What is carr's index and how does it influence tablet preparation?

Answer 1

One important characteristic is tapped bulk density, or simply tapped (tap) density: that is, the maximum packing density of a powder (or blend of powders) achieved under the influence of welldefined, externally applied forces. The minimum packed volume thus achieved depends on a number of factors including particle size distribution, true density, particle shape and cohesiveness due to surface forces including moisture. Therefore, the tap density of a material can be used to predict both its flow properties and its compressibility (see right sidebar as to how). These are just two of the many parameters which are important in the overall tabletting process - which requires that loose powders be compacted into a durable solid form with the correct mechanical strength, porosity and dissolution characteristics – and in capsulefilling performance. Compressibility Index & Hausner Ratio The two most commonly used measures of the relative importance of interparticulate interactions are the compressibility index (often referred to as Carr’s Index [1]) and the Hausner ratio [2] (see right sidebar). “V” and “D” represent powder volume and density respectively, subscript “o” denotes the initial or untapped state and “f” the final or tapped state. In free-flowing powders the initial bulk and tapped densities will be more similar than in poor flowing powders which yield greater differences between the two values.