Sciencemadness Discussion Board - Is there anything useful here ?

Is there anything useful here ?

Sulaiman - 1-7-2015 at 16:24

I bought some fertiliser for my garden
and I'm wondering if there is any useful products that I can extract from it.
the contents

e.g. how difficult would it be to get elemental phosphorous

I would like to analyse the contents but I am way out of my depth
so I'm asking for a little spoon-feeding

The fertiliser is a mixture of three ingredients;
brick red granules
grey balls
translucent white/yellow balls

any (educated) guesses as to what is in each type?

blogfast25 - 1-7-2015 at 17:27

Leaching with boiling water and filtering will obviously yield a solution containing phosphate (mainly dihydrogen phosphate, I believe), ammonium, nitrate and potassium ions.

But separating these into useful products isn't easy, especially if you haven't any analytical tools to determine your progress with.

Reducing the solution down until the first crystals form, then chilling should separate out the least soluble K salt, which is probably KNO3.

See Wikipedia's solubility table for some guidance.

For phosphorus, consult the relevant sticky thread in General Chemistry.

[Edited on 2-7-2015 by blogfast25]

Bert - 1-7-2015 at 20:40

Look for a section of the label that starts with "derived from"...

violet sin - 1-7-2015 at 21:10

FYI- "labeling scheme do not directly represent the source composition or absolute nutrient content of the fertilizer. The N value is the percentage of elemental nitrogen by weight in the fertilizer. The values for P and K represent the amount of P2O5 and K2O that would be present if all the phosphorus and potassium in the fertilizer appeared in these forms.[3]"
Wiki: https://en.m.wikipedia.org/wiki/NPK

Some people don't know this, so if you did, no offence. There is never K₂O etc. In the bottle. There also may be chelator components for time release. Clay binders, wax fillers. Even if the source for all the K is from one product, more than likely part will dissolve, part will sink and part will be filled. The source used in fertilizers isn't that strict.

Like 0-0-50 I bought. Supposed to be only K₂SO₄, but Cl, SO₄, CO₃ etc. mix. With calcium sulfate in There too.

blogfast25 - 2-7-2015 at 04:44

Quote: Originally posted by violet sin

There is never K₂O etc. In the bottle. There also may be chelator components for time release. Clay binders, wax fillers. Even if the source for all the K is from one product, more than likely part will dissolve, part will sink and part will be filled. The source used in fertilizers isn't that strict.

Well, of course it doesn't contain any K2O or P2O5.

"20 % water soluble K2O" means that if you determine the actual K content on a water leachate, then express this as K2O, that value is about 20 % of the fertiliser. Same with the P2O5.

'On paper', using some reasonable assumptions, mass balances and neutrality balance the composition of an aqueous leachate could be estimated in terms of mol KNO3, mol NH4NO3 and mol NH4H2PO4, from the N-P-K value&.

As Bert suggested though, its intended use is also its easiest and most cost effective use!

Edit:

& According to that calculation an aqueous lixiviate obtained from 1 kg of fertilizer would contain about :

2 mol KNO3
3.5 mol NH4NO3
0.9 mol NH4H2PO4

For someone who has trouble sourcing KNO3 this might be worth the effort.

[Edited on 2-7-2015 by blogfast25]

Sulaiman - 2-7-2015 at 04:48

Although I read that NPK measurements are relative to P2O5, K2O etc.
It did not occur to me that my fertiliser does not (necessarily) contain actual P2O5 or K2O
so thanks for that info.

blogfast25 - 2-7-2015 at 05:37

Quote: Originally posted by Sulaiman

Although I read that NPK measurements are relative to P2O5, K2O etc.
It did not occur to me that my fertiliser does not (necessarily) contain actual P2O5 or K2O
so thanks for that info.

How could it? Both are extremely reactive materials!

This way of expressing content is old fashioned yet still widely used: I sell aluminium sulphate hydrate that is characterised by its Al2O3 content!