A student is doing a lab and measures the speed of light to be $2\mathrm{.}21{10}^8\frac{m}{s}$ as it ${?}^{t^8}$ travels through a certain substance. Use the table below to determine the identity of the substance.

INDEX OF REFRACTION FOR DIFFERENT MEDIA

$\backslash$table$[[$Medium$,$Index of Refraction$],[$Vacuum$,1\mathrm{.}00],[$Air$,1\mathrm{.}00],[$Water$,1\mathrm{.}33],[$Ethanol$,1\mathrm{.}36],[$Glycerin$,1\mathrm{.}47],[$Quartz$,1\mathrm{.}54],[$Diamond$,2\mathrm{.}42]]$