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.

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.

 

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. 

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? 

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, 20241 yr by chenbeier

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.  

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? 

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, 20241 yr by chenbeier

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 (?). 

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

 

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

Are you referring to chromium trioxide? 

 

Thans again, Chen. That helps.