The New Student's Reference Work/Allotropy
Allotropy (ăl-lŏt-rō' pŷ) or Allotropism, a chemical term to explain a conversion or change in physical property, but not in substance, in certain bodies. More explicitly, it is the property or capability which certain bodies show of assuming different forms and qualities under a presumed diversity of molecular arrangement. Examples of allotropic conditions are seen in carbon, sulphur, phosphorus and oxygen; practical instances are carbon (1) in its soft state, as in plumbago, black lead and charcoal and (2) (hard and crystallized) as in the diamond. Phosphorus is another instance of this dual property: (1) as a colorless wax-like solid, poisonous and dangerously inflammable and (2) as a red powder with neither of these destructive qualities. Similar contrasts are seen in oxygen and ozone.