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

International Tables for Crystallography (2006). Vol. C, ch. 3.3, p. 160

Section 3.3.2. Media for general use

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

3.3.2. Media for general use

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The immersion media listed in Table 3.3.2.1[link] are easily prepared, stable, and generally satisfactory. They were selected because they require only a small number of liquids for their preparation. In general, each liquid is miscible in the liquids with higher and lower indices of refraction so that any intermediate mixture can be easily prepared.

Table 3.3.2.1| top | pdf |
Immersion media for general use in the measurement of index of refraction

Note: Further lists are given by Hartshorne & Stuart (1960[link]).

 [n^{20^\circ\rm C}_{D}]Temperature coefficient (dn/dT)Dispersion
Water 1.333 1 × 10−4 Slight
Glycerol 1.473 2.2 × 10−4 Slight
n-Octane 1.400 4.8 × 10−4
n-Hexadecane 1.434 3.8 × 10−4 Slight
Kerosene (Paraffin) 1.448 3.5 × 10−4 Slight
Petroleum oil (Nujol) 1.477 4 × 10−4 Slight
α-Chloronaphthalene 1.626 4 × 10−4 Moderate
Methylene iodide 1.740 6.4 × 10−4 Rather strong
Methylene iodide saturated with sulfur 1.778 6 × 10−4 Rather strong
AsBr3 plus 10% sulfur (mix with methylene iodide or α-bromonaphthalene for lower n) 1.814 (25° C) 7 × 10−4 Rather strong
2S, 2As2S2, 6AsBr3 (mix with 10% sulfur in AsBr3 for lower n) 2.003 (25° C) 6 × 10−4 Rather strong
2Se, 2As2S2, 6AsBr3 (mix with 10% sulfur in AsBr3 for lower n) 2.11 (25° C) 6 × 10−4 Rather strong

The liquids up to n = 1.770 are measured on an Abbe refractometer; those with higher values for n are measured in a hollow glass prism prepared from selected object glasses and mounted on a goniometer or on a spectrometer (Butler, 1933[link]; Larsen & Berman, 1934[link], pp. 18–20).

A set of immersion liquids with indices of refraction differing by one unit in the second decimal place (1.510, 1.520, 1.530, [\ldots]) is used for routine work. The liquids are best kept in 15 ml dropping bottles with plastic caps and glass dropping rods. These bottles are more satisfactory than the more expensive dropping bottles with solid glass stoppers and ground-glass caps because there is less trouble with the stopper cementing to the bottle. The bottle should be about half full.

Some crystals dissolve rapidly in the liquids tested. A measurement can usually be made by performing the reading rapidly. If the crystal and the liquid have nearly the same indices of refraction, the index of the liquid is not much changed by the solution of the crystal.

References

Butler, R. D. (1933). Immersion liquids of intermediate refraction. Am. Mineral. 18, 386–401.
Hartshorne, N. H. & Stuart, A. (1960). Crystals and the polarising microscope, 3rd ed. London: Arnold.
Larsen, E. S. Jr & Berman, H. (1934). The microscopic determination of nonopaque minerals, 2nd ed. US Geol. Survey Bull. No. 848.








































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