Related entry: Cera Alba (U. S. P.)—White Wax - Cera Flava (U. S. P.)—Yellow Wax
Other tomes: BPC - AJP1883
Cerates are agents intended for external application, and are composed of wax, or spermaceti, combined with fatty matters, and with which resins, powders, etc., are frequently amalgamated. The articles entering into their composition should always be fresh, especially the fats, as these preparations are very prone to rancidity; the addition of benzoic acid tends to prevent this change, but its presence is not always desirable. Prof. E. S. Wayne found that by substituting paraffin for the wax, in cerates and ointments, the disposition to decompose was considerably retarded. Cerates are firmer in consistence than ointments, and are intended more as a sort of plaster than for inunction. The cerate is intermediate in consistence between the ointment and the plaster, about the consistence of cold butter, and may be spread with a spatula upon cloth or other substance, and be applied to the body, to which it will adhere without melting. In the preparation of cerates the water-bath will be found preferable to a direct exposure to the fire; and to effect the fusion of the materials, a very moderate heat will be sufficient. During the cooling of the compound it should be constantly and thoroughly stirred, not permitting one part to solidify before another. Cerates should be made in small quantity at a time, and should be kept in a cool place, in jars closely covered with tin foil, so as to exclude the air as much as possible. It was at one time thought that the use of wax in these preparations would be entirely superseded by paraffin, which does not become rancid, but experience has shown it to be objectionable on account of the granular character it gives to the cerate. Yellow wax is found to be less liable to become rancid than white wax.