# Salts Solubility levels!



## GHNelson

Below are individual Salt Solubility's in water at 20 degrees.
These levels could be less if mixed with other salts or if you mix with cold tap water!

Potassium Nitrate.......................................31g per 100ml
Potassium Phosphate................................ 22g per 100ml
Potassium Sulphate................................ 11.1g per 100ml
Magnesium Sulphate heptahydrate.......... 35.1 per 100ml
Calcium Sulphate dehydrate....................0.24g per 100ml
Calcium Chloride anhydrous.......................74g per 100ml

Magnesium nitrate.....................................125g per 100ml
Calcium nitrate...........................................121g per 100ml
Urea.............................................................107g per 100ml


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## drjack

Hi, I have a quick question. Before I read the solubility above for Potassium Sulphate I tried based on the calculator to dissolve *100.28 grams (equivalent to 5 tbsp + 0 tsp + 1/2 tsp + 1/8 tsp + 1/32 tsp )* of K2SO4 to your 500mL dosing container. As you will have guessed I now have a lot of undissolved K2SO4 in my 500ml container. I am unsure what I should do with it? Can I use it and what should I do with the undissolved K2SO4 at the bottom of the container? 
I am not a chemist, but in the future, if I were to dissolve 55.5g (not 100.28g) , as per above, in 500ml of water that is approx 55% of the calculator's instructions. Therefore, can I assume that I will now get 55% of 10ppm/degree of K i.e. 5.5 ppm/degree?

Many Thanks, David


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## Sammy Islam

I've always got something that doesn't fully dissolve in my macros even though i uae big diluted doses. I've tried changing salt supplier which didn't help. Just about to try different DI water and see if it makes any difference.


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## dw1305

Hi all,


drjack said:


> Hi, I have a quick question. Before I read the solubility above for Potassium Sulphate I tried based on the calculator to dissolve *100.28 grams (equivalent to 5 tbsp + 0 tsp + 1/2 tsp + 1/8 tsp + 1/32 tsp )* of K2SO4 to your 500mL dosing container. As you will have guessed I now have a lot of undissolved K2SO4 in my 500ml container........


You could try <"warming it up and stirring">, you normally have to do that to get anywhere near the solubility limit. 


drjack said:


> I am not a chemist, but in the future, if I were to dissolve 55.5g (not 100.28g) , as per above, in 500ml of water that is approx 55% of the calculator's instructions. Therefore, can I assume that I will now get 55% of 10ppm/degree of K i.e. 5.5 ppm/degree?


Yes.

cheers Darrel


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## drjack

Hi Darrel, thanks for the advice, much appreciated David


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## Hanuman

dw1305 said:


> You could try <"warming it up and stirring">, you normally have to do that to get anywhere near the solubility limit.


Only issue with that is, when back to ambient temperatures some will inevitably re-crystalize specially if doing the ferts during your winter times. No?


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## Hanuman

Sammy Islam said:


> I've always got something that doesn't fully dissolve in my macros even though i uae big diluted doses. I've tried changing salt supplier which didn't help. Just about to try different DI water and see if it makes any difference.


Could it be that perhaps it has not to do with the individual solubility levels but more with some elements reacting between each other?

This said when working on the IFC Calculator I noticed that data on solubility levels of some compounds could vary greatly from one data source to the other.


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## dw1305

Hi all,


Hanuman said:


> some will inevitably re-crystalize specially if doing the ferts during your winter times


Yes, you would need to re-heat the solution every time before you used it, to ensure that all the salts were in solution. You would also need to ensure that you made good any evaporation with RO water.


Hanuman said:


> Could it be that perhaps it has not to do with the individual solubility levels but more with some elements reacting between each other?


Yes, that is another issue. It is the <"Common Ion Effect">.  Have a look at the <"sequence of evaporite minerals"> derived from sea-water.

Personally I don't like working with <"small weights, small volumes or very concentrated solutions">. Theoretically it might seem fine, but in practice you are likely to run into problems.

cheers Darrel


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## Zeus.

dw1305 said:


> Personally I don't like working with <"small weights, small volumes or very concentrated solutions">. Theoretically it might seem fine, but in practice you are likely to run into problems.



Me too, no room for error, staying well away form solubility limits and just dose a larger volume as its an _pseudo_ auto top up, I do  serial dilutions for all trace elements (except Fe) when making DIY trace ferts, it just feels right when the weight of salt being added is between 5-15grams


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## dw1305

Hi all,


Zeus. said:


> Me too, no room for error, staying well away form solubility limits and just dose a larger volume as its an _pseudo_ auto top up, I do serial dilutions for all trace elements (except Fe) when making DIY trace ferts, it just feels right when the weight of salt being added is between 5-15grams


It just makes sense. I'm not saying that you can't be successful with Jeweler's scales etc. but I'm <"pretty slapdash"> and know where my limitations are.

cheers Darrel


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## Sammy Islam

Hanuman said:


> Could it be that perhaps it has not to do with the individual solubility levels but more with some elements reacting between each other?
> 
> This said when working on the IFC Calculator I noticed that data on solubility levels of some compounds could vary greatly from one data source to the other.





dw1305 said:


> Hi all,
> 
> Yes, you would need to re-heat the solution every time before you used it, to ensure that all the salts were in solution. You would also need to ensure that you made good any evaporation with RO water.
> 
> Yes, that is another issue. It is the <"Common Ion Effect">.  Have a look at the <"sequence of evaporite minerals"> derived from sea-water.
> 
> Personally I don't like working with <"small weights, small volumes or very concentrated solutions">. Theoretically it might seem fine, but in practice you are likely to run into problems.
> 
> cheers Darrel



Even though i use large dilute doses i think it was more of a reaction than a dissolving problem. I made up a new macro solution with K2SO4 and KH2PO4 and left out the KNO3, it seems to have dissolved properly.


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## Zeus.

Sammy Islam said:


> K2SO4



Can be tricky salt, half the dose in fert solution and toss dry salts in tank after WC to yield same weekly [K] dose. 
I take it your using RO water for fert solution ?


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## Sammy Islam

Zeus. said:


> Can be tricky salt, half the dose in fert solution and toss dry salts in tank after WC to yield same weekly [K] dose.
> I take it your using RO water for fert solution ?



Yes i am using DI water, I haven't tried that on this tank but i will do if i run into any NO3 problems.


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