Herapathite

Herapathite, or iodoquinine sulfate, is a chemical compound whose crystals are dichroic and thus can be used for polarizing light. The composition of herapathite has been shown by the Danish chemist Sophus Mads Jørgensen in 1877 and others to be 4QH2·3SO4·2I3·6H2O, where Q denotes the quinine molecule C20H24N2O2. The crystal can give up at least some of its water without losing its form and optical properties.[1]

Herapathite
Names
IUPAC name
(R)-[(2S,4S,5R)-5-ethenyl-1-azabicyclo[2.2.2]octan-2-yl]-(6-methoxyquinolin-4-yl)methanol;sulfuric acid;tetratriiodide
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.028.677
EC Number
  • 231-544-9
UNII
Properties
C60H84I12N6O30S6
Molar mass 3084.56 g·mol−1
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

According to Edwin H. Land, it was discovered in 1852[2] by William Bird Herapath, a Bristol surgeon and chemist. One of his pupils found that adding iodine to the urine of a dog that had been fed quinine produced unusual green crystals. Herapath noticed while studying the crystals under a microscope that they appeared to polarize light.[3]

In the 1930s, Prof. Ferdinand Bernauer invented a process to grow single herapathite crystals large enough to be sandwiched between two sheets of glass to create a polarizing filter; these were sold under the Bernotar name by Carl Zeiss. Herapathite can be formed by precipitation by dissolving quinine sulphate in acetic acid and adding iodine tincture.[4]

Herapathite's dichroic properties came to the attention of Sir David Brewster, and were later used by Land in 1929 to construct the first type of Polaroid sheet polarizer. He did this by embedding herapathite crystals in a polymer instead of growing a single large crystal.

Production

 
Iodosulfate of Quinine Crystals—The beautiful crystallisation for the polariscope may be prepareed (Microscop) as follows. Mix 3 drams of pure acetic acid with 1 dram of alcohol; add to these 6 drops of diluted (1:9) sulfuric acid. One drop of this fluid is to be placed on a glass slide and the merest atom of quinine added. time given for solution to take place; then upon the a very fine glass rod a very minute drop of tincture of iodin(sic) is to be added. After a time the polarizing crystals of iodosulfate of quinine are slowly produced without the aid of heat[5]

See Also
  • Bernauer, F. (1935). "Neue Wege zur Herstellung von Polarisatoren". Forschritte der Mineralogie, Kristallographie und Petrographie Neunzehnter Band
  • Land, E.H. (1951). "Some aspects on the development of sheet polarizers". Journal of the Optical Society of America. 41 (12): 957–963. doi:10.1364/josa.41.000957.
  • Marks, A. M. (1969). "Electrooptical Characteristics of Dipole Suspensions". Applied Optics. 8 (7): 1397–1412. Bibcode:1969ApOpt...8.1397M. doi:10.1364/AO.8.001397.

References
  1. West, C.D. (c. 1936). "Crystallography of Herapathite" (PDF). The American Mineralogist: 731. Retrieved 19 March 2015.
  2. W. B. Herapath (1852). "XXVI. On the optical properties of a newly-discovered salt of quinine, which crystalline substance possesses the power of polarizing a ray of light, like tourmaline, and at certain angles of rotation of depolarizing it, like selenite". Phil. Mag. London: Taylor & Francis. 3 (17): 161–173. doi:10.1080/14786445208646983.
  3. Kahr, Bart; Freudenthal, John; Phillips, Shane; Kaminsky, Werner (2009). "Herapathite". Science. 324 (5933): 1407. Bibcode:2009Sci...324.1407K. doi:10.1126/science.1173605. PMID 19520951.
  4. Gabba, Luigi (1884). Trattato Elementare di Chimica Inorganica ed Organica [Elementary Treatise on Inorganic and Organic Chemistry] (in Italian). Francesco Vallardi. p. 516.
  5. "Laboratory Notes: Iodosulfate of Quinine Crystals". Western Druggist. 19 (9): 418. 1897.
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