It is remarkable for its fluorescence, which in the opinion of some authorities adds to its beauty.
Fluorescence and Constitution.-The physical investigation of the phenomenon named fluorescence-the property of transforming incident light into light of different refrangibilityis treated in the article Fluorescence.
The fluorescence is visible in an acid solution containing I part in 200,000 of water.
When freshly prepared it dissolves in cold water to form an indigocoloured solution with a brownish fluorescence of colloidal aurous oxide; it is insoluble in hot water.
Its solution in concentrated sulphuric acid is of a yellow colour and shows a marked blue fluorescence.