Dimethylglyoxime crystals, images and a question

[banania]

Hello,

there is a recent post by mtuell where he shared his discovery that dimethylglyoxime crystallizes with interference colors. mtuell told that he had used methanol as solvent and just let the saturated solution dry out on a slide and it crystallized nicely with intereference colors.

Dimethylglyoxime is soluble both in methanol and acetone. I have that stuff in pulverized form (99% reagent grade) and used acetone as methanol was not available. For some reason saturated acetone solution did not crystallize at all. Whatever I tried just gey dust was left on the slide.

So I tried to crystallize the stuff without dissolving it first and heating the pulver crystallized it very easily. Also melting it resulted in crysallization when cooling down. But dissolving these crystals in acetone left again just grey pulver on the slide. Does anyone have a explanation for this or a tip how to make the solution crystallize? I am a little uneasy about this kind of heated cooking in our kitchen as I am no chemist... exploding slides and unknown fumes

Anyway I was able to crystallize the stuff flat on a slide by melting it between slides and it produced some nice shapes and colors.









Crossed polarizers, Nikon 10X 0.25 with 100mm tube lens.

Henri

[Troels]

Very dramatic and impressive pictures.

Troels

[banania]

Thanks Troels,

dimethylgyoxime was a nice find from mtuell.

[abpho]

Sweet. Very epic.

[mtuell]

Very dramatic! I see some of the crystal forms I originally found. What I found so interesting was the wide variety of shapes I obtained. I'll have to try your melting technique, too.

I took another sample of my dimethylglyoxime crystals saturated in methanol and tried again. I got similar results, but not identical to the first go-round.

In PM, you mentioned that you filtered your saturated acetone, but I didn't filter my methanol. I'm wondering if the difference is that you removed seed crystals? Also, I let it evaporate under a cover slip. While watching it evaporate this time, I noticed some truly ridiculous fluid/thermo dynamic effects near the liquid boundary. There are some insane forces happening on the microscopic level, causing convection currents to whip little crystals around and even spin in place! I'll have to try this again and get some video.

Thanks for trying and posting your results!

Mike

[banania]

Thanks abpho&mtuell.

I tried to use nonfiltered stuff and also to crystallize the solution between slides, both cold and heated, but no success. This failure remains a bit of a mystery. I'll have to buy some methanol, if I can find a supplier for small amounts.

[zzffnn]

Nice images, Henri.

You probably should not try melts, if you don't know a bit of chemistry.

What mtuell did not mention (and probably assumed that everyone knows) is that methanol is toxic.

Acetone is much safer.

In drug stores of USA, you can buy 91% isopropyl alcohol cheaply. That is closer to to methanol, than acetone, in terms of chemistry. I have tried that to dissolve medicines and recrystallize them for polarization microscopy. Acetaminophen or vitamin C - I cannot remember which one - worked very well.

Each solvent is different in terms of crystallography chemistry. You would need an experienced chemist to explain exactly why reagent A works and B does not. Much easier to try.

But before you try, please look up safety and toxicity information of each chemical.

[banania]

zzffnn, thanks for your tips and advice. I have crystallized various substances and used various solvents, but don't know much chemistry. That's why I would much prefer to use safe stuff like acetone, water or methanol, which should of course not be consumed. Otherwise I didn't consider it as toxic. I have also isopropanol, not pure stuff, but as a mix with glycol, and also fairly pure as an antiseptic, and I have tried also these on various substances, but not much is soluble in that stuff. Just now trying isopropanol + dimethylglyoxime but it doesn't seem to be soluble in isopropanol.

Safety regulations here in Finland are really strict, it is difficult to buy chemicals. Even stuff like 90% isopropanol is unavailable and regulated so must buy instead antiseptics or the legal 30% isopronanol + water mixture or try your luck with various isopropanol based freezing prevention liquids. The same with methanol, for which I have a supplier, but the minimum amount is 20 litres, which is an unpractical amount for my tiny working space. It is hard not become a mad scientist when stuff has to be improvised.

Maybe I should try dimethylglyoxime in heated acetone and add a very tiny amount of paracetamol or maybe urea to start the crystallization process... here we go again...

[zzffnn]

You probably don't want to breath in or contact (with naked skin) methanol very often. Consuming it may blind or kill a person.

[mtuell]

Yes, that is certainly true. Acetone isn't good for you, either, but methanol is worse. Reading the SDS, a first aid measure for ingestion is to chase it with a big glass of whiskey (or other 80 proof ethanol)!

But, in all seriousness, one should obtain Safety Data Sheets for all chemicals in your possession or even if you are considering getting some.

40L? Dang! I've got a 4L bottle, and I thought that was big!

Dimethylglyoximie itself is very stinky, but not terribly toxic. It is however potentially flammable at high temperatures, so keep that in mind!

I'll have to try saturating it in acetone, and see what happens. I have regular stuff from the hardware store, but I think at work there is some HPLC or reagent grade, which would have less water content.

Good luck, and stay safe!
Mike

[ChrisR]

I got some methanol from a model aeroplane person's shop. I daresay it's not lab grade, but maybe doesn't need to be.