In 1845 a further contribution to the study of allotropy was made by Anton Schrotter, who investigated the transformations of yellow and red phosphorus, phenomena previously noticed by Berzelius, the inventor of the term " allotropy."
The allotropy of selenium was first investigated by Berzelius; and more fully in 1851 by J.
The phenomenon of allotropy is not confined to the non-metals, for evidence has been advanced to show that allotropy is far commoner than hitherto supposed.
The allotropy of arsenic and antimony is also worthy of notice, but in the case of the first element the variation is essentially non-metallic, closely resembling that of phosphorus.
The term allotropy has also been applied to inorganic compounds, identical in composition, but assuming different crystallographic forms. Mercuric oxide, sulphide and iodide; arsenic trioxide; titanium dioxide and silicon dioxide may be cited as examples.
Osmond showed that the wonderful changes which thermal treatment andthe presence of certain foreign elements cause were due to allotropy, and from these and like teachings have come a rapid growth of the use of the so-called " alloy steels " in which, thanks to special composition and treatment, the iron exists in one or more of its remarkable allotropic states.
The allotropy of elements, we meet this increasing resistance with increasing valency.
Before leaving this phase of inorganic chemistry, we may mention other historical examples of allotropy.