VPT 311: General and Systemic Veterinary Pharmacology (2+1)

ALLIGATION ALTERNATE 

• It is the method used to 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.
• If the percent of strength of the two solutions are a and b, the percent desired is c and if we consider the proportional parts required are x and y, then x and y can be determined by the following relationship;

x / y = c – b / a – c

• where ’a’ is the strength in % of the stronger solution and ‘b’ is the strength in % of the weaker solution.

Diagrammatically, this can be found out as follows:

    

• The result is x parts of solution of per cent a and y parts of solution of per cent b if mixed together will yield a solution of per cent c.