1000national - 7-11-2007 at 12:27
Okay....newbie question for my high school daughter....
How do you fully dehydrate magnesium sulfate MgSO4?
And how do you know when it's fully dehydrated?
A step-by-step would be great......
Thanks guys...and gals,
Steve
pantone159 - 7-11-2007 at 12:38
I put the 7-hydrate ("Epsom salts") in the oven at around 450 F (sorry for the units), for around an hour. This leaves the remains hard and solid, so
I grind it up, and then reheat to drive off any available water that got held up by the solid mass. (It stays loose after the first time.)
However, I find that I only drive off about 6 water molecules, the result is thus probably MgSO4-H2O. It does seem to work fine as a drying agent,
though.
Nerro - 7-11-2007 at 13:03
That's because you're heating it to ~230°C and you need to heat it to 250°C to completely dehydrate it completely. I don't think it really matters
though. The monohydrate will also dehydrate solutions because it too will form the heptahydrate.
It will be dehydrated when the powder is really a powder and in no way clumping together.
So, you buy epsom salts and you heat the crystals in your oven at it's highest setting. Once you think it's drystore it in an airtight bottle to
prevent airborne water from reacting with it.
1000national - 7-11-2007 at 13:13
Thanks for the replies:
So heat it to 250C for X minutes
Grind into powder form...repeat heating?
and now it should be fully dehydrated?
I understand it's a powerful dessicant so prompt
measuring will be required.....
Anything else????
Thanks,
Steve
Eclectic - 7-11-2007 at 13:20
If you heat in stages it won't dissolve in it's own water of crystallization. 125-150C several hours with stirring occasionally, then 250 a few more,
then 300 to drive out the last bit of water if you like.
Dessicant from Epsom Salts
1000national - 7-11-2007 at 15:22
That's exactly what she needed to know....
This board rocks.......Thanks a bunch,
Steve
WizardX - 7-11-2007 at 16:13
Simply grind the MgSO4 • 7H2O = Magnesium Sulfate Heptahydrate (Epsom Salts) into a fine powder first, then spread it onto large baking trays for
maximum surface area.
Preheat oven to 250°C plus.
Heat to 250°C for 2 hours = 482°F Loses all waters of hydration. Yielding Anhydrous Magnesium Sulfate.
While heating, quickly stir around the hot powder to break-it-up and expel the water vapour in the oven. Approx every 30 min.
After 2 hours, remove the hot Anhydrous Magnesium Sulfate powder from the oven and place it on aluminium foil and seal it from air contact, and allow
to cool.
After cooled, place in air tight container.
12AX7 - 7-11-2007 at 16:48
Heating slowly, especially through the 150-200C area, allows the crystals to effloresce to powder cleanly. Going up to 250-300C likewise should get
rid of the last H2O just as nice. You don't want to heat at once because the crystals melt and fuse into a solid lump that dehydrates into a hard
lump that needs to be ground up.
Ain't that always the way, slow cooked is the best.
Tim