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Chemistry Forums for Students => Organic Chemistry Forum => Organic Chemistry Forum for Graduate Students and Professionals => Topic started by: Geoffrey Smith on June 26, 2014, 09:00:50 AM

Title: precipitate in DMSO
Post by: Geoffrey Smith on June 26, 2014, 09:00:50 AM

I've just noticed a clear crystalline precipitate in my commercial bottle of 99.5% dimethyl sulfoxide (CAS 67-68-5).  I assume the reagent is now bad, but what is the ppt.? 

Title: Re: precipitate in DMSO
Post by: opsomath on June 26, 2014, 09:27:09 AM

I'm guessing the air conditioning has been coming on a lot lately. DMSO freezes around the temperature of a cool room; your precipitate is solid DMSO.

Title: Re: precipitate in DMSO
Post by: kamiyu on June 26, 2014, 10:41:26 AM

Yeah, I agree. Indeed, this is called "partial freeze" and this is used for purification of ethanol (well, you may say concentrating ethanol). The solid part contains purer DMSO, which means less water contained in it.