Using the triangle:
milliliters = 45
= 36 (answer)
(3) In the place of weighing 45 grams of glycerin, 36 milliliters of glycerin
may be measured.
f. Example problem. What is the weight in grams of 240 milliliters of light
liquid petrolatum having a specific gravity of 0.81?
g = sp gr X ml
g = 0.81 x 240
g = 194.4 (answer)
240 milliliters of light liquid petrolatum weighs 194.4 grams.
g. Example problem. The following prescription has all of the amounts indicated
as grams with the exception of mineral oil. Because mineral oil is a liquid, the units, as
written on this prescription, are milliliters. In compounding this prescription, all of the
substances must be weighed or measured separately and then combined by a certain
procedure. It is impractical to "q.s." with an ointment base. Instead, the weights of all
the other ingredients must be totaled and this combined weight must be subtracted
from the total amount of the preparation to find the amount of white petrolatum needed.
To accomplish this, the weight of the 8 milliliters of mineral oil must be calculated.
Specific gravity of mineral oil = 0.85.