Lancer85
Harmless
Posts: 13
Registered: 13-6-2024
Member Is Offline
|
|
Removing sulfuric acid from a solid
I have a solid that I can separate from 40% sulfuric acid by cooling to -23c in the freezer. After filtering on a buchner, it remains wet with the
sulfuric acid residue. I have tried washing the solid with 1c temperature distilled water but too much of the solid dissolves in the water. I tried
extracting with ethyl acetate but the sulfuric acid degrades too much of the ethyl acetate into acetic acid and then the acetic acid then reacts with
my product. Maybe a 20% CaCl2 solution at -23c and wash the solid will pull the sulfuric acid off the solid and leave only a minor CaCl2 contamination
upon drying?
What could I do in this situation?
|
|
|
bnull
National Hazard
Posts: 635
Registered: 15-1-2024
Location: The country that made an art of fence-sitting
Member Is Online
Mood: I'm back, sort of.
|
|
What substance is the solid?
|
|
|
BromicAcid
International Hazard
Posts: 3277
Registered: 13-7-2003
Location: Wisconsin
Member Is Offline
Mood: Rock n' Roll
|
|
Depending on the volatility of your solid you could just dry it under full vacuum. Sulfuric would come off at 0.1 mm Hg and 100°C.
You could also try washing with cold MeOH or EtOH. I'm not too familiar with the risk of forming esters under these conditions but I think it's
pretty much nill as long as you're keeping at room temperature or cooler.
[Edited on 4/8/2025 by BromicAcid]
|
|
|
Sulaiman
International Hazard
Posts: 3794
Registered: 8-2-2015
Member Is Offline
|
|
As 40% sulphuric acid does not dehydrate materials like 98% does,
I guess that filter paper material would absorb the acid without disintegrating or contaminating your product.
Repeated pressings between fresh papers may work?
I guess that finer papers would produce less product loss.
CAUTION : Hobby Chemist, not Professional or even Amateur
|
|
|
Lancer85
Harmless
Posts: 13
Registered: 13-6-2024
Member Is Offline
|
|
The product is protocatechualdehyde. It is soluble in solvents such as ethanol and methanol. It is also very heat sensitive.
|
|
|
Precipitates
Hazard to Others
Posts: 166
Registered: 4-12-2023
Location: SE Asia
Member Is Offline
Mood: Acid hungry
|
|
Quote: Originally posted by Lancer85  | | Maybe a 20% CaCl2 solution at -23c and wash the solid will pull the sulfuric acid off the solid and leave only a minor CaCl2 contamination upon
drying? |
Can try it - and then crystallise from ethyl acetate if concerned about calcium chloride or sulphate impurities.
|
|
|
Texium
Administrator
Posts: 4685
Registered: 11-1-2014
Location: Salt Lake City
Member Is Offline
Mood: Preparing to defend myself (academically)
|
|
| Quote: Originally posted by Lancer85 | | The product is protocatechualdehyde. It is soluble in solvents such as ethanol and methanol. It is also very heat sensitive. |
That stuff is a real pain to work with. Recrystallizing it just makes it less pure. You’re better off not isolating it and just
carrying it crude into whatever your next step is, if you can.
The CaCl2 idea is questionable. You’ll have CaSO4 precipitate mixed with your product.
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
