Monographs: Pharmaceutical substances: Adeps solidus - Hard fat

Chemical name. Hard fat.

Description. A white, brittle, unctuous mass; almost odourless.

Solubility. Practically insoluble in water; freely soluble in ether R; slightly soluble in ethanol (~750 g/l) TS.

Category. Suppository base.

Storage. Hard fat should be kept in a well-closed container, protected from light, and stored at a temperature not exceeding 5 °C below the melting range.

Additional information. On warming, hard fat melts to a colourless to slightly yellow liquid. On shaking the molten material with an equal quantity of hot water, forms a white emulsion.

Note: For certain applications, it may be necessary to comply with more restrictive specifications.

Requirements

Definition. Hard fat is a mixture of mono-, di- and triglyceride esters of higher saturated fatty acids (C₁₀H₂₀O₂ to C₁₈H₃₆O₂).

Melting range. Cool the charged tube at a temperature below 10 °C for 24 hours; 33-40 °C.

Acid value. Not more than 0.5.

Hydroxyl value. Not more than 50.

Iodine value. Not more than 3.

Peroxide value. Not more than 6.

Saponification value. Use 2.0 g; 220-250.

Unsaponifiable matter. Use 5 g; not more than 1.0%.

Ash. Not more than 0.5 mg/g.

Alkaline impurities. Dissolve 2 g in a mixture of 1.5 ml of ethanol (~750 g/l) TS and 3 ml of ether R. Add 0.05 ml of bromophenol blue/ethanol TS; not more than 0.15 ml of hydrochloric acid (0.01 mol/l) VS is required to change the colour of the solution to yellow.

Decomposition products. Shake 1 g with 1 ml of hydrochloric acid (~420 g/l) TS for 1 minute, add 1 ml of resorcinol/toluene TS, shake for 5 seconds, and allow to stand for 5 minutes; the aqueous layer is not more intensely coloured than 1 ml of a mixture of 0.4 ml of potassium permanganate (0.002 mol/l) VS and 9.6 ml of water.