The simple approach is to make a KBr pellet. A few milligrams of sample is ground with about 1 gram of KBr solid. This sample is then places in a metal die and is pressed to form a pellet. The IR of the pellet is recorded. It's worth taking a brief detour to discuss why a KBr pellet works.
Most salts appear white because they reflect and scatter light.
Even a thin layer of powder stops all light and would appear opaque. Each tiny crystal is probably completely transparent. After light has encountered a few time crystals, most has been multiply reflected and very little is transmitted directly through the sample. When we form a KBr pellet, we replace the air with crystalline KBr which has a refractive index quite close to that of our samples. This, only a small fraction of light is reflected and the rest is transmitted.