The Pharmaceutics and Compounding Laboratory
Accuracy in Measurements

Learning Objectives

Upon completion of this exercise, you should be able to:

  • Define percentage error and state the percentage error tolerated in most prescription formulas.
  • Calculate the potential percentage error for weighing a stated amount of a substance given the sensitivity of the balance.
  • Define least weighable quantity.
  • Calculate the least weighable quantity for any balance, given the allowed percentage error and the sensitivity of the balance.
  • Describe and/or demonstrate the proper techniques for using the Class III prescription balance and corresponding weights to measure solid or liquid substances with an error of measurement not to exceed 5%.
  • Differentiate between volumetric/nonvolumetric and TD/TC glassware or devices.
  • Select glassware/liquid measurement devices which are appropriate for a particular measurement operation.
  • Describe and/or demonstrate the proper techniques for using pipets, syringes, and graduates for measuring and delivering liquids.
  • Given the specific gravity or density of a compound, or references in which to locate these, perform calculations to convert the weight of the compound to its corresponding volume (or volume to corresponding weight).