Board Thread:Questions and Answers/@comment-94.208.134.40-20130126101531/@comment-6077852-20130128015823

Put it in your hotbar (where you put items you want to use) then select the alchemical bag in the hotbar and right-click. This should open the alchemical bag, if it doesn't then you are either doing it wrong or there are server issues (if you are in SMP).