ROSIN-BASED POLYMER AS CREAM BASE 201 solution. One milliliter of phenolphthalein was added to the above mixture and titrated with 0.1 M KOH until the solution remained faintly pink after shaking for 30 seconds. The average of three readings was reported. The acid value = 5.61 N/W, where N is the number of milliliters of 0.1 molar KOH required, and W is the weight of the substance in grams. The specific gravity was determined using a simple displacement method using a gravity bottle as described in the Pharmacopoeia of India, 1996. The saponification value is the number of milligrams of KOH required to neutralize the free acid and to saponify the ester present in one gram of sample. It is determined as per the procedure described in the Pharmacopoeia of India, 1996. Four grams of rosin-based polymer was introduced into a 200-ml borosilicate glass fitted with a reflux condenser. To it 25 ml of ethanolic KOH was added along with a little pumice powder, and it was refluxed on a water bath for 30 minutes. One milliliter of phenolphthalein was added to it and titrated with 0.5 ml of HCL (a). The experiment was repeated omitting the rosin-based polymer (b). The saponification value = 28.05 (b - a)/w, where w is the weight of the substance taken. The HLB of the prepared rosin-based polymers for the present experiment was deter- mined by following a formula described by Griffin: HLB = 20 (1 - S/A), where S is the saponification number and A is the acid number of the acid. The viscosity of the prepared polymers was determined by using a Brookfield synchro- lectic viscometer, model RVT. The sample was taken in suitable size glass bottles, and the spindle was inserted in it up to the mark. Spindle number 1 was used in all the cases. The dial reading thus obtained was multiplied by the factor given in the chart supplied by the manufacturer. The composition of the polymers used to prepare the creams and their physicochemical properties are given in Tables I and II, respectively. PREPARATION OF THE CREAMS The ingredients used to prepare cream bases are listed in Table III. The cream bases were formulated using a regular fusion method: The surfactants (Tween 80/rosin-based) were added to water to which diclofenac diethylammonium was dissolved with constant stirring at 70øC in a glass beaker. Cetyl alcohol and stearyl alcohol were melted by heating at 70øC. The mixture ofpropylene glycol, isopropyl myristate, and glycerol was preheated to 70øC and added to the melted cetyl alcohol and stearyl alcohol. To this Table I Composition of Polymer 2 Composition Weight in grams Rosin 50 Castor oil 35 Glycerol 2.2 Sorbitol 14.7 Maleic anhydride 6 Pthaleic anhydride 2 Pentaerythritol

202 JOURNAL OF COSMETIC SCIENCE Table II Physicochemical Properties of Polymer 2 Weight Polymer Acid Sap per ml* Refractive index* number value value HLB Viscosity* (1% solution) (1% solution) Polymer 2 0.093 108.42 9.92 45000 1.2549 1.3335 * Readings taken at 37øC. Table III Formulation of Cream Bases Ingredients R2 RT Cetyl alcohol 5 % 5 % Stearyl alcohol 5 % 5 % Propylene glycol 5 % 5 % Isopropyl myristate 8% 8% Glycerin 5 % 5 % Polymer 2 2.5% -- Tween 60 -- 2.5% Diclofenac diethylammonium 1.16 1.16 Distilled water Up to 100 ml Up to 100 ml melted material the aqueous phase containing diclofenac diethylammonium and surfac- tant was added with continuous stirring at 70øC. The mixing was continued for five minutes with the help of a stirrer. The creams were then distributed to glass bottles and stored at various temperatures for stability studies. The evaluation data of the creams is presented in Table IV. SPREADABILITY The spreadability of the creams was evaluated by spreading a sufficient quantity of the cream on the hand. PREPARATION OF THE SKIN MEMBRANE Full-thickness abdominal skin was obtained from freshly sacrificed albino rats (Wistar strain male weight 200-250 g). It was washed thoroughly with distilled water to Table IV Evaluation Data of Prepared Creams Percent drug Formulation content Viscosity pH Homogeneity R2 97.5 6400 6.4 * RT 96 5600 6.3 * RM 98 6200 6.2 * * Indicates good homogeneity.