# Dilution and concentration by yaoyufang

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```									Dilution and Concentration
Dilution and Concentration
- Pharmaceutical preparations can be diluted by:
2- Admixture with solutions of lower strength.

- Pharmaceutical preparations can be concentrated by:
1- The addition of active ingredient.
2- Admixture with solutions of greater strength.
3- Evaporation of the diluent.

- Stock solutions: They are strong solutions from which
Dilution and Concentration
(quantity) x (concentration) (Concentrated mixture) =
(quantity) x (concentration) (Diluted mixture)

Example
How many milliliters of a 1:5000 (w/v) solution of phenylmercuric
acetate can be made from 125 ml of a 0.2% solution ??

1:5000 = 1   x 100 = 0.02 %
5000

125 X 0.2 = quantity of diluted solution x 0.02
Quantity of diluted solution = 1250 ml
Alligation
Definition: is an arithmetical method of solving problems
that involve the mixing of solutions or mixtures of solids
possessing different percentage strengths.

Alligation medial: is a method by which the percentage
strength of a mixture of two or more substances whose
quantities and concentrations are known may be
calculated.

Alligation alternate: is a method by which we may calculate
the number of parts of two or more components of a
given strength when they are to be mixed to prepare a
mixture of desired strength.
Alligation
Examples
1- What is the percentage (v/v) of alcohol in a cough mixture containing
500 ml of terpin hydrate elixir, 100 ml of chloroform spirit, and
enough hydriodic acid syrup to make 1000 ml? Terpin hydrate
elixir contains 40% (v/v) of alcohol, and chloroform spirit contains
90% (v/v) of alcohol?

40 X 500 =        20000
90 x 100 =        9000
0 x 400 =             0

Totals: 1000      29000

% = 29000 / 1000 = 29%
Alligation
2- A hospital pharmacist wants to use three lots of
ichthammol ointment containing respectively 50%, 20%
and 5% of ichthammol. In what proportion should they be
mixed to prepare a 10% ichthammol ointment ??