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New refractometers employing diamond and other minerals

Published online by Cambridge University Press:  14 March 2018

B. W. Anderson
Affiliation:
Laboratory of the Diamond, Pearl, and Precious Stone Trade Section of the London Chamber of Commerce
C. J. Payne
Affiliation:
Laboratory of the Diamond, Pearl, and Precious Stone Trade Section of the London Chamber of Commerce
J. Pike
Affiliation:
Messrs. Rayner & Keeler, Ltd., Instrument Makers, London

Extract

Direct-reading refractometers depend upon observation of the boundary between transmission and total internal reflection, when a flat surface of a specimen is placed in optical contact with the flat surface of the isotropic medium employed in the instrument. This medium is usually a heavy lead glass in the form of a hemisphere or prism. The upper limit to the range of indices which can be measured is determined by two factors: the refractive index of the medium employed in the instrument, and the refractive index of the liquid used to make optical contact between the two surfaces.

Liquids of high refractive index are essential to such instruments, and some reference to them may be conveniently made at this stage. Various pure liquids, mixtures, and melts of high refractivity have been proposed from time to time, chiefly as immersion media.

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 1940

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References

page 579 note 1 Anderson, B. W. and Payne, C. J., Nature, London, 1934, vol. 133, p. 66. [M.A. 5–503.]Google Scholar

page 579 note 2 Anderson, B. W. and Payne, C., loc. cit., and ibid., 1936, vol. 138, p. 168.Google Scholar

page 579 note 3 Merwin, H. E., Journ. Washington Acad. Sci., 1913, vol. 3, p. 35.Google Scholar

page 579 note 4 West, C. D., Amer. Min., 1936, vol 21, p. 245. [M.A. 6–460.]Google Scholar

page 580 note 1 Tully, B. J., Min. Mag., 1927, vol. 21, p. 324.CrossRefGoogle Scholar

page 581 note 1 Anderson, B. W. and Payne, C. J., Gemmologist, London, December 1937. [M.A. 7–131.]Google Scholar