There are 7680 m. in 1 pint of solution (water); therefore we divide
7680 by 500 as follows:
500)7680(15⅗ m. to 1 pint of solution (water).
500
————
2680
2500
————
1800
1500
————
300, or ⅗ of a m.
N.B.—Divide the number of m. in 1 pint by the strength of the solution,
and then divide the result by the percentage of original strength of
the article.
When original strength of solution is less than 100 per cent., as, for
example, formaldehyd, which is 40 per cent., divide the quotient above
resulting by the percentage of strength—viz.:
40)1536(38⅖ m. to 1 pint of solution (water).
120
———
336
320
———
¹⁶/₄₀ = ⅖.
To get a ¹/₁₀₀ of a grain dose of any drug out of a solution of 60
minims containing ¹/₃₂ of a grain of that drug, compute as follows:
³²/₃₂ or 1 grain = 32 × 60, or 1920 m.
¹/₁₀₀ = ¹/₁₀₀ of 1920 m.
100)1920(19⅕ m.
100
———
920
900
———
20, or ⅕ m.
RULE.—Multiply the quantity of the solution on hand in minims by a
number indicating the fractional amount of the drug therein contained,
and divide by a number indicating the fractional amount of the drug
desired.
In 20 parts of solution we have 1 part of carbolic acid.
In 1 part “ “ ¹/₂₀ “ “
In 100 parts “ “ 100 × ¹/₂₀ = 5 pt. “
So that ¹/₂₀ solution is a 5 per cent. carbolic acid solution.
40 parts contain 1 part of carbolic acid.
1 part contains ¹/₄₀ “ “
100 parts contain 100 × ¹/₄₀ = 2½ parts of carbolic acid.
So that ¹/₄₀ solution is a 2½ per cent. carbolic acid solution.