# Potassium bonded with...?



## Geoffrey Rea (7 Feb 2020)

K2SO4?


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## dw1305 (7 Feb 2020)

Hi all, 





Geoffrey Rea said:


> K2SO4?


I can't really tell from the image, but do you have a swirl of precipitated compound? It probably isn't your K+, or SO4-- ions, that have come out of solution, because all <"potassium, and nearly all sulphate, salts  are soluble">. 

If it is a very concentrated solution? you <"may have exceeded the solubility limit">, which 120g/L for K2SO4 at 25oC. If it is an "all-in-one" solution the least soluble ions will come out of solution first via the <"common ion effect">.

cheers Darrel


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## Witcher (7 Feb 2020)

I was (un)lucky enough to have garden grade salts quite often contaminated with unknown ingredients, so switched to lab grade - this may be the case with your K2SO4 as well.


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## Geoffrey Rea (7 Feb 2020)

This isn’t a problem I have, just curious.

Sorry @dw1305 just realised what swirl you were referring to. That’s the pump on the bottle as I decanted it into a clear bottle and took the photo looking upwards. So not a swirl of precipitated compound no, it’s fully in solution.

It’s an over the counter product sold as a source of potassium for aquarium plants. No other details (as per usual) and would like to have a guess at what it is.

Poured out it’s golden in colour. First guess was K2SO4. Alternative is K2O due to its pale yellow colour in solution.

If it was K2O I assume it was produced by heating potassium peroxide:

2 K2O2 > 2 K2O + O2^


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## dw1305 (7 Feb 2020)

Hi all, 





Geoffrey Rea said:


> Poured out it’s golden in colour. First guess was K2SO4. Alternative is K2O due to its pale yellow colour in solution.


Potassium oxide (K2O) would be easy to check for via a pH measurement, it is a base. Potassium sulphate and potassium chloride (KCl) are neutral salts and won't change pH. All agricultural fertilisers have their K content expressed as potash (K2O), even though the compound doesn't contain any K2O. Potassium oxides are yellow compounds, but they are highly reactive and I'm pretty sure that isn't what you've bought. 





Geoffrey Rea said:


> It’s an over the counter product sold as a source of potassium for aquarium plants


The cheapest potassium salt  to buy is potassium chloride (KCl), there are actually <"mineable deposits"> of this (<"even in the UK">) where it is mixed with iron, and that would be my guess. 





Geoffrey Rea said:


> No other details (as per usual) and would like to have a guess at what it is.


I'd be interested in any more details, the UK potash source is a <"polyhalite" mine">, so it has a lot strange <"evaporite minerals"> present.

cheers Darrel


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## Geoffrey Rea (7 Feb 2020)

Only other claim from the manufacturer that I can find is it’s stable between a pH range of 3.5-8.5 @dw1305 

It was originally in a blacked out bottle which would make sense if it was KCl mixed with Fe.


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