Traditionally, the breaking force of tablets has always been referred to as hardness. However, as the United States Pharmacopoeia (USP) points out, this term is really a misnomer since hardness refers to the resistance of a surface to penetration or indentation by a probe e.g., penetrometer.

For this reason, in its Chapter <1217>, USP refers to Tablet Breaking Force not hardness describing the breaking force of a tablet as being the force required to cause it to fail (i.e. break) in a specific plane.

The European Pharmacopoeia (Ph.Eur.), on the other hand, in its Chapter 2.9.8 uses the term crushing strength. Purists would, no doubt, argue that, in many cases, the tablet is not actually crushed, merely fractured, and that the term strength implies tensile strength as opposed to compressive load. Suffice it to say, all Copley Testers comply with the relevant Pharmacopoeias irrespective of the terminology employed.

The units of force normally employed to quantify breaking force are kiloponds or Newtons.

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