*2.8.3 Tapped density*

It is measured by taking accurately weighed 10 g of powder blend into a 100 ml graduated measuring cylinder. The initial volume was determined. The cylinder was *Development of Liquisolid Compacts: An Approach for Dissolution Enhancement of Poorly… DOI: http://dx.doi.org/10.5772/intechopen.108706*

initially tapped for 200 times from a distance of 14 � 2 mm. The tapping process was again repeated additionally for 200 times. Finally, the tapped volume was noted [12]. The tapped density was calculated using Eq. (10) the following formula in gm/ml.

$$\text{Trapped density} = \frac{\text{Weight of power}}{\text{Tappend volume}} \tag{10}$$

#### *2.8.4 Carr's index or compressibility index*

Compressibility Index is calculated using Eq. (11) based on tapped and bulk densities which determines the ease of powder flow property.

$$\text{Compressibility index } (\%) = \frac{\text{Tapped Density-Bulk Density}}{\text{Tapped Density}} \times 100\tag{11}$$

#### *2.8.5 Hausner's ratio*

The Hausner's ratio is the proportion of a powder tapped density to its bulk density. It is calculated using Eq. (12).

$$\text{Hausner's ratio} = \text{Tapped density} / \text{Bulk density} \tag{12}$$

Powders with Hausner's ratio 1 to 1.11, 1.12 to 1.18, 1.19 to 1.25, 1.26 to 1.34, 1.35 to 1.60 indicate free flowing, good, fair, passable, poor flow of powder respectively.

The post compression tests for the prepared LSC formulations were performed similar to that of tablets according to IP specifications [21].

#### *2.8.6 Weight variation test*

The weight of tablet is determined to ensure that tablet contains exact amount of drug. Around 20 LSCs from each formulation were selected randomly. They were weighed individually and the average weight was calculated using digital balance. The individual weights were then compared with that of average weight for each formulation batch. It is calculated using Eq. (13) the below formula,

$$\% \text{Deviation} = \frac{(\text{Individual weight of table} - \text{Average weight tables})}{\text{Average weight of tables}} \times 100 \quad \text{(13)}$$

#### *2.8.7 Hardness*

It is also termed as crushing strength of tablet. It is measured using Monsanto hardness tester and was expressed in kg/cm2 . The LSC whose hardness to be tested was placed between the spindle and anvil of Monsanto hardness tester. The screw knob is moved clockwise and then pressure is applied that holds the tablet in position. The scale is moved in order that the indicator is fixed at zero. The pressure is applied continuously until tablet breaks. The reading is noted, that indicates the pressure required to break the tablet. The test is performed thrice and the mean value was determined.

### *2.8.8 Friability*

It is used to measure the mechanical strength of tablets. The friability of prepared LSCs can be determined using Roche friabilator (Mumbai, India). Around, 10 LSCs from each batch were weighed and placed in the chamber of friabilator. The chamber is rotated at speed of 25 rpm for a period of 4 min (100 rotations). At the end of test, the tablets were then dusted, re-weighed collectively and the percentage weight loss (friability) was calculated [22]. It is measured using Eq. (14)

$$\% \text{friability} = \frac{\text{Initial weight} - \text{final weight}}{\text{Initial weight}} \ge 100\tag{14}$$

## *2.8.9 Drug content uniformity*

About 10 LSCs were randomly selected and crushed to powder in a mortar. The powder was weighed equivalent to unit dose of drug which was taken into 100 ml volumetric flask. Initially, 10 ml volume of methanol was added, followed by addition of buffer to make up final volume. The resulting solution was diluted, filtered and analyzed using spectrophotometer to determine the drug content [19].

#### *2.8.10 Disintegration time*

Disintegration time for LSC was performed by placing one tablet in each of the six tubes of the basket of USP Disintegration Tester (Electrolab, India) apparatus. Disc was placed above each tube and the apparatus was run using buffer solution as immersion medium. The apparatus is maintained at temperature of 37 � 2°C. The assembly will be lifted up and down between 30 cycles/min. The time required for all the six tablets to disintegrate completely was noted as DT. The process is repeated thrice and the average disintegration time is determined [19].
