The Alchemical Bag is an item from the Equivalent Exchange 3 mod. It can't be crafted like it was in EE2 yet, and is therefore only accessible by the NEI Interface. For this reason, the bag currently has no function. It still comes in all sixteen colors as it did in EE2. When open, it shows 56 inventory slots that are not yet accepting items. The bag changes to an open animation when opening a chest or the regular inventory, but it otherwise is unable to do anything.
The bag currently has no recipe, it can only be acquired in game by cheating, and does not hold items even if it is cheated in.