[Cesium-137]

Maybe I'm looking in all the wrong places, but it seems that a standard procedure for activating/reactivating 4A molecular sieves doesn't exist. I filled a 250 mL round bottom just under half full, put it under the Hi-Vac and heated it with a snug heating mantle to 260 C for 6ish hours. I let it cool, purged the flask under Ar and capped it with a septum wrapped in parafilm. Judging by the exotherm created when I added a drop of water to some sieves, they were activated... My procedure just seems very extraneous to me, and because there seem to be no standard procedures for this, I'd like to start one. Anyone have a procedure that activates or reactivates 4A sieves? Is my way overkill? Thanks!

[macman104]

I reactivate them in an oven that is only at about 190C I believe.  I usually let them sit in there for a few days, then transfer to a dessicator to cool down, once cooled, cap and leave in dessicator to use.

[g-bones]

you could always just flame dry them under vacuum in your reaction vessel before use.  I agree with macman, its easy enough to just keep some around in  the oven for when you need them.

[dunno260]

We keep ours in a 170C oven and that keeps them working well enough even in the humidity of the deep south.

[macman104]

oh, I also noticed that you capped the vessel with a septum.  Septums are good for short term storing, but in our lab, the general consensus is that long term, they will slowly leach air/moisture into your system.  Not sure if you used the vessel right away, or if you are storing the seives long term in there, but something to consider.

[wpenrose]

Heat at 170 C in a vacuum oven and cool it in a desiccator. So prepared, it will suck the water out of anyone standing within 50 feet.

Be careful of excessive heat; the zeolite structure will eventually break down.

Dangerous Bill