Anyone know about dry grains/granules?!

In medication bottles, dried flowers, new leather cases, and so on they often put tiny bags with small grains in them that attract fluids so that things don't get moldy n stuff!.
Does anyone know the official name of this please!?
Maybe you also know where one could acquire these in larger quantities (I know a search engine will help but it's not that useful if I don't know the correct term)!.Www@FoodAQ@Com

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