Tables for
Volume C
Mathematical, physical and chemical tables
Edited by E. Prince

International Tables for Crystallography (2006). Vol. C, ch. 3.3, pp. 160-161

Section 3.3.3. High-index media

E. S. Larsen Jr,a R. Meyrowitzb and A. J. C. Wilsonc

aUS Geological Survey, Washington 25, DC, and Harvard University, Cambridge, MA, USA,bUS Geological Survey, Washington 25, DC, USA, and cSt John's College, Cambridge, CB2 1TP, England

3.3.3. High-index media

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Refractive indices greater than 2.1 present special difficulties. Merwin & Larsen (1912[link]) used melts of sulfur and selenium, satisfactory up to index 2.72. Mixtures of selenium and As2Se3 can be used up to index 3.17 (Larsen & Berman, 1934[link]). Above about 2.2, the index must be determined at a wavelength for which selenium is transparent; the red line of lithium is convenient.


Larsen, E. S. Jr & Berman, H. (1934). The microscopic determination of nonopaque minerals, 2nd ed. US Geol. Survey Bull. No. 848.
Merwin, H. E. & Larsen, E. S. Jr (1912). Mixtures of amorphous sulphur and selenium as immersion media for the determination of high refractive indices with the microscope. Am. J. Sci. 34, 42–47.

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