# Refractive index of barium sulfate

What is the refractive index of barium respectively where do I find it? I only find values for alpha, beta and x-ray radiation like on https://pubchem.ncbi.nlm.nih.gov/compound/barium_sulfate#section=Decomposition

I need it for all wavelengths or at least at 455 nm. Thank you in advance!

The index of refraction of $\ce{BaSO4}$ at 589 nm can be found in "Index of Refraction of Inorganic Crystals", in CRC Handbook of Chemistry and Physics, 90th Edition (CD-ROM Version 2010), David R. Lide, ed., CRC Press/Taylor and Francis, Boca Raton, FL.

Separate values are given for the indexes of the orthorhombic crystals:

\begin{align} n_x &= 1.6362\\ n_y &= 1.6374\\ n_z &= 1.6480 \end{align}

• At first thanks a lot! Unfortunately this is at another wavelength and there might be a (huge) difference due to the wavelength. Are anywhere some databases about materials and their properties which are common to look at?
– Ben
Aug 18, 2017 at 6:54
• Have a look for the Sellmeier equations, this will give you an indication of how the refractive index varies with wavelength. You may then have to 'guestimate' a value but it will probably not be so much in error . Aug 18, 2017 at 13:34
• @porphyrin Maybe I was too fast: How do I estimate it with the help of the Sellmeier equation? I only have the wavelength and B and C are missing(?)
– Ben
Aug 21, 2017 at 11:21
• well, you know that as your wavelength is shorter than wavelength used in std tables (Na D line) so refractive index will be larger. (a) choose two materials with similar refractive index one above and one below whose params are known and interpolate. (b) if (a) is not possible, as curves are all similar shape take one for, say, quartz or some glass etc and set value at Na D line to your value for BaSO4 and then work out refractive index at your wavelength. Aug 21, 2017 at 11:47
• continued ... Try this with different solids and average, probably wont be so far in error. If you could make a crystal prism out of BaSO4 then you measure directly. (If you have access to fast lasers or time correlated single photon counting you could measure delay time through crystal directly). Aug 21, 2017 at 11:47