[Refractometric determination of the fat base content in emulsion ointments (author's transl)]

The Pharmacopoeia of the GDR provides no direct method for the determination of the fat base content in ointments. The indirect determination which is due to in calculating the difference between 100% and the percentages of all the other constituents is tedious and inexact. For this reason, it was tried to find a direct method which was to be reliable, rapid and easy. In principle, the refractometric method divised by Rudischer [2--5, 9] for the determination of fat in meat and meat products, which has been compulsory since 1965, is suitable for this purpose. Consequently, this method was adapted to the requirements of ointment analysis and subjected to modifications which resulted in the variant A for non-ionic ointments, and the variant B for ointments containing ionic fatty alcohol sulphates. The results obtained with the refractometric method from all kinds of ointments tested were in full agreement with the actual fat contents. Parallel determinations differed by 0.5% at the most.