I'm ready to start up an Xcrawl Campaign, it has some spells specific to it so I need to figure out whether to allow specific spells onto the alchemist list. I need criteria on what constitutes an alchemist extract, anybody have this?
Not as such, but generally alchemist extracts are spells which affect the body of the caster only, Some are more general spells which can be restricted in that way. A few create physical effects from the body of the caster like vomit swarm.
Generally they must have a target of "Personal" or "Touch".
Also Alchemists can't make extracts that have a "Focus" component, although they ignore "Divine Focus" components.
Note: Both of these rules are broken by specific extracts on the existing Alchemist firmulae list. This is because Alchemist's can use wands/staves of any spell that appears on their Formulae list without a UMD check. Thus an Alchemist could use a wand of those spells even though they cannot be made into Extracts. This was a deliberate choice by Paizo.