soma
Hazard to Others
Posts: 297
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
solubility of magnesium hydroxide
I recently ran a reaction between MgSO4 and NaOH in water. The Mg(OH)2 is hard to filter out. I'm wondering if there's a better solvent to use that
would be easier to filter?
|
|
|
Fulmen
International Hazard
Posts: 1725
Registered: 24-9-2005
Member Is Offline
Mood: Bored
|
|
Magnesium hydroxide is pretty much insoluble in water (appr. 5ppm IIRC). Your problem is that the precipitate is extremely fine, this will make it
quite hard to filter. Industrially a flocculant is used to concentrate the ppt before filtering, but the result is a clay-like mass that is still high
in water.
I don't have any easy solutions other than letting gravity and time work for you.
We're not banging rocks together here. We know how to put a man back together.
|
|
|
walruslover69
Hazard to Others
Posts: 234
Registered: 21-12-2017
Member Is Offline
Mood: No Mood
|
|
How much Mg(OH)2 are you dealing with?
|
|
|
clearly_not_atara
International Hazard
Posts: 2799
Registered: 3-11-2013
Member Is Offline
Mood: Big
|
|
Magnesium forms hydroxy-sulfate crystals (also hydroxychloride) which have been used as a cement. To prevent this maybe start with magnesium acetate
or nitrate which I don't think will form these intermediate phases.
http://en.wikipedia.org/wiki/Sorel_cement
|
|
|
sclarenonz
Hazard to Self
Posts: 74
Registered: 13-12-2015
Location: BRASIL,oiapoque ,amapa
Member Is Offline
Mood: only the mission forget past
|
|
Good morning, I'm trying to isolate the magnesium, I noticed that when I added the hydrochloric acid in the magnesium carbonate solution, I got a
brown powder that I believe is the magnesium hydroxide, yours is a brown powder ?, I tried the electrolysis more unable to isolate, what is your goal
with dry magnesium hydroxide foot?
|
|
|
Iodobenzene
Harmless
Posts: 24
Registered: 27-12-2017
Location: In solution
Member Is Offline
Mood: Strongly Acidic
|
|
Despite it's very difficult to filter Mg(OH)2 ,i actually did it.
You must use 3 filters and before filtering the solution decant it. (Remove the more water you can)
Don't use vacuum.
Anyway Sclarenoz by mixing magnesium carbonate and HCl you get magnesium chloride,which is white.
So in your MgCO3 there were impurities.
[Edited on 29-12-2017 by Iodobenzene]
|
|
|
soma
Hazard to Others
Posts: 297
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
226.35 gms MgSO4 x 7(H2O) + 73.45 2(NaOH) -> 53.56 Mg(OH)2
[Edited on 30-12-2017 by soma]
|
|
|
ninhydric1
Hazard to Others
Posts: 345
Registered: 21-4-2017
Location: Western US
Member Is Offline
Mood: Bleached
|
|
In this case, I would let the fine particulate settle, than perform multiple decantations. Once you've removed enough filtrate you can filter as much
of the precipitate as possible. If it slips through the filter, just use decantation and wash with distilled water. Boil off the distilled water when
you believe you have removed most of the soluble byproducts. It seems like magnesium hydroxide is similar to calcium hydroxide in that it can form
fine particulate.
EDIT 1: fixed spelling errors.
[Edited on 12-30-2017 by ninhydric1]
The philosophy of one century is the common sense of the next.
|
|
|
soma
Hazard to Others
Posts: 297
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by sclarenonz  | | Good morning, I'm trying to isolate the magnesium, I noticed that when I added the hydrochloric acid in the magnesium carbonate solution, I got a
brown powder that I believe is the magnesium hydroxide, yours is a brown powder ?, I tried the electrolysis more unable to isolate, what is your goal
with dry magnesium hydroxide foot? |
I got hard white lumps after filtering and drying.
|
|
|
walruslover69
Hazard to Others
Posts: 234
Registered: 21-12-2017
Member Is Offline
Mood: No Mood
|
|
unless you are going for analytical results. I would recommend using coffee filters to separate the majority of the Mg(OH)2 I tried that once and I
was able to filter about 25-35g of Mg(OH)2 per coffee filter before it got clogged up. After you have filtered it, bake it in the oven until dry.
|
|
|
soma
Hazard to Others
Posts: 297
Registered: 31-7-2010
Member Is Offline
Mood: No Mood
|
|
I used a sintered funnel and vacuum. I filtered about 1/4 of the whole thing in a couple hours. It came out drop by drop.
|
|
|
Fulmen
International Hazard
Posts: 1725
Registered: 24-9-2005
Member Is Offline
Mood: Bored
|
|
sclarenonz: Magnesium hydroxide is white. And the reaction between magnesium carbonate and hydrochloric acid will produce water soluble magnesium
chloride, not an insoluble ppt. So whatever it is, it's not a magnesium compound.
We're not banging rocks together here. We know how to put a man back together.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
