Wax, microcrystalline

• USP–NFMicrocrystalline Wax

Amorphous wax; petroleum ceresin; petroleum wax (microcrystalline); E905

Refined mixture of solid, saturated aliphatic hydrocarbons obtained from petroleum · [63231-60-7]

Polymer, mixture or material of variable composition — no single molecular formula applies.

Semi-solid base, emollient

Typical concentrations: — · Dosage forms: Semi-solid

Used as a stiffening agent in creams and ointments, where it increases consistency and reduces 'sweating' of oils from petrolatum-based bases. It is also used in tablet and capsule coatings, in controlled-release matrices, in cosmetics and as a glazing and coating agent in foods.

Odourless, white to yellow or amber, waxy solid made of very small, irregular crystals. It is more flexible, tougher and more adhesive than paraffin wax and holds oils well.

Melting range

54–102 °C, depending on grade

Composition

mainly branched-chain and cyclic saturated hydrocarbons of higher molecular weight than paraffin wax

Solubility

soluble in chloroform, ether, volatile oils and most warm fixed oils; slightly soluble in ethanol; practically insoluble in water

Physical form

odourless, flexible, fine-crystalline wax; white to yellow or amber

Stable. Store in a well-closed container in a cool, dry place; avoid exposure to excessive heat.

Incompatible with strong oxidising agents.

Obtained from heavy petroleum fractions, such as the residues of lubricating-oil refining, by solvent de-oiling and crystallisation, followed by refining (for example hydrotreating or clay treatment) to remove impurities and colour.

Used in oral and topical products and foods and regarded as essentially non-toxic and non-irritant. Pharmaceutical and food grades must be highly refined to limit polycyclic aromatic hydrocarbons.

Observe normal precautions for the quantity handled. Take care with hot molten wax; it is combustible.

Accepted as a food additive in Europe (E905). Permitted as a petroleum wax in foods in the USA. Included in the FDA Inactive Ingredient Database (oral and topical preparations) and in non-parenteral medicines licensed in Europe.

Paraffin; petrolatum; white soft paraffin; wax, carnauba; wax, white.

Small additions of microcrystalline wax to paraffin wax or petrolatum improve flexibility and reduce brittleness and oil separation. The wide melting range means that the grade should be specified for each formulation.