PREPARATION OF SOLUTIONS
a. It is impossible to fully discuss the preparation of solutions in this subcourse.
If you desire a thorough discussion of this topic, you should seek an appropriate
reference (that is, Remington's Pharmaceutical Sciences).
b. The following are three basic methods of preparing official solutions:
Simple solution. An example is Potassium Iodide Solution, NF.
Chemical reaction. An example is Magnesium Citrate Solution, NF.
Extraction. This method is rarely used in the modern pharmacy.
NOTE: Because of special considerations and procedures which must be used in the
preparations of ophthalmic solutions, ophthalmic solutions will not be
discussed in this chapter. See Lesson 7.
When a single substance is dissolved in a solvent, a simple solution results.
Simple solutions are used both as complete medicinal agents and as vehicles or
ingredients in more complex preparations.
a. Preparation of the Simple Solution. For the most part, few difficulties are
encountered with simple solutions. Preparing them generally consists of mixing the
solute with the solvent and stirring or shaking until the solute goes into solution.
(1) Readily soluble substances. Readily soluble substances are added to a
portion of the solvent in a graduate and stirred with a glass-stirring rod until solution is
effected. The remainder of the solvent is then added and the combination stirred further
until the finished volume is reached. The resulting solution should be filtered, if
(2) Slowly soluble substances. With slowly soluble or very insoluble
solutes, best results are obtained by placing the solute in a mortar and adding portions
of the solvent to it with constant trituration. Fine powders, particularly, tend to float on
the surface if they are added to the solvent. They should be placed in a mortar,
moistened with a very small amount of solvent, and then brought up to volume with
b. Forms of Solids. The solids that you will dissolve are usually available in
three commercial forms: powdered, granular, and crystalline. The finer a drug is in
subdivision, the more quickly it will be soluble.