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.
Chemie, 24, p. 468) submitted the view that fluorescence was due to the presence of certain " fluorophore " groups; such groupings are the pyrone ring and its congeners, the central rings in anthracene and acridine derivatives, and the paradiazine ring in safranines.
This oscillation may be represented in the case of acridine and fluorescein as This theory brings the property of fluorescence into relation with that of colour; the forms which cause fluorescence being the coloured modifications: ortho-quinonoid in the case of acridine, paraquinonoid in the case of fluorescein.
This theory explains the fluorescence of anthranilic acid (o-aminobenzoic acid), by regarding the aniline residue as the luminophore, and the carboxyl group as the fluorogen, since, apparently, the introduction of the latter into the non-fluorescent aniline molecule involves the production of a fluorescent substance.
Although the theories of Meyer and Hewitt do not explain (in their present form) the behaviour of anthranilic acid, yet Hewitt has shown that his theory goes far to explain the fluorescence of substances in which a double symmetrical tautomerism is possible.
Acridine crystallizes in needles which melt at 110° C. It is characterized by its irritating action on the skin, and by the blue fluorescence shown by solutions of its salts.
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.
On heating it melts at 95.6° (Bunsen) to a liquid resembling mercury, and boils at 877.5° (Ruff and Johannsen, Ber., 1905, 38, p. 3601), yielding a vapour, colourless in thin layers but a peculiar purple, with a greenish fluorescence, when viewed through thick layers.
Fluorescence and Phosphorescence.
It is not possible here to enter into a detailed description of the phenomena of fluorescence (q.v.), though their importance from a spectroscopic point of view has been materially increased through the recent researches of Wood s on the fluorescence of sodium vapour.
Showed that the vibrating system of the fluorescent light seems identical with that observed by absorption in the fluted band spectrum, Wood excited the fluorescence by homogeneous radiation and discovered some remarkable facts.
It crystallizes in colourless plates, possessing a violet fluorescence, melting at 112-113° and boiling at 293-295° C. By oxidation with chromic acid in glacial acetic acid solution, it is converted into diphenylene ketone (C8H4)2 CO; whilst on heating with hydriodic acid and phosphorus to 250-260° C. it gives a hydro derivative of composition C13H22.
He concluded that the gases are due to the decomposition of an organic colouring matter, which has, however, no connexion with the fluorescence or thermo-luminescence of the mineral.
The fluorescence is visible in an acid solution containing I part in 200,000 of water.
The other alkaloids are distinguished from quinine thus: quinidine resembles quinine, but is dextro-rotatory, and the iodide is very insoluble in water; the solution of cinchonidine, which is laevo-rotatory, does not give the thalleoquin test, nor fluorescence; cinchonine resembles cinchonidine in these respects, but is dextrorotatory.