(11) Example problem: How many grams of potassium permanganate
(KMnO4) are needed to make this prescription?
(a) Before beginning the calculation, the prescription must be analyzed
to see exactly what the physician wants. The prescription states that the pharmacist
should dispense a solution of potassium permanganate in distilled water. The solution
should have a strength equivalent to 1 gram per 5000 milliliters and the pharmacist
should dispense 120 milliliters of the solution. The expression of strength will be the
1 gram =
_______________
5000 ml
(b) Assign the X value:
1 gram
=
X gram__
5000 ml
(c) Find the other known factor:
1 gram
=
X gram___
5000 ml
120 ml
(d) Then, cross-multiply:
5000 (x)
=
1 (120)
5000 x
=
120
(e) Solve for X:
X
=
120
5000
X
=
0.024
X
=
0.024 gram
MD0802
1-39