In organic chemistry we use molecular sieves (4A Beads) for drying of organic solvents. I want to know how to confirm the threshold limit beyond which the molecular sieves (4A Beads) cannot be reused further?
Dry them, then on a glass of water and a thermometer add a bunch. You should see a considerable rise in temperature, if the termperature doesn't change, they're done for.
I was hesitant to post a youtube video in an academic forum but...he explains it very well.
https://www.youtube.com/watch?v=MduzjhRHBFY
In addition to suitable Adel Amer answer. ->
Molecular sieves 3A are better over 4A in common solvent drying, but costly in lab catalogs. However, available everywhere and very cheap PHONOSORB ® 555 ( adsorbent for insulating glass units) is exact dry, ready to use 3A molecular sieves!
In addition to Tomás Allende answer ->
Molecular sieves 3A validation: wetting with 1/6 water (by weight) should rise temperature ~ 30 - 34oC
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