(3) Example #3: How many milliliters of paraldehyde are needed to make

120 ml of a 10% (v/v) paraldehyde solution?

IF

THEN

_______ = ________

Answer: 12 ml of paraldehyde

be labeled as to what they represent. A 10% paraldehyde solution

contains 10 milliliters of paraldehyde in each 100 ml of solution and the first

ratio of the proportion should indicate this (see below). The question asks,

"How many milliliters of paraldehyde are needed?" therefore, the X value must

be placed in the proportion opposite the 10 ml of paraldehyde in the first ratio.

The 120 ml represents final solution.

IF

10 ml paraldehyde

= THEN

X ml paraldehyde

100 ml of solution

120 ml of solution

100 X =

1200

X

=

12 ml of paraldehyde

c. One percent Method: The 1 percent Method is used only to find the amount

of active ingredient when the final volume or weight of the preparation is known. This

method cannot be used to calculate the amount of preparation that can be made when

the percentage strength and the amount of active ingredient is known.

1 percent Method:

Formula:

(1 percent of the total amount of preparation) X (number of percent) =

The amount of active ingredient)

decimal point on the total amount of preparation two places to the left.

Sample Problems:

(1) Example #1: How many grams of ephedrine sulfate are needed to make

120 ml of a 2% (w/v) ephedrine sulfate solution?

(a)

Find the total amount of preparation:

The total amount is 120 ml

MD0802

2-14

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