(3) The other known factor is that the water will be added to 300 ml of 70%.
The 300-ml, because it pertains to the 70%, is placed on the line opposite the 70% on
the matrix (see above). Once there are two values on the line and two values on
225 ml of O% (Water)
NOTE: When distilled water, ointment bases, or normal saline are used as diluents,
they will contain zero percent (0%) active ingredient.
b. Example 2: How many grams of coal tar must be added to one pound of 2%
coal tar ointment to make a 4% coal tar ointment?
(1) This problem indicates a desired strength of 4% and a lower
strength of 2%. If no other strength is indicated, it can be assumed to be 100
percent. Coal tar is 100% coal tar.
(2) Because the question asks, "How many grams of coal tar?" and coal tar
is 100%, the X must be placed on the line opposite 100% (see above).