  Gassendi's atomist accounts of chemical phenomena are equally ambitious, suggesting among other things how vapors are created and metals are soluble. Vapors are brought about by increases in the distance between atoms in a liquid volume. Heat atoms remove some of the atoms present in the volume, resulting in a greater percentage of void and the matter taking the form of vapors (O I 398b-399a). As concerns solubility, we account for aqua regia dissolving gold, and aqua fortis dissolving silver, as a result of their complementary atomic structures: gold atoms fit the pores of aqua regia and silver atoms fit the pores of aqua fortis (O II 33b ff, 39a-b).