Formulae are alchemical recipes for creating potions, oils and bombs. Each formula lists the required ingredients and describes the type of base necessary to create the mixture. These recipes are typically acquired by reading scrolls, but some may be acquired through word of mouth, i.e. by speaking with certain NPCs.
In addition, they can be learned by alchemical experimentation during meditation and subsequent usage with exception of fisstech which requires only experimentation.
In third game formulae appear in your journal on same spot as crafting diagrams. Player begin with several default schematics and recipes and then purchase or find more during playthrough.
Since Patch 1.07, you can "pin" any given formula and this will cause the list of items needed to craft the formula to appear in the shop panel, making it easier to keep track of what you still need to acquire. Because there is giantic number of torn-out pages, formulae and manuscripts they are not listed here but found in special category.