (Mn) (0.05%),
Chelated Manganese (Mn) (0.05%),
Molybdenum (Mo) (0.0005%),
Zinc (Zn) (0.06%),
Water Soluble Zinc (Zn) (0.06%).
Derived from Ammonium Sulfate,
Potassium Phosphate,
Potassium Chloride,
Urea,
Urea Phosphate,
Boric Acid,
Copper Sulfate,
Iron EDTA,
Manganese EDTA,
Sodium Molybdate,
Zinc Sulfate.

-----------------------------------------------------------------------------------

using that info, I'm guessing it has an ingredients list that looks closer to:

Ammoniacal Nitrogen[NH3-N]--------------(3.5%)
Urea Nitrogen[CO(NH2)2-N*]--------------(20.5%)
Potassium Phosphate [H2KO4P]------------(10%+) (note to self, has some cool electrical properties)
   this contains ([P2O5] ~50%+ & [K2O] ~35%+)
Potassium Chloride[KCl]-------------------?%
Urea Phosphate[CH7N2O5P]---------------?%**
Ammonium Sulfate(NH4)2SO4-------------10%+ ***
Copper sulphate[CuSO4]------------------0.1%+
Zinc Sulfate[ZnSO4]----------------------0.1%+
Boric acid[H3BO3]------------------------0.1%+
Copper Sulfate[CuSO4]-------------------0.1%+
Iron EDTA-------------------------------1%+
Manganese EDTA------------------------0.1%+
Sodium molybdate, [Na2MoO4+2H2O]-----0.1%-
Zinc Sulfate [ZnSO4]------------------- 0.1%+

*I'm guessing this is just plain old Urea, not sure why they call it Urea Nitrogen here, since that term seems to be specifically used in urea in the blood)
** dissisociates into Phosphoric acid & Urea in water.
*** this also contains quite a bit of nitrogen.. but isn't listed under 'N' because of a contradiction between the MSDS and the labels..

---------------------------------------------------------------------------

Possible procedure:

unfortunately distillation seems to be out (if anyone thinks different, please let me know, I'm by no means an expert)

so I'm thinking precipitation + electrolysis:

for some reason I can't seem to find if Potassium Phosphate actually dissasociates into P2O5 & K2O or not..
   assuming it does.. P2O5 (P4O10) should turn into phosphoric acid (H3PO4) when exposed to water
   (P4O10 + 6 H2O → 4 H3PO4   (–177 kJ))
   
assuming that is all the case, the procedure should be reasonably simple:
   dissolve as much miracle gro as you can into 100ml of (20'c) water.
   add sodium hydroxide.
      since NaHO & PO4- are both MUCH more soluble in water than things like Tri/sodium phosphate
   a few different sodium phosphate salts should precipitate out.
      - keep adding NaHO until nothing else precipitates out.
   filter off the solids. ('hopefully this should primarily be sodium phosphate salts, but will likely have some sodium carbonate and such as well.. good enough for me anyway... hopefully)
   dissolve those solids back into distilled water.
   do an electrolysis in a membrane separated cell to form the Tri/sodium phosphate back into NaOH & Phosphoric acid.

can anyone see any flaws? have any suggestions? Cheers!

[Hunter2]

You are on the wrong path. The label shows a mixture for a Phosphate fertilizer. Its not P2O5. Its only for calculation written, like the other compounds like K2O as well.

[NickBlack]

You are on the wrong path. The label shows a mixture for a Phosphate fertilizer. Its not P2O5. Its only for calculation written, like the other compounds like K2O as well.

if I understood you correctly, yes, there isn't any P2O5 in it's plain form in the box (despite the label saying it does) it's in a matrix with the K2O called "Potassium Phosphate" (more specifically Monopotassium phosphate, usually just called MKP)

I found it difficult to find straight answers, hence why I'm posting here rather than a vague "Fertilizer-grade MKP powder contains the equivalent of 52% P2O5 and 34% K2O" that other websites offer.

but since the liquid version of the same brand fertilizer is labeled as containing phosphoric acid, I found the idea that it does disassociate in water to form phosphoric acid to be a reasonable guesstimate.



What path would you suggest I look down?

[Hunter2]

Correct, its at least a pottasiumphosphate.. In water you get pottasium ions and phosphate ions, but no phosphoric acid and pottasium hydroxide. Its the same like sodium chloride in water will not form hydrochloric acid and sodiumhydroxide.

[NickBlack]

Correct, its at least a pottasiumphosphate.. In water you get pottasium ions and phosphate ions, but no phosphoric acid and pottasium hydroxide. Its the same like sodium chloride in water will not form hydrochloric acid and sodiumhydroxide.

i mean, yes, that's how salts dissolve. I guess it's inappropriate to call a solution with H+ protons and phosphate- ions if those aren't the only ions, and it's no longer acidic, phosphoric acid? (I'm self taught, so that's a genuine question)

since sodium ions are very greedy (reactive), adding sodium hydroxide, (Na+ protons and OH- ions) it should still produce sodium phosphate salts shouldn't it? (since once they form, they should drop out of solution, no longer being dissolved) shouldn't it?

[Borek]

I guess it's inappropriate to call a solution with H+ protons and phosphate- ions if those aren't the only ions, and it's no longer acidic, phosphoric acid?

Yes, no chemist would call it that.

since sodium ions are very greedy (reactive)

Quite the opposite, they are mostly inert and it is very difficult to make them react with anything.

adding sodium hydroxide, (Na+ protons and OH- ions) it should still produce sodium phosphate salts shouldn't it? (since once they form, they should drop out of solution, no longer being dissolved) shouldn't it?

Whether the salt crashes out from the solution depends on its solubility. Sodium salts tend to be well soluble, so they will stay dissolve quite long.

But I believe there is something else that you are missing. Imagine you prepare a solution by adding 1 mole of NaCl and 1 mole of KBr to 1L of water. Both salts dissolve and dissociate. You have a solution containing 1 mole of Na⁺, 1 mole of K⁺, 1 mole of Cl^- and 1 mole of Br^-. Is it different from solution prepared by dissolving 1 mole of NaBr and and 1 mole of KCl? Does it still make sense to speak any of these four salts being present?

Your solution contains - between other things - PO₄^3- (actually mostly HPO₄^2- and H₂2PO₄^-, which is another thing that complicates the situation), some H⁺ (every water solution does), some K⁺, some Na⁺ - does it make sense to speak about phosphoric acid, sodium phosphate and potassium phosphate?

[Sideshow]

If you want phosphoric acid - and to save yourself the hassle of trying to extract it from fertilizer (do-able but a PITA) - go and look for a phosphoric acid rust converter at the local hardware. Most of them are simply orthophosphoric acid, occasionally with a few other traces - dyes, maybe a co-solvent like MGBE, or a trace of chromium, but all in acid form and usually at 30 - 40% w/v H3PO4.

Simple enough to concentrate by distillation - bits and pieces can either be fractionally distilled off or removed by complexation or precipitation.

And, further to Borek's comments :

What you have in Miracle Gro is a complex fertilizer - fully soluble and with certain chelates present, as you've already noted.

Separation therefore becomes a problem of removing as many compounds as you can that aren't the material you're looking for ... so ... (and this process IS NOT for the faint-hearted)

Ammonia can be driven off by the addition of a strong base and boiling to reduce volume until there's no odour of ammonia.

You may get away with it using potassium carbonate, which has the added advantage of, potentially, forming insoluble carbonates for the transition metals that can be filtered off.

The resulting solution will then contain residual sodium and potassium salts of  phosphate,  chloride, free  carbonate,  molybdate and urea (you might have removed some of the urea via hydrolysis if your pH was high enough when you boiled the solution). Allow to cool.

Mix with calcium oxide or calcium hydroxide - this should form a mixture of calcium phosphate (insoluble) and calcium sulphate (insoluble) and maybe a little calcium chloride (soluble). Filter and retain the insolubles - rinse with DI water.

Collect the resulting precipitate and treat with concentrated sulphuric acid (98% qs) to convert calcium to calcium sulphate (insoluble) and free phosphoric acid. Filter and collect the crude Phos acid (H3PO4) - concentration and purification is left as an exercise for the student.

Or go to the first line of this post (recommended).