Mineral Oil — Frequently Asked Questions

The degree of refining, and it is a safety distinction rather than a grade preference. Lightly refined mineral oil contains polycyclic aromatic hydrocarbons, some of which are carcinogenic, and is classified accordingly. White oil is hydrotreated until those aromatics are effectively eliminated and is tested against pharmacopoeial limits including the ultraviolet absorbance test.

Residual polycyclic aromatic hydrocarbons. Those compounds absorb strongly in the ultraviolet, so measuring absorbance of a solvent extract against a pharmacopoeial limit provides a sensitive check that refining has removed them. Only material passing that test may be used in laxatives, baby oil, food-contact lubricants and cosmetics.

They are closely related but specified against different monographs, and the applicable standard differs by jurisdiction. Both require the aromatic content to be controlled to pharmacopoeial limits. The intended contact and the destination market should be stated at enquiry so the correct grade and compliance documentation are supplied.

Primarily by viscosity, which determines film thickness, spreading and feel, together with pour point where low-temperature performance matters and colour where appearance does. For cosmetic use, viscosity largely determines whether the material reads as light or heavy on the skin, so it is chosen against the sensory target as much as the technical one.