Volume 3

A comprehensive treatise on inorganic and theoretical chemistry / by J.W. Mellor.

  • Mellor, Joseph William, 1869-1938.
Date:
1947-1952
Catalogue details

Licence: In copyright

Credit: A comprehensive treatise on inorganic and theoretical chemistry / by J.W. Mellor. Source: Wellcome Collection.

    916/948 (page 900)
    found that, yellowish-green apatite from Malmberget became colourless after heat- ■ng to redness, and there was a small decrease in the index of refraction after the sample had been heated—the decrease was greater with the ordinary than with the extraordinary ray. The coloured varieties of apatite exhibit dichroism. H. Rosenbusch,ii and K. Zimanyi found that the extraordinary ray is more strongly absorbed than the ordinary ray even with colourless crystals. The latter found the ordinary and extra- ordinary rays to be respectively Ught yellow and bluish-green with pale green crystals ; reddish-yellow and bluish-green with bright green crystals; brownish- yellow and yellowish-green with yellow and brown crystals; and yellowish-brown and dark green with dark yellow crystals. A. K. Coomaraswamy found blue crystals of apatite from Ceylon to have sky-blue and pale wine-red colours respectively parallel and perpendicular to the c-axis; and P. Termier found the red crystals from Guillestre (Hautes-Alpes) to be orange or red when viewed along the a-axis, and pale yellow or white when viewed along the c-axis. A. Karnojitzky found crystals of apatite from Ehrenfriedersdorf to exhibit anomalous trichioism. C. Doelter noted thatcrystals of apatite are optically anomalous. H. Becquerel found the extraordinary ray absorption spectrum of a didymiferous apatite from Spain gave numerous lines —the most prominent corresponded with A=583; with the ordinary ray absorption spectrum, the lines A=582 and 575 are prominent. The colour of native apatite may be white, green, blue, red, yellow, grey, or brown. The colour of the mineral changes when heated—thus, K. Zimanyi 12 found greenish-yellow crystals from Malmberget became water-clear after heating to redness ; J. E. Wolff and C. Palache found the deep amethyst-coloured apatite from Minot became colourless when heated to about 320° ; P. Gaubert obtained a similar result with blue apatite from Priziac; and C. Doelter found the violet apatite from Auburn became paler when heated in chlorine at 500°, and colourless if heated to the same temp, in oxygen. F. Pupke attributed the colouring matter to the presence of manganese. E. von Kraatz-Koschlau and L. Wohler found up to 0'02 per cent, of carbon and O'OIl per cent, of hydrogen in coloured samples and attributed the coloration to the presence of organic matter ; but it must be remem- bered that many minerals have liquid and gaseous inclusions, and colourless minerals, in consequence, may furnish carbon dioxide and water, hence, the organic nature of the pigment has not yet been established. C. Doelter also showed that many colourless minerals are also coloured by exposure to cathode and other rays. Thus, violet-blue apatite from Auburn becomes paler and more violet by exposure to radium; ultra-violet rays darken the colour, cathode rays were without action. Colourless apatite from Pinzgan was changed to violet after 42 days’ exposure to radium ; and pale yellow apatite from Sulzbachtal was not changed. AH varieties of apatite so far examined are luminescent. Eupyrochroite and many phosphorites exhibit thermo-luminescence, and when heated, glow with a coloured light. E. Newbery and H. Lupton found that a sample of Canadian apatite which has been decolorized by heat, and recoloured brown in two days’ exposure to radium, emitted a strong violet thermo-luminescence many times stronger than the original unheated specimen. The brown colour disappeared rapidly in dayhght. K. Keilhack 12 found that many apatites glow with a yellow light when exposed to X-rays. He found the relative intensity of the light from green apatite from Ehrenfriedersdorf to be 34 ; that from a red apatite from the same locality, 43 ; that from yellow apatite from Tyrol, 18, and from Jumilla, 14 ; a water-clear apatite from Sulzbachtal, 30; from a Norwegian apatite, 21 ; and from a Canadian apatite, 20. A. Pochettino found no luminescence with X-rays, and with radium rays he found a feeble yeUowish-green luminescence the light of which was feebly polarized. C. Doelter found that the violet apatite from Auburn luminesced with a greenish-yellow light when exposed to the cathode rays, and pale yellow apatite from Sulzbachtal give a yellowish-green luminescence. L. Sohncke, and G. C. Schmidt have studied the yeUowish-green fluorescence of apatite. The