Sciencemadness Discussion Board

adding nitrogen to dcm /chloroform

itsafineday - 10-12-2019 at 16:15

Would adding nitrogen from a tank to a bottle of dcm or chloroform help to increase shelf life?
I don't have a valve to evacuate and then fill the bottle I plan on just putting the hose end into the uncapped bottle , releasing gas for 10 seconds or so and then capping the bottle.

Also, how dangerous would a bottle of chloroform be after about 6 months or a year sitting in a closet at 27-30 c max ?

DavidJR - 10-12-2019 at 16:35

Probably would help, yes, but I don't think it's necessary. I'm assuming though that you are just concerned with the safety aspect of phosgene formation, rather than worrying about trace amounts affecting sensitive HPLC/GC analyses etc.

Checking my commercial solvents, the dichloromethane was supplied stabilized with 0.1% methanol and the chloroform was supplied stabilized with 0.5% ethanol. I haven't noticed any hay odour or anything like that after storage in amber glass - over a year for the chloroform in a part-empty bottle. My lab is quite cold for most of the year though. I haven't conducted any specific analysis for degradation products though.

If you made the chloroform yourself I would definitely add 0.5% to 1.0% of ethanol. I probably wouldn't worry about dichloromethane even if unstabilized, because it is a lot more stable. Store them in a tightly-capped amber glass bottle away from sunlight.

[Edited on 11-12-2019 by DavidJR]

itsafineday - 10-12-2019 at 16:38

Thanks DavidJR. That was a very helpful answer.

DavidJR - 10-12-2019 at 16:52

For peroxidizable solvents like diethyl ether and tetrahydrofuran, it is probably more beneficial to purge the headspace with inert gas. Especially if the solvent does not contain a stabilizer like BHT. Peroxide formation in ethers can be quite rapid.

LearnedAmateur - 7-1-2020 at 05:16

The worst thing that’s ever happened to me with DCM, is that a small HDPE bottle (not completely airtight) with ~50-100mL, evaporated over the course of about 2 months.

I’d had a litre of the stuff for around 8 months, no noticeable change in chemical properties (as a solvent, nor via the trusty old smell test). Not something to worry about like you would with ethers.

[Edited on 7-1-2020 by LearnedAmateur]

draculic acid69 - 7-1-2020 at 05:46

I had an old 4litre can of the stuff an by the time i got to the bottom of it 2-3yrs or thereabouts there was a rusty water layer in the bottom.the stuff on top was still good
though.worst case scenario is some breaks down into water methanol and HCL with some phosgene bubbling out over the years.dont keep it in your living space that's all.
This takes years to happen so don't worry about it too much.

[Edited on 7-1-2020 by draculic acid69]