The Collaborative International Dictionary of English v.0.48:

Vaporizable \Vap"o*ri`za*ble\ (v[a^]p"[-o]*r[imac]`z[.a]*b'l or
   v[=a]"p[~e]r*[imac]`z[.a]*b'l; 110), a.
   Capable of being vaporized, or converted into vapor.
   [1913 Webster]

WordNet (r) 3.0 (2006):

vaporizable
    adj 1: (used of substances) capable of being volatilized [syn:
           evaporable, vaporific, vapourific, vaporizable,
           vapourisable, volatilizable, volatilisable]