Dilution and concentration

							Dilution and Concentration
            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.
                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 = 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?

                               Answer
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 ??

                        Answer
       50%               5 parts of 50% ointment

       20%                5 parts of 20% ointment
               10%
       5%                 40 + 10 parts of 5% ointment