Pseudopolymorphism

 The term pseudo means false. Phenomenon in which solvent molecules get incorporated into crystal lattice of solid are known as solvates. This solvates exist in different crystal form called pseuopolymorphs and the phenomenon is called as pseudopolymorphism.Also known as hydrates when water is solvent. E.g. when the potent synthetic estrogen ‘ethynylestradiol’ is crystallized from the solvents acetonitrile, methanol, chloroform and saturated with water four different crystalline solvates are formed.

How to differentiate pseudopolymorphs from true polymorphs?

Pseudopolymorphs can be differentiated from true polymorphs by observing melting behavior in silicon oil using hot stage microscopy. Here in this technique psrudopolymorphs evolve gas(steam or solvent vapors)causing bubbling of the oil. While true polymorphs merely melts, forming second globular phase.