Sciencemadness Discussion Board

Antimony (iii) oxide and hcl.

Chemgineer - 6-8-2024 at 12:46

I am confused, I have some antimony (iii) oxide and I expected that on mixing with hcl it would release oxygen, neutralise the acid and end up as a solution of antimony (iii) chloride.

Is this a slow reaction that needs time and heating or am I missing something?

I'm not seeing a fizzing like you would with a carbonate and i'm collecting white precipitate at the bottom of my beaker, Although I think less than the oxide i've added.

B(a)P - 6-8-2024 at 14:25

Quote: Originally posted by Chemgineer  
I am confused, I have some antimony (iii) oxide and I expected that on mixing with hcl it would release oxygen, neutralise the acid and end up as a solution of antimony (iii) chloride.

Is this a slow reaction that needs time and heating or am I missing something?

I'm not seeing a fizzing like you would with a carbonate and i'm collecting white precipitate at the bottom of my beaker, Although I think less than the oxide i've added.


There is some discussion in this thread.
https://www.sciencemadness.org/talk/viewthread.php?tid=9551

bnull - 6-8-2024 at 14:37

Quote:
I have some antimony (iii) oxide and I expected that on mixing with hcl it would release oxygen, neutralise the acid and end up as a solution of antimony (iii) chloride.

Is this a slow reaction that needs time and heating or am I missing something?

I'm not seeing a fizzing like you would with a carbonate

It doesn't release oxygen upon dissolution in acids. If it were to, then it would have to reduce its oxidation number from +3 to something else (say, +2). It is not a peroxide either, and again no oxygen release. The only product besides SbCl3 is water, hence no fizzing.

Quote:
and i'm collecting white precipitate at the bottom of my beaker, Although I think less than the oxide i've added.

It may be one of the oxychlorides. Your antimony trichloride may be hydrolising, although I wouldn't expect it to happen immediately. Are you using concentrated acid?

Edit: :P Ninja attack...

[Edited on 6-8-2024 by bnull]

Chemgineer - 6-8-2024 at 14:39

Quote: Originally posted by bnull  
Quote:
I have some antimony (iii) oxide and I expected that on mixing with hcl it would release oxygen, neutralise the acid and end up as a solution of antimony (iii) chloride.

Is this a slow reaction that needs time and heating or am I missing something?

I'm not seeing a fizzing like you would with a carbonate

It doesn't release oxygen upon dissolution in acids. If it were to, then it would have to reduce its oxidation number from +3 to something else (say, +2). It is not a peroxide either, and again no oxygen release. The only product besides SbCl3 is water, hence no fizzing.

Quote:
and i'm collecting white precipitate at the bottom of my beaker, Although I think less than the oxide i've added.

It may be one of the oxychlorides. Your antimony trichloride may be hydrolising, although I wouldn't expect it to happen immediately. Are you using concentrated acid?

Edit: :P Ninja attack...

[Edited on 6-8-2024 by bnull]


I am using 20% hcl.

[Edited on 6-8-2024 by Chemgineer]

Precipitates - 6-8-2024 at 18:35

May still not be enough. I'm sure I've had trouble (or at least noticed) oxychlorides or oxynitrates in the past (can't remember the compound though, maybe copper), in pretty strongly acidic solutions.

20% HCl is the starting concentration, but of course upon antimony (III) oxide addition this will rapidly reduce.

Antimony trichloride will convert to antimony oxychloride in the smallest amount of water.

In any case, after completely adding the antimony (III) oxide to a large excess of the acid, I'd try heating the solution to concentrate the remaining acid and hopefully dissolve the precipitate*. Once a clear solution has been obtained, the solution can be gently heated to dryness. Given how sensitive this compound is to moisture, it will need to be stored straight away in an air-tight container.

Sciencemadness wiki has a nice summary of probably the best routes to pure antimony (III) trichloride.

*May need to add even more acid.

woelen - 8-8-2024 at 13:15

Antinomy(III) oxide, Sb2O3, dissolves in excess concentrated hydrochloric acid quite easily, giving a clear and colorless solution. However, even moderately concentrated acid (e.g. 20%) already has quite some difficulty dissolving Sb2O3. With 10% HCl, only very dilute solutions can be obtained.

If you prepare a solution of Sb2O3 in conc. HCl (at least 30% by weight), then you can dissolve a few hundreds of mg (a nice heap of solid on the tip of a big screw driver) in 5 ml of acid or so. On addition of some water, the clear liquid becomes turbid and a white precipitate is formed. SbCl3 very very easily hydrolysed in water, to SbOCl and HCl, or even back to Sb2O3 (at high dilution, or at somewhat alkaline conditions).

[Edited on 8-8-24 by woelen]

chloric1 - 8-8-2024 at 16:22

Quote: Originally posted by woelen  
Antinomy(III) oxide, Sb2O3, dissolves in excess concentrated hydrochloric acid quite easily, giving a clear and colorless solution. However, even moderately concentrated acid (e.g. 20%) already has quite some difficulty dissolving Sb2O3. With 10% HCl, only very dilute solutions can be obtained.

If you prepare a solution of Sb2O3 in conc. HCl (at least 30% by weight), then you can dissolve a few hundreds of mg (a nice heap of solid on the tip of a big screw driver) in 5 ml of acid or so. On addition of some water, the clear liquid becomes turbid and a white precipitate is formed. SbCl3 very very easily hydrolysed in water, to SbOCl and HCl, or even back to Sb2O3 (at high dilution, or at somewhat alkaline conditions).

[Edited on 8-8-24 by woelen]



Wow thanks so comprehensive. I love getting lost in your chemistry website! About the only use I’d have for antimony would be part of a metal patina formula. I’m stocking up preparing some nitrates and acetates. Copper acetate has a REALLY low solubility BTW