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Sample Size same material compressed under conditions identical to those of thinner tablets, with the same tooling shape and to In order to achieve sufficient statistical precision for the the same peak force, will require greater breaking forces. determination of average breaking force, a minimum of 6 Tablet orientation and failure should occur in a manner con- tablet samples should be tested. The average breaking force sistent with those used during the development of the dos- alone may be adequate to fulfill the purpose of process or age form. For direct comparisons (i.e., without any normal- product quality control. In cases where breaking force may izations of the data), breaking force measurements should be particularly critical, the average plus individual breaking be performed on tablets having the same dimensions, ge- force values should be accessible. Non-Pharmacopoeial or Non-Official Tests These are tests that are performed on tablets and which are not listed in official compendia and concern a variety of quality attributes that need to be evaluated, such as the porosity of tablets, hardness or crushing strength test, friability test, tensile strength determination, thickness test etc. Some of these tests have no officially set limits for acceptance or rejection and thus may vary from manufacturer to manufacturer and from formulation to formulation. Crushing strength and friability appeared in the 2001 Edition of British Pharmacopoeia (Appendix A324). There was however no definite set limits. The two tests are, therefore, here considered under non-pharmacopoeial tests. Tablet Hardness or Crushing Strength Test This measures the degree of force (in kilograms, pounds, or in arbitrary units) needed to fracture a tablet. Besides the concentration of binders used and the compression force, the hardness of a tablet depends on The characteristics of the granules to be compressed e.g., hardness and deformation under load. The type and concentration of lubricant used and The space between the upper and lower punches at the time of compression. The crushing strength of tablets is usually checked using Monsanto or Stokes hardness tester, Strong-Cobb hardness tester and the Pfizer crushing strength tester. All are manually used. So, strain rate depends on the operator. A force of about 4 kg is considered the minimum requirement for a satisfactory tablet. Measurement is usually carried out using a minimum of ten tablets Where F is the force needed to fracture a cylindrical flat-faced tablet of thickness t along its diameter D.