Possible to desiccate Chromic acid?

[KOLM]

Hi,

Have some chromic acid and it is very damp as it is very hygroscopic. Does anyone know of a way to dry it out? Maybe over conc sulfuric acid or anhydrous calcium chloride? Could not find anything on the internet. 

Thanks.

[chenbeier]

For what reason you want to dry it. It's a very poisson and cancerogene stuff. Normally it will be dissolved in water or sulfuric acid as etching compound.

Drying  with Phosphorous pentoxide is possible.

 

[KOLM]

16 hours ago, chenbeier said:

For what reason you want to dry it. It's a very poisson and cancerogene stuff. Normally it will be dissolved in water or sulfuric acid as etching compound.

Drying  with Phosphorous pentoxide is possible.

 

Thanks, Chen. I need to dry it to avoid customers complaining about damp chromic acid. I guess I have nothing to loose from trying it, weigh up a small sample, the  after a week reweigh. Might start with calcium (I dont have phos pentoxide handy, although a  great choice. 

[exchemist]

19 hours ago, KOLM said:

Hi,

Have some chromic acid and it is very damp as it is very hygroscopic. Does anyone know of a way to dry it out? Maybe over conc sulfuric acid or anhydrous calcium chloride? Could not find anything on the internet. 

Thanks.

Are you referring to chromium trioxide? 

[chenbeier]

1 hour ago, exchemist said:

Are you referring to chromium trioxide? 

Chromium-VI-trioxide CrO₃ is called in publics mouth as chromic acid.

If it get wet  then it reacts to a sludge

n CrO₃ + H₂O => H₂(CrO₃)_(n-1)CrO₄

With n= 2 for example it will be H₂Cr₂O₇ Dichromic acid.

 

Edited June 1, 2024 by chenbeier

[exchemist]

15 minutes ago, chenbeier said:

Chromium-VI-trioxide CrO₃ is called in publics mouth as chromic acid.

If it get wet  then it reacts to a sludge

n CrO₃ + H₂O => H₂(CrO₃)_(n-1)CrO₄

With n= 2 for example it will be H₂Cr₂O₇ Dichromic acid.

 

OK thanks.  

[KOLM]

On 6/1/2024 at 11:07 AM, chenbeier said:

Chromium-VI-trioxide CrO₃ is called in publics mouth as chromic acid.

If it get wet  then it reacts to a sludge

n CrO₃ + H₂O => H₂(CrO₃)_(n-1)CrO₄

With n= 2 for example it will be H₂Cr₂O₇ Dichromic acid.

 

Wow, Chen, I didnt know. So, even if I were to dry it out some, it would not revert back to CrO3? 

[chenbeier]

6 minutes ago, KOLM said:

Wow, Chen, I didnt know. So, even if I were to dry it out some, it would not revert back to CrO3? 

Correct, it's difficult to keep it dry after open the container.

Edited June 3, 2024 by chenbeier

[KOLM]

2 hours ago, chenbeier said:

Correct, it's difficult to keep it dry after open the container.

Meaning, to clarify, once damp, it is not anymore CrO3, but a different compound H2Cr2O7 (?). 

[chenbeier]

CrO3,  H2CrO4, H2Cr2O7, etc. All are chromic acid.

 

On 6/1/2024 at 4:04 PM, exchemist said:

Are you referring to chromium trioxide? 

 

[KOLM]

Thans again, Chen. That helps.