(c) Porcelain mortars. Porcelain mortars are useful in making
emulsions or solutions not involving staining substances. Porcelain mortars and pestles
are fragile, as are glass and wedgewood, and any heavy crushing should be performed
using other methods.
(3) Spatulas. Although spatulas play a more important role in other
procedures and techniques (for example, levigation), they are used in scraping down
the sides of the mortar in trituration. A spatula resembles a knife in having a handle and
a blade. The blade, which varies in size, is very flexible and dull. The spatula is
probably the most frequently used tool in the pharmacy. Spatulas may be made of
metal (preferably stainless steel) or of hard rubber. The type used depends upon the
substances being processed.
b. Pulverization by Intervention. This is the process of reducing a substance
to a powder by dissolving it in a small amount of volatile solvent and triturating until dry.
For example, to powder camphor, dissolve the camphor in a small amount of alcohol,
triturate until the alcohol evaporates and the resulting substance will be a powder.
c. Levigation. Levigation is a process by which the particle size of substances
is reduced by making a paste of the substances, using a liquid in which they will not
dissolve such as water, glycerin, or mineral oil. This paste forms the basis for a
medicinal. This process may be accomplished either in a shallow mortar or on an
ointment slab. Levigation is a valuable process in compounding ointments that include
a powder. It makes a much more elegant, nongritty product in a considerably shorter
time than does simple incorporation.
Section V. SEPARATION
There are frequent occasions in pharmacy when it is necessary to separate the
individual components of substances. Such procedures may be performed after
preparation (for example, filtering out foreign particles) or may be performed while
making the preparation as in the formation of a desired precipitate.
1-13. SEPARATION BY HEAT
a. We will now discuss the separation of different substances, not just the
separation of different particle sizes. The first of these is separation by heat.
Previously, in the section dealing with the application of heat, we defined a number of
processes; of those processes, the following are methods of separation: