Units of Measurement
The units of measurement of tablet hardness mostly follows standards used in materials testing – the International System of Units.
- Kilogram (kg) – The kilogram is recognized by the SI system as the primary unit of mass.
- Newton (N) – The Newton is the SI unit of force; the standard for tablet hardness testing. 9.807 Newtons = 1 kilogram.
- Pound (lb) – Technically a unit of mass but can also be used for force and should be written as pound force or lbf in this case. Sometimes used for tablet strength testing in North America, but it is not an SI unit. 1 kilogram = 2.204 pounds.
- Kilopond (kp) – Not to be confused with a pound. A unit of force also called a kilogram of force. Still used today in some applications, but not recognized by the SI system. 1 kilopond = 1 kgf.
- Strong-Cobb (SC) – An ad hoc unit of force which is a legacy of one the first tablet hardness testing machines. Although the SC is arbitrary, it was recognized as the international standard from the 1950s to the 1980s. 1 Strong-Cobb represented roughly 0.7 kilogram of force or about 7 newtons. Although the Strong-Cobb unit is arbitrarily based on the dial reading of a hardness tester, it became an international standard for tablet hardness in the 1950s until it was superseded by testers using SI units in the 1980s. The Strong-Cobb is a unit with a very unusual name for a unit of measurement since it is named after the company, Strong-Cobb Inc. The inventor of the hardness tester was Robert Albrecht, the plant engineer for the Strong-Cobb Company. He sold the patent to the company for $1.00.
Read more about this topic: Strong-Cobb Unit
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