- Identity
- IR spectrum matched to a reference, as in the NF monograph.
- Viscosity
- Kinematic viscosity at 25 °C against the nominal grade, the main lot-acceptance test.
- Volatile content
- Loss on heating, which shows residual low-molecular-weight siloxanes.
- Cyclic siloxane content (D4, D5, D6)
- GC for residual cyclic siloxanes, which some markets restrict in finished cosmetics.
- Refractive index and specific gravity
- Physical constants that confirm identity and grade.
- Heavy metals
- Lead, arsenic and other elements by ICP-MS or ICP-OES against the supplier's specification or the applicable USP, FCC or cosmetic-grade limit.