Methods of emulsion preparation
There are two methods of
preparing a primary emulsion:
1-Dry gum method:-
Emulsifier (acacia) is mixed
with oil before water addition.
•The
quantities of oil, water and gum for primary emulsion are calculated. The
acacia and the oil are placed in a dry porcelain mortar. When the acacia is
thoroughly distributed throughout the oil, Water is added, all at once. The
mixture is triturated continuously but lightly in one direction until the
mixture thickens under the pestle.
•The primary emulsion is triturated for at least 5 minutes. Finally, the emulsion is transferred to a graduated cylinder and brought to volume with water. The emulsion should be Labeled "Shake well before use.
2-Wet gum method:
•The primary emulsion is triturated for at least 5 minutes. Finally, the emulsion is transferred to a graduated cylinder and brought to volume with water. The emulsion should be Labeled "Shake well before use.
2-Wet gum method:
Emulsifier is added to water to form a
mucilage then oil is slowly added to emulsion.
nThequantitiesofoil,waterandgumforprimaryemulsionarecalculated.Acaciaandwateraretrituratedtoformmucilageinaporcelainmortar.TheoilisaddedinSmallamountswithconstant,rapidandlighttrituration.Whenalltheoilhasbeenadded,themixtureistrituratedvigorouslyforafewminutes.Finally,theemulsionistransferredtograduatedcylinderandbroughttovolumewithwater.
•Emulsions containing more than one oily liquid:
•Emulsions containing more than one oily liquid:
nWhen two
or more oily liquids are present, the quantity of acacia required for each is
calculated, and the sum of these quantities is used for the emulsion.
Alternatively each oil may be emulsified separately before mixing.
•Emulsions containing water-soluble
substances:
nMost of the substances included in emulsions
are water-soluble, e.g. salts, syrups, glycerin. Water-soluble substances are
dissolved in the aqueous vehicle required for the approximate completion of the
desired volume in this way are used in a dilute state as possible because some
substances have "de -emulsifying" properties, i.e. they might
unstabilize the emulsion if added in concentrated solution.
•Emulsions containing oil-soluble substances:
•Emulsions containing oil-soluble substances:
nE.g.,Salol and naphthol
nEmulsion containing oil-soluble substances, should be prepared with 50 % more Gum than required for other emulsions. The oil-soluble substances are dissolved in the Oil before preparing the primary emulsion.
•Emulsions containing substances insoluble in either oil or water
nThese substances must be finely powdered in a mortar, and mixed with the acacia required for the primary emulsion. The oil is then added, and the primary emulsion prepared in the usual way.
nExample: Bismuth carbonate in a castor-oil emulsion, and phenolphthalein in a liquid paraffin emulsion.
•Emulsions containing a small proportion of oily substances:
nIf the proportion of oil is too small, modifications must be made. Acacia emulsions containing less than 10% oil tend to cream readily. An inert oil, such as arachis oil, should be added to increase the amount of oil to 10 -20%, and so prevent this from happening.
nEmulsion containing oil-soluble substances, should be prepared with 50 % more Gum than required for other emulsions. The oil-soluble substances are dissolved in the Oil before preparing the primary emulsion.
•Emulsions containing substances insoluble in either oil or water
nThese substances must be finely powdered in a mortar, and mixed with the acacia required for the primary emulsion. The oil is then added, and the primary emulsion prepared in the usual way.
nExample: Bismuth carbonate in a castor-oil emulsion, and phenolphthalein in a liquid paraffin emulsion.
•Emulsions containing a small proportion of oily substances:
nIf the proportion of oil is too small, modifications must be made. Acacia emulsions containing less than 10% oil tend to cream readily. An inert oil, such as arachis oil, should be added to increase the amount of oil to 10 -20%, and so prevent this from happening.
