Carr index
The Carr index is an indication of the compressibility of a powder. It is calculated by the formula <math>C=100\frac{V_B-V_T}{V_B}</math>, where <math>V_B</math> is the freely settled volume of a given mass of powder, and <math>V_T</math> is the tapped density of the same mass of powder. It can also be expressed as <math>C=100\times(1-\frac{\rho_B}{\rho_T})</math>, where <math>\rho_B</math> is the freely settled bulk density of the powder, and <math>\rho_T</math> is the tapped density of the powder.
The Carr index is frequently used in pharmaceutics as an indication of the flowability of a powder. A Carr index greater than 25% is considered to be an indication of poor flowability, and below 15%, of good flowability.[1]
The Carr index is related to the Hausner ratio, another indication of flowability, by the formula <math>C=100\times(H-1)</math>.
References
Mark Gibson (2001). Pharmaceutical Preformulation and Formulation: A Practical Guide from Candidate Drug Selection to Commercial Dosage Form. Boca Raton: CRC Press. ISBN 1-57491-120-1.
- ↑ Kanig, Joseph L.; Lachman, Leon; Lieberman, Herbert A. (1986). The Theory and Practice of Industrial Pharmacy (3 ed.). Philadelphia: Lea & Febiger. ISBN 0-8121-0977-5.