Question

Give an example formulation of a pharmaceutical product using either Alligation alternate or Allegation medial.

Ex. How to make 70% ethyl alcohol or 3% hypertonic NSS.

Answer 1

Alligation alternate:

Example: If a pharmacist have to prepare 50% sorbitol solution from 70% and 40 % sorbitol solution.

First of all prepare the check board ( as shown in picture1 ) the write the higher concentration on top left I.e; 70% and lower concentration on bottom left ie 40 % and the required 50% in the center. then subtract the central value diagonally and the write on the right side of the board. Like 70- 50 = 20 so 20 will be written on the bottom right. Then 50-40 = 10 and will be written on the top right. So the proportion obtained is 10: 20 or 1 : 2 that implies 1 part of 70% sorbitol is taken and 2 parts of 40% sorbitol and are mixed together to obtain 50% sorbitol ointment.