Potion of see invisible

From Wikihack

The potion of see invisible enables you to see invisible monsters. Blessed potions give you the intrinsic permanently; uncursed and cursed give you the intrinsic for a number of turns.

This potion also unblinds you if you were previously blind.

When drinking this potion, you receive the message "This tastes like [fruit; default is slime mold] juice." The potion of fruit juice has the same message; these are therefore difficult to tell apart by random quaffing. Some ways to tell the two apart include:

• If you were blind and were unblinded, it was see invisible.
• If you see previously invisible objects/enemies after quaffing, it was see invisible.
• Zap a wand of enlightenment or otherwise attain enlightenment. If you have the see invisible intrinsic, it was see invisible.
• Fruit juice is sold in a delicatessen; see invisible is not. If you see one of the two in a deli, it's fruit juice. Likewise, if a deli buys the potion, it's fruit juice. A delicatessen shopkeeper will not buy see invisible.
• Dipping a unicorn horn into a potion of sickness turns it into fruit juice.
• Dipping an amethyst into a potion of booze turns it into fruit juice.
• Cancelling a potion of sickness or see invisible turns it into fruit juice.
• If you are on the border of a hunger change and it disappears upon quaffing, it was fruit juice; however, this is difficult to test.