Synthetic Paraffin
» 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, using a suitable synthetic isoparaffinic petroleum hydrocarbon solvent. It may contain not more than 0.005 percent of a suitable antioxidant.
Packaging and storage— Preserve in well-closed containers.
Labeling— The labeling indicates its congealing temperature, viscosity, and needle penetration range under specified conditions.
Identification— Infrared Absorption 197—A thin film of it, cast from a melt onto a cesium bromide plate, exhibits a pair of very strong IR absorption peaks between 2840 cm1 and 3000 cm1, a pair of moderately strong peaks between 1430 cm1 and 1490 cm1, a pair of medium peaks between 720 cm1 and 750 cm1, and only weak peaks at any other wave numbers.
Absorptivity (see Spectrophotometry and Light-scattering 851)— Transfer 50 to 100 mg, accurately weighed, to a 100-mL volumetric flask. Dissolve in decahydronaphthalene at 88, dilute with the same solvent at this temperature to volume, and mix. Using the same solvent in a matched cell as the blank, determine the absorbance of the solution in a 10-cm jacketed cell at 290 nm, with a suitable spectrophotometer, both cells being maintained at 88. Calculate the absorptivity: it is not greater than 0.01.
Oil content: not greater than 0.5%, as determined by following ASTM Method D721-68, “Standard Test Method for Oil Content of Petroleum Waxes” (Reapproved 1987).*

*  Available from the American Society for Testing and Materials, 1916 Race St., Philadelphia, PA19103.
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Topic/Question Contact Expert Committee
Monograph Hong Wang, Ph.D.
(EM205) Excipient Monographs 2
USP32–NF27 Page 1296