[rpsly]

I need to make an odorless DMSO.  From what I understand, DMSO contains a small amount of DMS which is the garlic smell that I don't want.  Since DMSO has a boiling point of 189 C and the DMS has a boiling point of 37 C, can I just boil off the DMS and leave me with odorless DMSO? 

[discodermolide]

Why not place it under a slight vacuum which should remove the DMS.

[rpsly]

I found this in an older post and it seems to be what I was looking for,

The compound responsible for the smell is DMS (dimethylsulfide), a gas that almost always accompanies DMSO in very minute quantities. DMSO itself is odorless, so any smell you detect is coming from DMS or chemically related sulfides. Generally, DMS is a by-product of the DMSO synthetic process and is so commonly associated with DMSO that people often attribute the bad smell to DMSO itself.

Since it is gaseous, DMS is very difficult to trap even with a liquid nitrogen trap, as suggested above. You are better off treating the exhaust of your vacuum pump so that any DMS gas that passes through is neutralized before it can offend your nostrils. I would recommend attaching one end of a plastic or rubber hose to the exhaust of your vacuum pump. Stick the other end of the hose into a solution of household bleach (i.e., Clorox) and water. The bleach will oxidize the DMS back into DMSO and get rid of the smell.  When working with sulfides in organic chemistry, it is usually necessary to wash all lab equipment with a bleach solution to get rid of the foul odor. Spoiled food products and human waste contain similar sulfides, so its no wonder the odor has been troubling you. I would hasten to add that the actual amount of DMS we are talking about here is very tiny, so there is virtually no risk of being harmed by it or the bleach solution once it has been used to neutralize the exhaust gas.

A suggestion for the bleach concentration is something like 9 parts water, 1 part bleach. It doesn't take very much to neutralize DMS chemically. Just make sure the exhaust tube is completely submerged in order to assure all of the gas passes through the bleach solution before escaping into ambient air.

[popbop]

Hi rpsly,

I know this is a very old thread, but I'm not clear on how you ended up removing the DMS from the DMSO.

Did you use only vacuum to pump out DMS into neutralizing chlorine bath, did you boil off the DMS, or did you use a combination of heat and vacuum to do the job? And, at what vacuum did you extract the DMS?

I'm going to attempt the same here with the usual 99.9% DMSO you can purchase all over the internet.

Thanks!

Pop

[Dan]

rpsly's account has been inactive for 2 years, I doubt you will get a response.

[Furanone]

Hi rpsly,

I know this is a very old thread, but I'm not clear on how you ended up removing the DMS from the DMSO.

Did you use only vacuum to pump out DMS into neutralizing chlorine bath, did you boil off the DMS, or did you use a combination of heat and vacuum to do the job? And, at what vacuum did you extract the DMS?

I'm going to attempt the same here with the usual 99.9% DMSO you can purchase all over the internet.

Thanks!

Pop

I would recommend first trying vacuum only since boiling point of DMS is very low (~37.5 C) and why risk possibly forming more? I am not sure you will even be able to remove odor completely simply because even in the tracest amounts sulfur volatiles tend to be the compounds most sensitive to the human nose (eg skunk odor and why they add a trace sulfur compound to natural gas to allow olfactory detection for gas leaks). Please let us know if you are successful -- I would be interested to know!