Name: Paraffin
CAS No: Paraffin [8002-74-2]
BP: Hard Paraffin JP: Paraffin PhEur: Paraffin, Hard USP-NF: Paraffin
Hard wax; paraffinum durum; paraffinum solidum; paraffin wax.
Paraffin [8002-74-2]
Paraffin is a purified mixture of solid saturated hydrocarbons having the general formula CnH2nþ2, and is obtained from petroleum or shale oil.
Paraffin is mainly used in topical pharmaceutical formulations as a component of creams and ointments. In ointments, it may be used to increase the melting point of a formulation or to add stiffness. Paraffin is additionally used as a coating agent for capsules and tablets, and is used in some food applications. Paraffin coatings can also be used to affect the release of drug from ion-exchange resin beads.(1)
Paraffin is an odorless and tasteless, translucent, colorless, or white solid. It feels slightly greasy to the touch and may show a brittle fracture. Microscopically, it is a mixture of bundles of microcrystals. Paraffin burns with a luminous, sooty flame. When melted, paraffin is essentially without fluorescence in daylight; a slight odor may be apparent.
See Table I.
Density 0.84–0.89 g/cm3 at 208C Melting point Various grades with different specified melting ranges are commercially available. NIR spectra see Figure 1. Solubility Soluble in chloroform, ether, volatile oils, and most warm fixed oils; slightly soluble in ethanol; practically insoluble in acetone, ethanol (95%), and water. Paraffin can be mixed with most waxes if melted and cooled.
Paraffin is stable, although repeated melting and congealing may alter its physical properties. Paraffin should be stored at a temperature not exceeding 408C in a well-closed container.
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Paraffin is manufactured by the distillation of crude petroleum or shale oil, followed by purification by acid treatment and filtration. Paraffins with different properties may be produced by controlling the distillation and subsequent congealing conditions. Synthetic paraffin, synthesized from carbon monoxide and hydrogen is also available;
Paraffin is generally regarded as an essentially nontoxic and nonirritant material when used in topical ointments and as a coating agent for tablets and capsules. However, granulomatous reactions (paraffinomas) may occur following injection of paraffin into tissue for cosmetic purposes or to relieve pain. Long-term inhalation of aerosolized paraffin may lead to interstitial pulmonary disease. Ingestion of a substantial amount of white soft paraffin has led to intestinal obstruction in one instance.(2–6)
Observe normal precautions appropriate to the circumstances and quantity of material handled. In the UK, the recommended workplace exposure limits for paraffin wax fumes are 2 mg/m3 long-term (8-hour TWA) and 6 mg/m3 short-term.(7)
Accepted in the UK for use in certain food applications. Included in the FDA Inactive Ingredients Database (oral capsules and tablets, topical emulsions, and ointments). Included in nonparenteral medicines licensed in the UK. Included in the Canadian List of Acceptable Non-medicinal Ingredients.
Light mineral oil; microcrystalline wax; petrolatum; synthetic paraffin. Synthetic paraffin Molecular weight 400–1400 Appearance A hard, odorless, white wax consisting of a mixture of mostly long-chain, unbranched, saturated hydrocarbons along with a small amount of branched hydrocarbons. Melting point 96–1058C Viscosity (dynamic) 5–15 mPa s (5–15 cP) at 1358C. Comments The USP32–NF27 states that synthetic paraffin is synthesized by the Fischer–Tropsch process from carbon monoxide and hydrogen, which are catalytically converted to a mixture of paraffin hydrocarbons. The lower molecular weight fractions are removed by distillation and the residue is hydrogenated and further treated by percolation through activated charcoal. This mixture may be fractionated into its components by a solvent-separation method. Synthetic paraffin may contain not more than 0.005% w/w of a suitable antioxidant.
The more highly purified waxes are used in preference to paraffin in many applications because of their specifically controlled physical properties such as hardness, malleability, and melting range. A specification for synthetic paraffin is contained in the Food Chemicals Codex (FCC).(8) The EINECS numbers for paraffin are 232-315-6 and 265-154-5.