[PASouza]

Hello all,

I'm new on this forum, so forgive me if I'm posting it in wrong section. Also, I'm from Brazil, sorry for my bad english.

I need the magnesium sulfate heptahydrate solubility curve, to make some mass balances. Can someone post it please? I will be grateful.

[Nobby]

Maybe this helps:

http://en.wikipedia.org/wiki/Solubility_table#M

[PASouza]

Hi, thanks for your feedback, but I need heptaydrate and not anhydrous, I will crystallize this salt, so I need his solubility from 0°C to 100°C or more

[Hunter2]

Hello, if you know the soloubilty of the anhydrous salt then you can calculate it also for the aqueous salt.

[magician4]

Hello, if you know the soloubilty of the anhydrous salt then you can calculate it also for the aqueous salt.

this would be true, if the anhydrous salt was the form that would crystallize from oversaturated solutions in all cases.
unfortunately, there are examples where this is not the case (for example with sulfates like Na₂SO₄ or K₂SO₄, respectively: those would crystallize as polyhydrates (below 30°C in case of Na₂SO₄ , that is, and with decreasing solubility at increasing temperature from there on )

So, if the original poster was interested in the precipitation of a well-definded hydrate, at least he would need to know the temperature range at which this type of hydrate will occur from oversaturated solutions, additionally

regards

Ingo

[PASouza]

Hello, if you know the soloubilty of the anhydrous salt then you can calculate it also for the aqueous salt.

And how I can make it? Thanks

[PASouza]

Hello, if you know the soloubilty of the anhydrous salt then you can calculate it also for the aqueous salt.

this would be true, if the anhydrous salt was the form that would crystallize from oversaturated solutions in all cases.
unfortunately, there are examples where this is not the case (for example with sulfates like Na₂SO₄ or K₂SO₄, respectively: those would crystallize as polyhydrates (below 30°C in case of Na₂SO₄ , that is, and with decreasing solubility at increasing temperature from there on )

So, if the original poster was interested in the precipitation of a well-definded hydrate, at least he would need to know the temperature range at which this type of hydrate will occur from oversaturated solutions, additionally

regards

Ingo

Let me explain.. I need to know which temperature MgSO4 has higher solubility, heat until this temperature and then cool down.

PS: Sorry for double-post

[Borek]

Let me explain.. I need to know which temperature MgSO4 has higher solubility, heat until this temperature and then cool down.

It doesn't guarantee you will get a heptahydrate, it can produce a hexahydrate as well.

Generally speaking magnesium sulfate solubility grows with temperature. Only slightly, but it grows.

Have you tried something like CRC handbook or something?

[PASouza]

Let me explain.. I need to know which temperature MgSO4 has higher solubility, heat until this temperature and then cool down.

It doesn't guarantee you will get a heptahydrate, it can produce a hexahydrate as well.

Generally speaking magnesium sulfate solubility grows with temperature. Only slightly, but it grows.

Have you tried something like CRC handbook or something?

No, I didn't.. but I need a concrete value to make my mass balances, I have an old paper who says "Epson Salt has higher solubility at 107ºC" but I need to make sure.

[Borek]

So go to the library and check the book.

[curiouscat]

Hello, if you know the soloubilty of the anhydrous salt then you can calculate it also for the aqueous salt.

this would be true, if the anhydrous salt was the form that would crystallize from oversaturated solutions in all cases.
unfortunately, there are examples where this is not the case (for example with sulfates like Na₂SO₄ or K₂SO₄, respectively: those would crystallize as polyhydrates (below 30°C in case of Na₂SO₄ , that is, and with decreasing solubility at increasing temperature from there on )

So, if the original poster was interested in the precipitation of a well-definded hydrate, at least he would need to know the temperature range at which this type of hydrate will occur from oversaturated solutions, additionally

regards

Ingo

Does the most hydrated form crystallize out in most cases? That'd be my naive hunch.

[Hunter2]

@ PAsouza

if you have the table of the anhydrous salt, then you can calculate

m_Anhyd/M_Anhyd = m_hepta/M_hepta

in case of magnesium sulfate if you want to dissolve 20 g Anhydrous salt

20g/120,36 g/mol = x g/246,47 g/mol

x = 40,96 g

In my opinion it doesn't matter what is real crystallization behavior as magican4 mentioned. Important is to get a saturated solution. In case of it will crystallize Hexa-hydrate or something else, then the whole experiment makes no sense.

[PASouza]

@ PAsouza

if you have the table of the anhydrous salt, then you can calculate

m_Anhyd/M_Anhyd = m_hepta/M_hepta

in case of magnesium sulfate if you want to dissolve 20 g Anhydrous salt

20g/120,36 g/mol = x g/246,47 g/mol

x = 40,96 g

In my opinion it doesn't matter what is real crystallization behavior as magican4 mentioned. Important is to get a saturated solution. In case of it will crystallize Hexa-hydrate or something else, then the whole experiment makes no sense.

Can this formula be used in any temperature? If I know anhydrous solubility at 100ºC, can I discover heptahydrate solubility at the sabe temperature?

[Hunter2]

Yes, I think so.

[PASouza]

Ok, thanks for help..