itch.io

Yeah, the puzzle throws a curve ball at you: basically, the recipe listed is for a hi-potion, and it warns you about creating an acid on accident (which is, incidentally, what Erica needs).

Specifically, it tells you that to create the acid, you must mix the first intermediate chemical (created by mixing "s. juice" and "korett") with something that has the same COLOR as the second intermediate.
Basically, the logical steps are:
1) Mix the second intermediate ("silverine" + "galbanos") to see what color it turns into (a bright orange hue);
2) Examine the chemical descriptions until you find something of a similar color ("solidus" is orange);
3) Mix the first intermediate ("s. juice" + "korett");
4) Add solidus and obtain the acid.

Note that you can just mix "s. juice" + "korett" and then add "solidus" to skip the first few steps if you already know the answer.