[Babcock_Hall]

I cannot find –20 mesh for less than $150 per 50 grams.  Will the coarser material will work as well as a drying agent for solvents such as DCM?  If not, could we grind it quickly in an oven dried mortar and pestle?  We plan to use the dry DCM for reactions involving triflic anhydride.  Obviously, another option is to buy 30 ppm DCM.  Thanks.

[discodermolide]

I think the coarse material will be extremely hard and you won't do it in a mortar.
Dry some 4Å sieves and use them to dry the DCM.

[Babcock_Hall]

Thank you.  Do we need a vacuum oven to dry the sieves, or will an ordinary oven do the trick?

[discodermolide]

Use a vacuum oven if you can.
But you can heat them to 500°C or more and re-cool under argon. We qualified such a process for a GMP step.

[Babcock_Hall]

We don't have a vacuum oven, and I don't think our regular ovens go that high.

[discodermolide]

Use a bunsen burner.

[TheUnassuming]

We don't have a vacuum oven either, so I usually heat them with a torch under high-vac.  It works great, just be careful heating up a flask under high-vac.  A post-doc in the hood next to mine was doing this once but kept the torch pointed at one point too long and the RBF distorted and dimpled in.

[Babcock_Hall]

"Molecular sieves must be activated (dried) before use. To check if molecular sieves are
dry, you may put a bit in the palm of your hand and add a touch of water. If they generate
a good amount of heat, they are dry. Otherwise, follow the procedure below:
Add molecular sieves to a dry flask and heat to 120 °C with an oil bath under high
vacuum overnight (no stirring needed) using a flow control adapter (t-joint). Refill with
argon, and use as needed (remember to flush flask out by vacuum-argon-vacuum-argon
after opening each time to keep water out). Check sieves periodically for heat generation
and dry as needed."  Someone sent me this which can be found at Cornell:  http://collum.chem.cornell.edu/documents/Molecular_sieves_activation.pdf