Section III. DILUTION OF STOCK PREPARATIONS
2-7. INTRODUCTION
Pharmacy personnel will often go to a stock solution to obtain the amount of
active ingredient that is needed to make a preparation. This is especially true if the
amount required is so small that it cannot be accurately weighed on a torsion balance.
It is easier to measure an amount of stock solution than to set up a balance, weigh the
ingredients, and compound the entire product. The use of stock preparations is an
important aspect of pharmacy.
2-8. FORMULAS: In order for these formulas to work:
a.
Volumes and weights must be expressed in the same units.
b.
Concentrations must be expressed in the same units.
c.
Formula: V C = V1 C1
(1) V = Volume of stock preparation
(2) C = Concentration of stock preparation
(3) V1 = Volume of desired preparation
(4) C1 = Concentration of desired preparation
d.
Formula: W C = W1 C1
(1) W = Weight of stock preparation
(2) C = Concentration of stock preparation
(3) W1 = Weight of desired preparation
(4) C1 = Concentration of desired preparation
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