The Physics
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Index of Refraction of Sodium Chloride (Table Salt)

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Bibliographic Entry Result
(w/surrounding text)
Faughn, Jerry S., Raymond A. Serway. College Physics, 6th Edition. Toronto: Brooks/Cole, 2003: 692.
Substance Index of Refraction
Sodium Chloride (NaCl) 1.544
(at 589 nm)
Indexes of Refraction, Microsoft Encarta Online Encyclopedia 2005.
Substance Index of Refraction
Sodium Chloride (Salt) 1.54
(at 590 nm)
Sodium Chloride: Refractive Index. Crystal Techno Ltd., Moscow. [see table below] 1.44–1.58
(16000 nm–350 nm)
Selby, Samuel, Robert C. Weast, Handbook of Chemistry and Physics 48th Edition, Cleveland: The Chemical Rubber Co., 1967-1968: B-280.
Physical Constants of Mineral
Name Formula Sp. gr. Hardness Crystalline form Index of Refraction (Na)
Halite NaCl 2.16–2.17 2.5 cub., wh., col., orange, red 1.544
Absolute Indices of Refraction, Reference Tables for Physical Setting/Physics, New York State Department of Education, 2002. Sodium Chloride 1.54 1.54
(at 589 nm)
Wavelength (µm) Refractive Index
0.35 1.58
0.46 1.56
0.68 1.54
1.25 1.53
7.30 1.51
10.6 1.49
12.0 1.48
13.1 1.47
14.2 1.46
15.1 1.45
16.0 1.44

Sodium chloride, also known as common salt, is one of the most important naturally occurring substances. It is composed of the elements sodium and chloride, and occurs naturally as the mineral halite through an ionic bond. It is found in the earth as well as our own bodies. Humans must maintain a certain concentration of salt to stay in equilibrium. Sodium (Na+) and chloride (Cl-) are the principal ions in the fluid outside of cells and they play a critical role in a number of life-sustaining processes.

From the beginning of civilization, humans have extracted sodium chloride from seawater and used it to their benefit. Salt is commonly used as a flavor enhancer and food preserver, since many microorganisms cannot survive in extremely salty conditions. Sodium chloride, when combined with water, is also used to de-ice roads and other surfaces. This compound is utilized in many applications, such as manufacturing paper, setting dyes in textiles and fabric, and producing soaps and detergents.

Sodium chloride also has an important application in optics and lasers, and therefore its index of refraction is an important value. The index of refraction for a particular medium is the speed of light in a vacuum divided by the speed of light in the medium. The amount of bending of a ray of light when it changes mediums depends on the change in the index of refraction between the two mediums. Sodium chloride has an approximate index of refraction if 1.54, which is relatively high compared to other solids. It is currently used in infrared optical windows, lenses and prisms.

Alina Genis -- 2005