1. Dilution and Concentration

2. Dilution and Concentration
- Pharmaceutical preparations can be diluted by:
1- The addition of diluent.
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 weaker ones may be made.

3. 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 ??
Answer
1:5000 = x = %
5000
X = quantity of diluted solution x 0.02
Quantity of diluted solution = 1250 ml

4. 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.

5. 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?
Answer
X =
90 x =
0 x =
Totals:
% = / = 29%

6. 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 ??
Answer
50% parts of 50% ointment
20% parts of 20% ointment
10%
5% parts of 5% ointment