Harry Potter and the Chamber of Secrets Walkthrough
Cauldron and Vial Locations

It's important to find vials and keep them filled. That is one of your key ways of healing. You get your first vial in the alley as you shop before you head off to school. You're instructed at this point how to use the cauldron in the shop.

There are 2 cauldrons in the school. One is in the greenhouse - you find this one when doing your search for the Diffendo spell on the second night. You use that diffendo spell to get to the second cauldron. From the 2nd floor, cut the tapestry open and go behind it. On the right is a room with a cauldron in it.

Once you can earn 80 beans to buy the lock-opening spell from the shop, go down under the main entry stairs, to the left. There's a locked chest down there with another vial for you.

Harry Potter and the Chamber of Secrets Walkthrough, Tips and Techniques