How does the Purity Perk determine whether you are making a Potion or a Poison? Does it ask you which you want or does it randomly determine whether it's the negative or positive effects that will be eliminated?

Thanks.

think it's the first effect that determines it but not sure

I never used purity perk because it reduces the price of the 3 ingredient potions I create that I make to sell.

Since I haven't used the purity perk, this is my educated guess based on my experience of making many potions but not using purity perk. Each potion that you create is either a potion or a poison. If the potion that you create is named potion, then all negative effects are removed. If your potion is named poison, all positive effects are removed. Most expensive effect determines what type of potion it's going to be.

[Edited for accuracy]

Well ... what effects which effect is first then? I have noted that potions with multiple effects are sometimes listed as potions, even though there is a poison aspect to them. But I have no idea how which is listed first is determined.

I think the overall potion's effect is based on the cumulative ingredients effects. As in using two ingredients that give Health Restore would make a Restore Health Potion and Purity would remove any poison effects in this case. I don't know if the first one has any more weight, as you can't make a potion from one ingredient. I would imagine the first effect has precedence over any other effects. You may also have to have the negative effect show up twice in the ingredients for it to be added to any positive effect potion. Or, vice versa.

I think any potions that would throw this off, as in two Restore and two Poison ingredients would just result in a failed potion.

This can be used to experiment with ingredients to see what takes precedence when there are multiple effects, and multiple counter effects.

http://skyrim.melian.cc/?cmd=cmdSkyrimAlchemyWizard

Can you change the order that you load the ingrediants? For example if you keep getting the Potion, but you want the Poison, can you reverse the order you select them and get the Poison?

Honestly I'm beginning to wonder if the Purity Perk is even something you would want to have. Not worried about the money since I'll have more than I can ever spend by the time I get any skill to 100.

Try the lab that I linked you to, it creates potions just like the Alchemy table does.

I just tried a quick experiment with blue mountain flower, bear claws, and wheat. This combination has 3 effects: restore health, fortify health and damage magicka regen. The name of the potion always comes out as Poison of Damage Magicka Regen no matter what order I use the ingredients. So it seems to me now that the most expensive effect determines the name of the potion and the outcome of the Purity effect.

Are each of these effects the first listed on the ingredient?

Does it change if you add two ingredients that have Restore Health that cost less than the ingredient with Damage Magicka?

I would have thought whichever Effect "heading" you selected would determine if it were potion or a poision...I guess not.

Is there a list somewhere of the base cost of potion/poison effects?

It might not work off of base. There are perks that increase the magnitude of poison/potion effects, thus increaseing said effects relative value.