A little something I have been using in my games. Just thought I'd share. You might like them, you might not. Use them as you will.
Potion of Tongues
This potion allows the person who drinks it to read, speak and understand any language.
The potion comes in a heavy crystal vial with 3 notches marked on
it dividing the vial into 4ths. If a character drinks 1/4th of a vial,
the potion will work for 15 minutes. Each 1/4th of a vial that is
taken, is good for 15 minutes with the whole potion good for 1 hour.
However, After the potion wears off, the character will remember
nothing of what was said, heard or read. Any witnesses will be able to
remember and the character can write things down if possible, but they
will have no memory of the communications at all.
The Everfull Option
If any potion is obtained from a trapped location or from a high
level source, this option allows for the DM to determine that there is a
1d10 percent chance that the vial in question is an "Everfull" vial.
This means that once the vial has been emptied, capped and put away for
24 hours, when it is pulled out again, it will have been magically
refilled with the same potion.