Does propanone go 'off'?

[Alex C]

I have a teacher looking at polymers next week so just setting up some demos (making nylon, hydrogel granules and water, hair gel and salt, polystyrene and propanone)

I don't know why but maybe cause the polystyrene we have is getting a bit old and isn't 'crispy' any more I thought I'd test a bit in some propanone to check it bubbled and collapsed into a blob.....well it didn't. I was ready to blame the old polystyrene so grabbed a new polystyrene cup....still nothing. I then got some new propanone from the stock bottle in the flam store and abracadabra it worked, so definitely the propanone misbehaving. This isn't a bottle that goes out in classes just a little bit decanted into a reagent bottle in the prep room flam cupboard for those odd jobs that come up so I don't think it is contaminated and it still smelled like propanone. Anyone have any thoughts as to why it isn't doing what I expected?

 

[Deleted member 31094]

It could possibly be a propanone solution. One of the A level pracs uses a 1M propanone solution

 

[Medchemist]

acetone will evaporate but i've never heard of it going off

 

[Nabi]

Maybe it's the water content in an old batch? Acetone is quite hygroscopic. I remember having to dry acetone with a drying agent in the past.
I would add some anhydrous calcium chloride to the old batch and, after allowing some time to dry, retest it.

 

[Phil_C]

If it's been used for rinsing wet glassware and recycled over and over it could be mostly water!

 

[Medchemist]

If it's been used for rinsing wet glassware and recycled over and over it could be mostly water!

This is a good point, although it begs the question which godless soul put the washings back in the bottle

 

[karen b]

This is a good point, although it begs the question which godless soul put the washings back in the bottle

Well, if you “know” that bottle is used solely for that purpose it wouldn’t matter. A label would be better though

 

[Alex C]

If it's been used for rinsing wet glassware and recycled over and over it could be mostly water!

Maybe it's the water content in an old batch? Acetone is quite hygroscopic. I remember having to dry acetone with a drying agent in the past.
I would add some anhydrous calcium chloride to the old batch and, after allowing some time to dry, retest it.

Never used for rinsing glassware but was stored in a glass reagent bottle with a glass stopper (not screw top bottle) so probably has just taken on water over time. Legacy to previous chemistry tech. The new propanone out of the screw top stock bottle worked fine. I'll try a bit of calcium chloride and see if it 'fixes' the propanone. Thanks all!