fasa precip in clean xylene?

[rootsie]

So... I was getting ready to do my first fasa on some fresh xylene pulls from an acrb a/b. When I just tested my prepared fasa (I made it yesterday and let it sit overnight) on some clean xylene straight out of the jar, the fumeric precipitated in a cloud. I thought that wasn't supposed to happen with xylene--that it should only precip once it reacts with something like dmt. And that you would know you're done when there's no more clouding.

All my chems should be quality. Anhydrous acetone. Pure, food grad fumeric. ACS reagent grade xylene...

Xylene states 98.5% minimum with:
22.02% paraxylene
46.67% metaxylene
13.73% orthoxylene
17.47% ethyl benzene

Any thoughts? Much thanks for any assistance!

 

[endlessness]

hmmm thats really weird...

Do you have IPA? Would be interesting to see if FASI works with your xylene.


Also, could you repeat the process with fresh FASA and xylene and see if same happens or if it was a weird fluke?

Im not sure if those other solvents mixed in your xylene will screw things up like ethyl benzene, maybe thats the culprit too..

 

[rootsie]

Thanks for the ideas endlessness!

Update: I got some fresh 99.9% IPA and made some FASI. Made another small batch of FASA too. Additionally, realized I had some d limo on the shelf. Time for some experiments...

New FASA:
Xylene - clouds instantly, slowly precipitates.
D limo - clouds instantly, slowly precipitates.

FASI:
Xylene - very slight haze that hovers but doesn't drop crystals.
D limo - no clouding, solution remains clear.

But then I got curious and decided to add FASA after the FASI above:
Xylene - no additional clouding/haze.
D limo - no clouding.

This all gives me several thoughts. First, I think something's up with my xylene that it precips. So I think I'll go with FASI on my pulls tomorrow night. Is there any real advantage/ difference using FASA vs FASI?

Second (and I'm not sure why or how this might be applied), it seems you could mix FASI and FASA to use with d limo. Would there be any reason to not mix these solvents (or any reason to do it for that matter)?

Finally, I was thinking of switching to d limo for subsequent pulls on this same batch. Would there be any potential issues with changing the pulling solvent mid course?

 

[rootsie]

FASI worked just fine:thumb_up:

I'll post some lab notes in a new thread at some point.

 

[geko]

So... I was getting ready to do my first fasa on some fresh xylene pulls from an acrb a/b. When I just tested my prepared fasa (I made it yesterday and let it sit overnight) on some clean xylene straight out of the jar, the fumeric precipitated in a cloud. I thought that wasn't supposed to happen with xylene--that it should only precip once it reacts with something like dmt. And that you would know you're done when there's no more clouding.

All my chems should be quality. Anhydrous acetone. Pure, food grad fumeric. ACS reagent grade xylene...

Xylene states 98.5% minimum with:
22.02% paraxylene
46.67% metaxylene
13.73% orthoxylene
17.47% ethyl benzene

Any thoughts? Much thanks for any assistance!

The same here - lab grade Xylene (99.9%), lab grade anhydrous Acetone (99.5%), lab grade Fumaric Acid (99.4%) and the drops produce slight white haze, some of which slowly precipitates, while the rest stays in suspension so the solution remains milky. The test was done with 2 ml of Xylene and 4-5 drops of FASA, so that my guess is that the Fumaric Acid precipitates. But it shouldn't. Any thoughts?

 

[downwardsfromzero]

It's a bit cheeky for the manufacturer to be claiming 98.5% xylene when in fact there's only about 81% (I know, they're allowed to as it's incredibly tricky to separate off the ethylbenzene!) It does make me wonder if better results would be achieved straight off the bat with et-benz free xylene.

All that asides, you've got some interesting data points there. I would definitely suggest to all those out there who would want to try this method that precipitation of your fumaric acid can be avoided by pre-dosing your xylene or limonene with a little IPA, or with acetone if that's what you have.

 

[geko]

It's a bit cheeky for the manufacturer to be claiming 98.5% xylene when in fact there's only about 81% (I know, they're allowed to as it's incredibly tricky to separate off the ethylbenzene!) It does make me wonder if better results would be achieved straight off the bat with et-benz free xylene.

Don't know what Rootsie used but my xylene has a test analysis of the batch which lists 99.9%, it's a lab reagent. Still clouds from pure FASA. I don't know what to make of this.

All that asides, you've got some interesting data points there. I would definitely suggest to all those out there who would want to try this method that precipitation of your fumaric acid can be avoided by pre-dosing your xylene or limonene with a little IPA, or with acetone if that's what you have.

This is very interesting! By pre-dosing the xylene you mean to introduce IPA before or after the pull? I presume after the pull and just before adding FASA, right? Would the IPA and Xylene mix well?

And last question, since you seem to know your stuff - does 99% IPA for FASI usually need drying if it is from an already opened container (i.e. how hygroscopic is it)?

 

[downwardsfromzero]

That's exactly what I mean by pre-dosing. Add a little of your chosen solvent before adding FASX. I can confirm that this works.

Freshly dehydrated solvent is always better, both acetone and IPA are hygroscopic. The longer it is since you opened your IPA container, the greater the water content (up to 9%, of course, which is the 91% IPA azeotrope) unless you've handled it under very carefully controlled conditions which won't happen outside of a lab - unless you work in a lab and know how to do this at home.

As far as it goes with drying your solvents, I don't know how long you've had them - so just apply standard procedures. It shouldn't take so very long to get a technically usable result. Lab methods for really dry alcohol don't involve using magnesium sulphate anyhow.

 

[geko]

That's exactly what I mean by pre-dosing. Add a little of your chosen solvent before adding FASX. I can confirm that this works.

Freshly dehydrated solvent is always better, both acetone and IPA are hygroscopic. The longer it is since you opened your IPA container, the greater the water content (up to 9%, of course, which is the 91% IPA azeotrope) unless you've handled it under very carefully controlled conditions which won't happen outside of a lab - unless you work in a lab and know how to do this at home.

As far as it goes with drying your solvents, I don't know how long you've had them - so just apply standard procedures. It shouldn't take so very long to get a technically usable result. Lab methods for really dry alcohol don't involve using magnesium sulphate anyhow.

Thanks very much for the input! This would basically mean that we could do this with a solvent which is just not saturated. Interesting...