a. Description. A saturated solution is a solution--at a specified temperature--
that cannot dissolve any additional solute. A solution saturated at 25Centigrade (C)
will become unsaturated if the temperature rises above 25 C. At cooler temperatures,
it will become supersaturated; that is, it will contain more solute than would normally
dissolve at the cooler temperature. Some of the solute is likely to precipitate and make
the solution cloudy. For this reason, it is best to make "saturated" solutions so that they
would be saturated at about 20 C, regardless of the room temperature at the time of
b. Preparation of Saturated Solution of Potassium Iodide. When the
physician prescribes "saturated solution of potassium iodide" (SSKI), he is actually
referring to Potassium Iodide Solution, NF. Consult the United States
Pharmacopoeia/National Formulary when you need to prepare this solution.
a. Description. Stock solutions, either purchased or prepared in advance, are
solutions of known concentration used in the manufacture of other preparations and in
the compounding of prescriptions. They save time and provide a convenient method for
accurately measuring small amounts of drugs to be dissolved in solutions. Since they
are of known concentration, a prescribed amount of the dissolved ingredient can be
accurately and quickly withdrawn by measuring out the volume of stock solution
containing it. The more stable and frequently prescribed agents in solutions can be
prepackaged in a standard concentration in your pharmacy. When a prescription
requires a certain number of milligrams (mg) of a drug in a liquid preparation, it is not
necessary for you to weigh out the amount each time, but only to measure out the
number of milliliters (ml) which contain the desired amount of milligrams of solute. This
can then be diluted to the desired volume or mixed with the mixture being prepared.
b. Stability. To enhance the keeping quality of your stock solutions, make them
under aseptic conditions, using distilled water that has been recently boiled and cooled.
Sterilize the stock bottles (amber colored ones are preferred) and store the solutions in
a cabinet or other place as free from light as is feasible. Putting the amber bottle inside
a cardboard container gives additional protection.
c. Precautions. Some important things to remember about stock solutions are:
(1) If the stock solution is to be used in the future, it must be stable or used