RuneScape Classic Wiki
The main RuneScape Wiki has an article on: Snakes Weed Solution
The Old School RuneScape Wiki also has an article on Snakes Weed Solution.

Snakes Weed Solution is a quest item which is used in the Legend's Quest. It is created by using Snake Weed on a vial of water. Ardrigal may be added to it in order to produce the Gujuo Potion after Gujuo teaches you how to make the potion during the Legend's Quest.

Adding Ardrigal to a vial of water similarly produces an Ardrigal Solution to which Snake Weed can be added in order to make the Gujuo Potion. Since either method produces the same result, the order in which players add the herbs to water does not matter.


Creating this item:

You put the Snake Weed herb into the watervial[sic].
You make a solution of Snake Weed.