nossr50 plans on reworking/rewriting the entirety of Alchemy in 2.2, due to difficulties with the current code.
Alchemy is about brewing potions. It provides a speed increase in the potion brew time, as well as the addition of new (previously) unobtainable potions.
Experience in Alchemy is gained by successfully crafting potions and by adding additional ingredients to existing potions.
Catalysis speeds of the brewing process, with a max speed of 4x at level 1000. This ability is unlocked at level 100 by default.
Concoctions allows brewing of more potions with custom ingredients. Which special ingredients are unlocked is determined by your Rank. There are 8 ranks to unlock.
|Tier 1||Blaze Powder, Fermented Spider Eye, Ghast Tear, Redstone, Glowstone Dust, Sugar, Glistering Melon, Golden Carrot, Magma Cream, Nether Wart, Spider Eye, Suplhur, Water Lily, Pufferfish (Vanilla Potions)|
|Tier 2||Carrot (Potion of Haste)
Slimeball (Potion of Dullness)
|Tier 3||Quartz (Potion of Absorption)
Rabbit's Foot (Potion of Leaping)
|Tier 4||Apple (Potion of Health Boost)
Rotten Flesh (Potion of Hunger)
|Tier 5||Brown Mushroom (Potion of Nausea)
Ink Sack (Potion of Blindness)
|Tier 6||Fern (Potion of Saturation)|
|Tier 7||Poisonous Potato (Potion of Decay)|
|Tier 8||Regular Golden Apple (Potion of Resistance)|