dissociation (or ci as shi)

[Lat. di oci atio, from dis soc i at us, pa. par. of di ocio.] 1. Ord. Lang.: The act of disuniting, separating, or parting; the state of being disunited or broken up into parts. "As a consequence of the perfect action of di ociation in the lower layers." -Transit of Venus, in London Times . 2. Chem.: The partial decomposition of chemical compounds by the action of heat. ( Ro iter .)