Chemgineer
Hazard to Others
Posts: 223
Registered: 25-5-2021
Member Is Offline
|
|
Sulfate of potash fertiliser.
I bought some sulfate of potash fertiliser with the intention of putifying it to potassium sulfate by dissolving in water, filtering and drying.
I was intrigued to see on the packet that the contents are actually:
Potassium oxide K2O 52%
Sulphur trioxide SO3 48%
Now I understand that on adding water the K20 will produce KOH and the SO3 will produce H2SO4 and thus neutralise each other producing K2SO4.
It would be nice though if the SO3 could instead be isolated and H2SO4 be produced on it's own. I don't expect this is possible though.
|
|
|
imidazole
Harmless
Posts: 28
Registered: 18-10-2014
Location: Massachusetts, USA
Member Is Online
Mood: Radical
|
|
I hate to say it, but those are just the "active components" listed for fertilizer stuff, In actuality it's most likely just K2SO4.
Fertilizer has an odd notation style where they list things as oxides, for instance it tries measuring phosphorus as P2O5, if I remember correctly.
|
|
|
fx-991ex
Hazard to Others
Posts: 108
Registered: 20-5-2023
Member Is Offline
|
|
instead of dissolving filter and drying why not recrystallize it?
like get a liter of water to boil add 240g till it dissolved completly, try filtering hot(if you see undissolved contams) and let cool down as much as
you can.
[Edited on 17-3-2025 by fx-991ex]
[Edited on 17-3-2025 by fx-991ex]
|
|
|
Chemgineer
Hazard to Others
Posts: 223
Registered: 25-5-2021
Member Is Offline
|
|
Quote: Originally posted by fx-991ex  | instead of dissolving filter and drying why not recrystallize it?
like get a liter of water to boil add 240g till it dissolved completly, try filtering hot(if you see undissolved contams) and let cool down as much as
you can.
[Edited on 17-3-2025 by fx-991ex]
[Edited on 17-3-2025 by fx-991ex] |
I would but the solubility doesn't change that much with temperature for potassium sulfate.
100 deg C 24g / 0 deg C 7.4g
|
|
|
fx-991ex
Hazard to Others
Posts: 108
Registered: 20-5-2023
Member Is Offline
|
|
| Quote: Originally posted by Chemgineer | | Quote: Originally posted by fx-991ex | instead of dissolving filter and drying why not recrystallize it?
like get a liter of water to boil add 240g till it dissolved completly, try filtering hot(if you see undissolved contams) and let cool down as much as
you can.
[Edited on 17-3-2025 by fx-991ex]
[Edited on 17-3-2025 by fx-991ex] |
I would but the solubility doesn't change that much with temperature for potassium sulfate.
100 deg C 24g / 0 deg C 7.4g |
thats enough, remove crystals then just re-heat it and evap water till it start precipitating and let it cool you will get another crop, you can do
that repeatedly till almost nothing is left(but contams).
Make sure you cool it till it almost freeze(salt water freeze below 0C so you can probably get it to -10 to -20C, if it freeze just let it warm up a
bit for ice to melt then filter.)
Like let it cool to room temp, then in the refrigerator then into freezer to avoid cooling too fast.
[Edited on 17-3-2025 by fx-991ex]
|
|
|
MrDoctor
Hazard to Self
Posts: 60
Registered: 5-7-2022
Member Is Offline
|
|
as its totally insoluble in acetone, it might be possible to add acetone to a saturated solution to precipitate it rapidly without having to boil it
down, although idk how miscible acetone would be in this saturated water.
Also, the solubility data for 40% ethanol is less than 1g/100ml
You have an abundance of relatively low purity, cheap material though, so slow, small crops of crystals with wide margins of loss might be desireable
depending on the application.
at the cost of time, it may be possible to apply the hydrothermal method of crystal growth used for copper sulfate here. it amounts to having a tall
container where a saturated solution with excess solid in the bottom is heated, and it precipitates on a nucleation point, usually a crystal, in the
middle between the hot and cold region. solids dissolve and recrystalize slowly, forming huge clean mono-crystals, but i think you can speed the
process up somehow to get faster formation. Depends how pure you want them, and when, id probably do this if i was going to make a catalyst of sorts
but didnt need it for a month.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
