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Name: Peter F.
Status: other
Age: 30s
Location: N/A
Country: N/A
Date: Saturday, May 18, 2002

Are there any other materials that are solid at room temperature besides Cryolite crystals that have the same refractive index (1.33) as water (transparent in water)?

Be aware that the index of refraction of a substance is a function of the wavelength of light used to measure it and the temperature. Usually the sodium 'D' doublet is used at 20 C. You will see such values tabulated as: nD20. In addition, for crystalline materials the index of refraction may depend upon the direction in which the index of refraction is measured. Also the index or refraction of a mixture of two liquids, one with an index greater than and the other less than 1.333 can be mixed (assuming they are miscible) to achieve a value of 1.333.

With those caveats, the index of refraction of: methanol is nD20= 1.3288, acetaldehyde is nD20= 1.3316, the mineral Valliaumite (a form of NaF) nD20= 1.33, and the mineral Hieralite (a form of K2SiF6) nD20= 1.34.

Vince Calder

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