Zinc and Castor Oil Creamb
DEFINITION
| Zinc Oxide, finely sifted | 75 g |
| Virgin Castor Oil | 500 g |
| Cetostearyl Alcohol | 20 g |
| White Beeswax | 100 g |
| Arachis Oil | 305 g |
Extemporaneous preparation
The following directions apply.
Triturate the Zinc Oxide with a portion of the Virgin Castor Oil until smooth and add the mixture to the remainder of the ingredients previously melted together. Stir while cooling until the temperature is about 40°.
The ointment complies with the requirements stated under Topical Semi-solid Preparations and with the following requirements.
Content of zinc oxide, ZnO
7.0 to 8.0% w/w.
IDENTIFICATION
A. Heat 1.3 g of the ointment gently in a porcelain dish over a small flame until the basis is completely volatilised or charred. Increase the heat until all the carbon is removed. The residue obtained is yellow when hot and white when cold.
B. Dissolve the cooled residue obtained in test A in 5 mL of 1M hydrochloric acid. The resulting solution yields the reaction characteristic of zinc salts, Appendix VI.
ASSAY
Heat 1 g of the ointment gently in a porcelain dish over a small flame until the basis is completely volatilised or charred.
Increase the heat until all the carbon is removed. Dissolve the residue in 10 mL of 2M acetic acid and add sufficient water to produce 50 mL. To the resulting solution add 50 mg of xylenol orange triturate and sufficient hexamine to produce a violet-pink colour. Add a further 2 g of hexamine and titrate with 0.05M disodium edetate VS until the solution becomes yellow. Each mL of 0.05M disodium edetate VS is equivalent to 4.069 mg of ZnO.
