Purified Calling states that upon casting the spell, you must immediately begin the ritual for Summoning your Eidelon. But what if you have Summon Eidelon in your repertoire? Do you really have to take the full minute after PC, or is it written that way because 2 Standard Actions to fully heal the beast is percieved as game breaking?
And if it is, why have Purified Calling at all? It just means that your magical pet Hercules will be healed between encounters instead of in the middle of them.
Not sure I entirely understand your questions.. but I'll give it a shot.
I wish PC was written slightly differently. It should spell out explicitly that you have to cast the spell when your Big E isn't summoned. One sentence to that effect, I think, would clarify it nicely.
Instead you are left thinking you can just cast it on your Big E and that it works like a "Heal" spell except..
It clearly has the limitation that you MUST SUMMON it right after you cast the spell and that upon being summoned it is healed/cleansed.
Could it be worded better? Absolutely.. but I think even as is, you have to conclude that your Big E isn't there when you cast Purified Calling and that it cleanses/heals it, then you summon it and it appears whole and hale.
You can't use it in the middle of a fight unless you want to spend the time in mid fight to summon him out.
Now- as to whether or not the spell works with Summon Eidolon.. it doesn't seem to.
Its clear and unfortunately firm that you have to begin the ritual, not cast another spell.
Obviously though, just my .02 on the matter.
-S