Edition: BP 2025 (Ph. Eur. 11.6 update)
Liquid Paraffin and Magnesium Hydroxide Oral Emulsion General Notices
DEFINITION
Liquid Paraffin and Magnesium Hydroxide Oral Emulsion is a 25% v/v dispersion of Liquid Paraffin in an aqueous suspension containing 6% w/w of hydrated magnesium oxide prepared from a suitable grade of Light Magnesium Oxide.
The oral emulsion complies with the requirements stated under Oral Liquids and with the following requirements.
Content of magnesium hydroxide, Mg(OH)2
5.1 to 7.0% w/w.
Content of liquid paraffin
19.7 to 24.0% w/w.
ASSAY
For magnesium hydroxide
Dilute 4 g with 50 mL of water, shake with 25 mL of 0.5M hydrochloric acid VS and titrate with 0.5M sodium hydroxide VS using methyl orange solution as indicator. Each mL of 0.5M hydrochloric acid VS is equivalent to 14.58 mg of Mg(OH)2.
For liquid paraffin
Extract the neutralised liquid obtained in the Assay for magnesium hydroxide with three 25 mL quantities of a mixture of equal volumes of petroleum spirit (boiling range, 40° to 60°) and ether, wash the combined extracts with two 10-mL quantities of water, discard the washings, evaporate the solvent, add 5 mL of acetone and again evaporate. Repeat the addition and evaporation of acetone until the residue is free from water, dry at 105° for 15 minutes and weigh.
