I like the idea of the "Combine Potions with Alchemy level and Experimenter perk" mod, so I dare to improve his functionality. Now it's covering almost all pre-made potions and poisons in a game (excluding the Riften`s TG ones and "special" potions, like a "Ice Wraith Essence", "Esbern's Potion" etc., who don't have a ranks anyway). The list of possible combinations (in the cooking menu) is enormous big, so I decided to include some kind of "face-control" :) - now a recipe ("restore health" for example) will show up only if player actually have "restore health" potion(s) of any rank in the inventory. So player will see only the recipes, which can be maded right here and now (also which rank potions in this category is needed to reach the highest rank potion). Moreover, I added the check to "Concentrated poison" perk for the poisons combine (think it's obvious - if we want to concentrate poison, making a strong one from a several weak, we must have an appropriated perk). There is no such perk for the potions (in a "potions" sub-tree), but this is not big deal.
This modification is tested "in a fields", everything seems working for my hi-level char, who have access to many, many different vials, gathering through the long Skyrim journeys. Nevertheless, don't tested on a "fresh", new-born Dovahkin, so I don't completely sure it's bugs-free. Anyway, "there is no things in this universe which 100% compatible" ;)

So, what the purpose of this mod (speaking of the combining potions)? Here is a few answers, you can pick one of them, make your choice.
1. It's reduced the overall weight of yours 100500 flasks in the inventory (if they are not already weightless :))
2. Scrolling of the 100500 different flasks in the inventory is irritable, even in the SkyUI. Finding a needed one in this chaos is not an easy task. This mod help to reduce theirs overall quantity via combining.
3. In some mods flask-recovering of health/magica/stamina is not instant - it takes some time. In the heat of battle these several seconds can mean a difference between life and death. And if Dovahkin not drink the highest available potion at the moment, he may loose.

So combining pre-made potions/poisons come in handy. IMHO.

English and Russian version.
UPDATE: Now move them to "Optional" section. You can still use it, they are not outdated. But many of us use dozens of different mods, and criss-crossing of the same things lead (at least) to a conflicts and even to CTDs. So there is time to next move:
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COMBINE POTIONS-COMPATIBLE VERSION
I. For the compatibility reasons with other mods in this version the Distillation thing disabled, the Experimenter perk removed (//sigh), as well as the pre-requisite for Purity perk, bugged in vanilla. No perks messing at all.
Instead perk-related, this version doesn't modify the perk tree and gives you the ability to combine potions right of the bat. Of course, only if you learned Alchemy well and skill is high enough.

1. Most potions and poisons have a five ranks (1-weakest, 2-weak, 3-normal, 4-strong, 5-strongest).
So, apprentice alchemist (25) can mix two 1st rank vials into one 2nd rank vial.
Also he can mix one 1st rank vial and one 2nd rank vial into one 3rd rank vial.

Adept alchemist (50) can mix two 2nd rank vials into one 4th rank vial.
Also he can mix one 1st rank vial and one 3rd rank vial into one 4th rank vial.

Expert alchemist (75) can mix two 3rd rank vials into one 5th rank vial.
Also he can mix one 2nd rank vial and one 4th rank vial into one 5th rank vial.

2. If only four ranks present (for example, all "Fortify Skill..." and all "Resist..." potions), then:
Apprentice alchemist (25) can mix two 1st rank vials into one 2nd rank vial.

Adept alchemist (50) can mix one 1st rank vial and one 2nd rank vial into one 3rd rank vial.

Expert alchemist (75) can mix two 2nd rank vials into one 4th rank vial.
Also he can mix one 1st rank vial and one 3rd rank vial into 4th rank vial.

II. Shortly, if you see the recipe for combining in the cooking pot menu and have all appropriate vials, but the recipe still gray and unusable - leveling up your alchemy skill. There is only 3 recipe, required 100 Alchemy - this is Potion of Ultimate Healing/Magicka/Stamina, which restores all health/magic/stamina pts (combining two 5th rank appropriate vials).

III. In case of you still can't combine one or another vial, please, bugreport in the discussion thread.

IV. Warnings:
1. Use only ONE *.esp. The compatible version is not a patch, this is standalone mod.
2. This mod WILL conflict with "Combine Potions by Eldiran", and MAY conflict with other mod, which do the same things (currently I don't know any of such).
3. If you still decide to use an original version (with perks), keep in mind: BOSS may put this mod before Skyrim Redone (SkyRe) or another altering-alchemy-tree mod. Depending on loading order the alchemy perks for distillation are overwritten and all functionality of my mod is gone to Oblivion. So, use yours favorite Skyrim mod manager (native SkyrimLauncher, WryeBash, NexusModManager or brilliance Mod Organizer - the choice is yours) and manually drag this mod AFTER Skyrim Redone (or other mods, who dealing with perks in Alchemy tree).

V. There is no need to translate a compatible version to Russian or other language, without perks he is completely language-independent.
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The full list of vanilla potions (covering by this mod) is here,
http://elderscrolls.wikia.com/wiki/Potions_(Skyrim);
and http://elderscrolls.wikia.com/wiki/Poison_(Skyrim) for poisons.
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Author's permission is received.
....And the credits goes to Savagemoonlight for the original idea and his mod!
Also, appreciate the Eldiran, who was the first in this field
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p.s. Now the link to original mod is dead (R.I.P.), so my one is something like his successor.
In memory of the ancestor I upload the original readme (with my comments), this must explain the mod's mechanic more than I did :)