Those little packs (desiccants) are meant to maintain a dry environment in a small container that was dried before it was sealed. Uncooked rice grains do essentially the same thing, that's why people add them to salt shakers (so reduce humidity that might otherwise clump the salt crystals). So they're no use for drying anything other than a tiny popcorn bud in a pill bottle. But once you've finished curing your grow, it wouldn't hurt to stick one or two in a jar...they're perfectly safe (just silica,or sand), and they may help to prevent mold growth if you sealed the jar just a little too soon.
Some of the packs are colored. Usually a blue color means they're still useful. But if they're purple or even fully red, sometimes they can be regenerated by heating them. More useless information I guess, but the point is, don't try to use them to dry your crop, it's a waste of time.
