Camphor

Rarely prescribed per se along with fats, but when that happens the only course is to dissolve the camphor in the melted basis, as in the case of the following prescription:

Here put a drachm of flowers of camphor in the vaseline melted in a 1-ounce quinine-bottle placed in a pan of hot water; shake until dissolved (which takes only a few seconds). Put the zinc oxide in a mortar and triturate with a few drachms of the camphorated vaseline until smooth, then add the rest.

Chloral Hydras

To look at, the following prescription would seem to provide a very hard ointment :

Melt the cocoa-butter and spermaceti, and when getting creamy add the chloral and menthol, previously powdered, and stir until cold. The chloral prevents the basis from becoming quite solid. Compare remarks on page 196.

Chrysarobin ('Chrysophanic acid'). - This should be dissolved, if possible, in the fatty basis of the ointment, but if there is not sufficient fat to form a perfect solution, it is preferable to rub the chrysarobin to fine powder, and gradually incorporate the solid basis with it. Chrysarobin is more soluble in castor oil than in lard.

Cocaine

This alkaloid is frequently prescribed to be dissolved in melted vaseline or lard. Ointments containing 1 of cocaine in 20, when prepared in this way, exhibit microscopic crystals on cooling. Wyatt finds that the alkaloid is soluble only to the extent of 1 in 150 of soft paraffin, and, taking advantage of its greater solubility in olive oil (1 in 20), suggests that each grain of cocaine should be rubbed with 20 minims of the oil before adding to the paraffin basis. The British Pharmacopoeia plan is to dissolve the alkaloid in four times its weight of oleic acid. When the ointment is for the eyes simply triturate the alkaloid with the cold basis. The salts should be dissolved in water before mixing with the fat prescribed.

Extracts should always be thinned and the fatty matter added in portions, as in the case of Mix the extract with the glycerin, then add the lard.

Liquid extracts are most easily incorporated with fatty bases by using a warm mortar;e.g., hamamelis ointment, B.P., cannot be satisfactorily and quickly made on a slab, but in a warm mortar it presents no difficulty.

Glycerin is most easily incorporated with fats by using a mortar which has been first thoroughly warmed with hot water.