Script help

[PutraenusAlivius]

''Allows the player to combine items in his inventory.''

I'm not trying to do that.

The pot is on the table. You are not going to pick up the pot in any part. Once you have put all the chemicals into the pot, (which by the way has a script area on it, with item interaction on called GetAcidComplete)
So you don't exactly put the chemicals into the pot, you put them into the script area which has item interaction on. After successfully putting all four chemicals into the script area, the script area will disappear, allowing you to take the full chemistry pot to your inventory.

I'm sorry for not mentioning that earlier.

Then you use AddUseItemCallback then.