• Source: Hausner ratio

The Hausner ratio is a number that is correlated to the flowability of a powder or granular material. It is named after the engineer Henry H. Hausner (1900–1995).
The Hausner ratio is calculated by the formula




H
=



ρ

B



ρ

T






{\displaystyle H={\frac {\rho _{B}}{\rho _{T}}}}


where




ρ

B




{\displaystyle \rho _{B}}

is the freely settled bulk density of the powder, and




ρ

T




{\displaystyle \rho _{T}}

is the tapped bulk density of the powder. The Hausner ratio is not an absolute property of a material; its value can vary depending on the methodology used to determine it.
The Hausner ratio is used in a wide variety of industries as an indication of the flowability of a powder. A Hausner ratio greater than 1.25 - 1.4 is considered to be an indication of poor flowability. The Hausner ratio (H) is related to the Carr index (C), another indication of flowability, by the formula



H
=
100

/

(
100
−
C
)


{\displaystyle H=100/(100-C)}

. Both the Hausner ratio and the Carr index are sometimes criticized, despite their relationships to flowability being established empirically, as not having a strong theoretical basis. Use of these measures persists, however, because the equipment required to perform the analysis is relatively cheap and the technique is easy to learn.




References






General Bibliography


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.

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