Sciencemadness Discussion Board
Not logged in [Login - Register]
Go To Bottom

Printable Version  
Author: Subject: solubility of magnesium hydroxide
soma
National Hazard
****




Posts: 297
Registered: 31-7-2010
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 06:35
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?
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1226
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 29-12-2017 at 07:49


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.
View user's profile View All Posts By User
walruslover69
Hazard to Others
***




Posts: 167
Registered: 21-12-2017
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 08:13


How much Mg(OH)2 are you dealing with?
View user's profile View All Posts By User
clearly_not_atara
International Hazard
*****




Posts: 1563
Registered: 3-11-2013
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 10:04


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




[Edited on 04-20-1969 by clearly_not_atara]
View user's profile View All Posts By User
sclarenonz
Hazard to Self
**




Posts: 60
Registered: 13-12-2015
Location: BRASIL, BAHIA , CONCEICAO DO COITE
Member Is Offline

Mood: keep walking

[*] posted on 29-12-2017 at 11:12


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?
View user's profile Visit user's homepage View All Posts By User
Iodobenzene
Harmless
*




Posts: 24
Registered: 27-12-2017
Location: In solution
Member Is Offline

Mood: Strongly Acidic

[*] posted on 29-12-2017 at 15:18


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]
View user's profile View All Posts By User
soma
National Hazard
****




Posts: 297
Registered: 31-7-2010
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 19:51


Quote: Originally posted by walruslover69  
How much Mg(OH)2 are you dealing with?

226.35 gms MgSO4 x 7(H2O) + 73.45 2(NaOH) -> 53.56 Mg(OH)2

[Edited on 30-12-2017 by soma]
View user's profile View All Posts By User
ninhydric1
National Hazard
****




Posts: 340
Registered: 21-4-2017
Location: Western US
Member Is Offline

Mood: Bleached

[*] posted on 29-12-2017 at 19:55


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.
View user's profile View All Posts By User
soma
National Hazard
****




Posts: 297
Registered: 31-7-2010
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 19:56


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.
View user's profile View All Posts By User
walruslover69
Hazard to Others
***




Posts: 167
Registered: 21-12-2017
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 19:59


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.
View user's profile View All Posts By User
soma
National Hazard
****




Posts: 297
Registered: 31-7-2010
Member Is Offline

Mood: No Mood

[*] posted on 29-12-2017 at 20:05


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.
View user's profile View All Posts By User
Fulmen
International Hazard
*****




Posts: 1226
Registered: 24-9-2005
Member Is Offline

Mood: Bored

[*] posted on 30-12-2017 at 03:06


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.
View user's profile View All Posts By User

  Go To Top