Attention****The mod is currently in work. All mod files, as well as description, will change significantly as updates occur.
If you are looking for a complete mod for regular play
you are better off using the original Primer Alchemy (Next Gen version) from skyliner390.
General Info
Involved Alchemy is modified version of original skyliner390 mod - Primer Alchemy, The main idea of this mod is to minimize changes to Primer Alchemy that are not related to the updated alchemical item creation system. In other words, the new alchemy is partially less different from the vanilla game. A description of general functionality can be found in the description of Primer Alchemy or below in this description (section of outdated versions of Involved Alchemy).

Notes:

1. There are two mods with remade alchemy from skyliner390: Primer for Old Gen game version and Alchemy for actual Next Gen game version. In this description, “Primer Alchemy” refers to the Next Gen version unless otherwise noted.
2. It is assumed that you are already familiar with some version of Primer Alchemy. Otherwise, please check out the original mod page. This description will be updated in the future to make it clearer for everyone.
3. Involved Alchemy has never existed as a mod for Old Gen version of the game, and there are no plans to create such a version in the foreseeable future.
4. Alchemical items in the description mean potions, decoctions, oils and bombs, which can be created by player. 

Involved Alchemy version 1.2.3/1.2.4Outdated versions of mod. Initially developed by SiccW33d based on Old Gen Primer version 1.20.3. Involved Alchemy versions 1.2+ does not work in actual game version, the lastest supported game version is 4.01. Most likely, this “old generation” of versions will not be updated at all in the future. This is due to drastic changes in Next Gen Primer Alchemy, which have significantly improved it in terms of compatibility with the game and possible merging problems with other mods.

Involved Alchemy version 2.0aInvolved Alchemy versions 2.0+ is a "new generation" of mod, that is reworked using Next Gen Primer Alchemy as the basis. It is planned that this mod will follow the current Primer Alchemy updates. New Involved Alchemy will include both changes that were created in mod versions 1.0+ and new ones. The full list of changes implemented in the latest version of the mod is given below.

Actual mod version 2.0a is alpha version of 2.0+, which contains only part of the planned changes. It based on Primer Alchemy version 1.04 and runs on game version 4.04.

Detailed list of changes Involved Alchemy vs Primer AlchemySpoiler:  Show
Global changes
1. Returned toxicity offset from decoctions as a separate value. Digestion with decoctions works similarly to potions: toxicity offset gradually increases over time.
2. Basic digestion time is divided for potions and decoctions.
3. An excretion effect has been created, which is applied automatically after the end of decoction and gradually reduces toxicity offset, similar to the digestion effect.
4. The toxicity calculation system when checking that a potion can be used has been changed. 
Thus, firstly, the error where it was impossible to use a potion with a sufficient amount of free toxicity was fixed. For example, there have been cases when it was impossible to use potion (25 tox) after using a decoction (50 tox) and a potion (25 tox) with a maximum 100 toxicity.
Secondly, if toxicity is close to maximum, this makes it possible to use a new potion earlier, without waiting for the moment when the toxicity decreases to the threshold value.

Changes to the properties of alchemical items 1. White Honey - the working principle of the potion has been changed. Immediately after use, it removes all active effects from potions, including digestion and excretion effects (with the exception of the Wolf Hour.) After this, it gradually reduces all toxicity that was present at the use moment (both regular and offset foxicity). This is shown in the interface as a digestion effect. The effect will be instantly removed if the toxicity was zero at the use moment.
White Honey now clears toxicity completely regardless of item level, however the processing (digestion) time is different. For regular item it is 4 times the basic digestion time, for enhanced version it is the same as the basic time, for superior it is 25% of the basic value.
2. White Raffard Decoction - digestion time is 25% of the basic digestion time for all potion levels.

Interface changes
1. The correct display of the superior White Raffard Decoction effect (temporary invulnerability) has been returned.
2. The display of the potions/decoctions effect related to vitality regeneration in battle has been returned. Please note that the localization of the description of this effect is incorrect. This is a bug in the vanilla game.

Mod settings changes1. Changed settings group ID to separate Involved Alchemy settings from Primer Alchemy settings. To find the mod settings in the user.settings file, look for the "InvolvedAlchemyMenu".
2. A new setting has been added that controls the digestion time of decoctions.
3. The potion digestion time setting range has been changed. Set to default value 10 for potions and 30 for decoctions.

Localization changes
1. In the lines associated with the mod name, Primer is replaced with Involved Aclhemy. 
2. Lines associated with decoction duration modifiers have been changed.
3. Added new lines related to separate digestion of potions and decoctions.

Other changes
1. The names of the mod folder, dlc folder and mod settings file have been changed.

Work In ProgressAmong the general changes, it is planned to return the system for calculating toxicity and its effect on Geralt, as well as most of the changed skills to the state of the vanilla game. Also a number of smaller changes: interface, localization, etc. There may be some minor features added that don't feel like the vanilla game. The list of planned changes is in the pinned comment and will be updated.

Install and uninstallSame as Primer Alchemy. Read the instruction inside the mod’s root directory and follow them thoroughly. Please note that the mod affects saves. Be careful when uninstalling.

Compatibility with other mods and mergingPlease check out the Primer Alchemy compatibility details first.
For obvious reasons, using different versions of Involved Alchemy and Primer Alchemy is impossible. Do not mix files from different versions of these mods. General compatibility of Involved Alchemy may be slightly worse than the Primer Alchemy.

Highly recommended modsBrothers In Arms:  TW3 Bug Fix and Restored Content Collection. When merging .xml related to potion recipes, select the option that is linked to Involved Alchemy files.

CreditsThanks to skyliner390 for awesome original mod, without which this mod would not exist.
Thanks to ElementaryLewis for helping with some issues.

Thanks to weeketfull, Kezel and others who helped with testing older versions of the mod up to 1.2.3.Description for outdated Involved Alchemy version 1.2.3. May differ significantly from the new version 2.0a. Spoiler:  ShowOverview:

As much as I love The Witcher 3, the Alchemy is the weakest part IMO, all of these plants in this world and I hardly used them.
Here is Involved Alchemy,  a next-gen light version of ƤƦᎥოꂅᏒ by: skyliner390. Involved Alchemy is based on Primer version 1.20.3.
No changes to Decoction, Signs or Mutagens, just pure Alchemy.

The following is partially copied from : ƤƦᎥოꂅᏒ

Brewing:

There is no more automatic item refill when meditating. You will need to acquire all the necessary ingredients if you want to create something. To create alchemical items, you need to sit down by a fire. The mod features its own real-time meditation feature, which allows you to create one if you have enough firewood. For immersive mediating, use with Swords and Meditation.

Controls:Meditation
K/B&M
{Defaults: (Alchemy = L key) (MoveTimeFoward = Space key) (ExitMedState = L key) (MeditateWithCampfire = L Shift key)

To enter the meditation state, you need to tap the (Alchemy) key to make Geralt enter the meditation position.
To build a campfire, press and hold the (Alchemy) key for half a second and release it, or press the (Alchemy) key and tap the (MeditateWithCampfire) key to have Geralt enter the meditation position and spawn a campfire. Once in the meditation state, you can tap the (Alchemy) key again to enter the alchemy menu, or hold the (MoveTimeFoward) key to accelerate time while in meditation state. To exit the meditation state, simply press and hold the (ExitMedState) key.
}

Gamepad
{Defaults: (Meditate = Right Thumb) (MeditateWithCampfire = Right Trigger) (MoveTimeFoward = Left Thumb) (ExitMedState = Right Thumb)

To enter the meditation state, you need to press and hold the (Meditate) key for half a second and release it to make Geralt enter the meditation position.
To build a campfire, press and hold the (MeditateWithCampfire) key and tap the (Meditate) key to have Geralt enter the meditation position and spawn a campfire. Once in the meditation state, you can tap the (Meditate) key again to enter the alchemy menu, or hold the (MoveTimeFoward) key to accelerate time while in meditation state. To exit the meditation state, simply press and hold the (ExitMedState) key.
}

Alchemy Menu

[Change Ingredients]

K/B&M
{Defaults: (IngredientChangeRequest = Right Mouse Button) (IngredientSelection Request = Left Mouse Button)

To change ingredients, select the ingredient to change with (Right Mouse Button) and a new menu will pop up with a list of ingredients that you currently have in your inventory. To select an ingredient, double click (Left Mouse Button).
}

Gamepad
{Defaults: (IngredientChangeRequest = Y/Triangle Button)

To change ingredients, select the ingredient to change with (Y/Triangle Button) and a new menu will pop up with a list of ingredients that you currently have in your inventory. To select an ingredient, press (Y/Triangle Button) or (A/Cross Button).
}

[Change Yield Quantity] (While this may be convenient, it's still a work in progress) - Version 1.2.2

K/B&M
{Defaults: (ModifierKeyPressed = Left Shift Button)

To change yield quantity, hold down (ModifierKeyPressed) and press the (Up or Down keys).
}

Gamepad
{Defaults: (ModifierKeyPressed = Right Trigger)

To change yield quantity, hold down (ModifierKeyPressed) and press (Up or Down on the digital pad).
}

[Shop Menu] (You can purchase ingredients directly in the alchemy shop menu)

K/B&M
{Defaults: (ModifierKeyPressed = Left Shift Button) (IngredientChangeRequest = Right Mouse Button)

To buy from the shop menu directly, hold down (ModifierKeyPressed) and select the ingredient that you wish to purchase with the (Right Mouse Button).
}

Gamepad
{Defaults: (ModifierKeyPressed = Right Trigger) (IngredientChangeRequest = Y/Triangle Button)

To buy from the shop menu directly, hold down (ModifierKeyPressed) and select the ingredient that you wish to purchase with the (Y/Triangle Button).
}

Ingredients:

Ingredients are comprised of six elemental substances: Aether, Rebis, Quebrith, Vitriol, Hydragenum or Vermilion. These substances are innate in all matter. Every alchemical concoction can be created by combining different ingredients containing these substances.
In vanilla, recipes were tied to specific ingredients, that is not the case anymore. You can replace any ingredient in a recipe for another that contains the same primary substance. This provides a great deal of flexibility when creating alchemical items, as you are no longer bound to any ingredient in particular.

Ingredients can contain specific secondary substances, Albedo, Rubedo, and Nigredo. These have no purpose on their own, but have useful side effects when used in a potion brewed with ingredients all containing the same substance:

• Albedo Dominance — Reduces toxicity of all subsequently consumed potions by 20%.

• Nigredo Dominance —  Increases damage inflicted by 20%.

• Rubedo Dominance — Accelerates vitality regeneration.

Bases:
All bases -solvents, catalysts and spirits - can be categorized as standard, high or top quality. If using a higher quality base versus a lower one, the required amount will be reduced to reflect this. The ingredients for potions, oils and bombs have been changed in order to better fit the new system.

Distillation:
When creating items, It is possible to use raw ingredients or to distill them to obtain the pure substance. Using the pure substance affords you the benefit of needing fewer measures to fulfill the ingredient requirements and, if using a strong or pure alcohol, allows you to create enhanced and superior versions of an item. Distilling ingredients will require the purest of alcohols and two empty bottles.

Potions, Oils and Bombs:

*Potions, bomb and oils no longer have a limit nor are treated as bundles. They stack in number and are removed when empty.
Oils are single use, each bottle can be applied to a blade once, and it's discarded.

*The duration of potions and mutagenic potions can be fully customized in the mod's menu.

Recipe Changes:

The superior recipes for oils, bombs and potions were eliminated. Creating higher tier items requires ingredients with higher concentration of primary substances or the raw substances themselves, in addition to high quality alcohol as a solvent. To create enhanced and superior versions of an item, the following rules have to be met:
  
Enhanced:

• Either all ingredients are concentrated (rich sources of a primary substance) and a high quality alcohol is used.
• The majority of ingredients(ingr / 2 + 1) are primary, concentrated or a combination of primary and concentrated, plus a top tier alcohol is used.

Superior:

• All ingredients are primary substances and a top tier alcohol is used.

Since the only way to obtain superior items is by using primary ingredients directly, it isn't possible to create superior potions with secondary substances, this is by design. Players will need to consider their options and determine whether it is best to go for the raw boost superior potions offer or the moderate boost of enhanced with the added utility of secondary substances.
If compromising is not an option, there is always the possibility of adding secondary substances to White Gull, but that incurs the penalties of additional toxicity and resources.

Additional Options:

• Modifying character requires fire source
• Weapon/armor sockets requires fire source
• Upgrading requires fire source
• Using dyes requires fire source
• Repairing weapon/armor requires fire source

Customization:
Pretty much every setting in the mod can be changed in the mod menu. Also refer to Mod Settings Descriptions.

Installation:

The Installation instructions are included inside the mod's root directory. Read them and follow them thoroughly, or use The Witcher 3 Mod Manager.

Vanilla Saved Games and Updaing Previous Versions Prior to Version 1.2.4:
Starting a new game is not required, however you may need to reset your skills, after Involved Alchemy Initialization, you will recieve a free Potion of Clarence, consume it and save the game (in a new slot recommended) and reload that same save.
Disclaimer: Involved Alchemy completely reworks the Alchemy system in The Witcher 3, removal of Involved Alchemy may not be possible when saved with Involved Alchemy installed, play-test the mod for a while and be sure it's what you want to finish the game with.

Compatibility:
Incompatible with any other alchemy overhaul. Scripts which aren't supposed to be merged have a 'Primer' header at the top. Do NOT try to merge them.
The XML files are indispensable for the mod's functionality. Make sure Involved Alchemy is properly merged or wins any conflicts.

Edits the following XML files:

{abilities and****abilities_pluseffects_potions.xml
}
{items and items_plusdef_item_alchemy_oils.xml
def_item_alchemy_potion.xml
def_item_alchemy_recipes_alcohol.xml
def_item_alchemy_recipes_mutagens.xml
def_item_alchemy_recipes_oils.xml
def_item_alchemy_recipes_petards.xml
def_item_alchemy_recipes_potions.xml
def_item_crafting_recipes.xml < Removed in Version 1.2.4
def_item_herbs.xml
def_item_ingredients.xml
def_loot_herbs.xml
}
{dlc\bob\data\gameplay\items****and items_plus
def_item_alchemy_recipes_dye.xml
def_item_alchemy_recipes_mutagens.xml
def_item_herbs.xml
def_item_ingredients.xml
def_loot_herbs.xml
}
Do NOT merge:

• AlchemyMenu.ws - The entire script was rewritten from scratch. Merging can not and will not work.
• AlchemyManager.ws - Many functions have been significantly changed here. A mod editing this script is most likely logically incompatible. Manual merging could be done, depending on the case, if the edited functions differ from those changed by Involved Alchemy.

If a mod you have changes one of these scripts, give priority to Involved Alchemy over the conflicting mod, or simply remove the conflicting scripts from that mod's folder.

~~Complementary Mods:
Improved Time Skip: Make effects persistent during meditation, fast travel tweaks and more~~

Special thanks to:

• All those that have bug tested the mod. :)

• weeketfull:For testing, specifically toxicity.

• Kezel:For testing, specifically quest potions.

• nter86: Used their SAVE FILE for testing.

• skyliner390: For the awesome mod ƤƦᎥოꂅᏒ, for this mod would not exist.

• CD Projekt: For this awesome game!