|Janis "The Gentleman" Scarnetti|
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. (Personally I think this is just confusing and it'd be easier to just let them make those spells into extracts, but whatever.)