On the Analysis of the More Commonly Used Ointments of the 'British Pharmacopœia' Containing an Inorganic Principle as the Active Constituent

In studying the analysis of ointments of this type, it was found that not all of the methods previously described are entirely satisfactory. Thus in the determination of mercury volumetrically by the thiocyanate process the results tend to be low. Dissolving out the fatty bases with a suitable solvent such as ether may sometimes be accomplished, but the process is often tedious, and if an apparatus such as the Soxhlet is used it is difficult to prevent some of the nonfatty substance being carried over with the ether to a greater or less extent. The methods described below have been investigated and found to give reliable results.