micromeritics l3: densities of powders- porosity, void and bulk volume

• porosity

• true volume

• bulk volume

• apparent density

• true density

• bulkiness

The characteristics used to describe powders include

Packing and flow

they affect the size of the container required for packaging, the flow of granulations, the efficiency of the filling apparatus for making tablets and capsules, and the ease of working with the powders.

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TRUE VOLUME

VOLUME of material without VOIDS (intra-and inter-)

GRANULAR VOLUME

VOLUME of material with intraparticular voids

BULK VOLUME

VOLUME of material with VOIDS (intra-and inter-)

BULK VOLUME – TRUE VOLUME

VOID VOLUME = ___ – ___

TRUE DENSITY

density of material itself exclusive of inter- and intraparticular voids

GRANULAR DENSITY

density of material itself including intraparticular voids

BULK DENSITY

density of material itself inclusive of inter- and intraparticular voids

TAPPED DENSITY

a.k.a. COMPRESSED BULK DENSITY

TAPPED DENSITY

density obtained after compaction by tapping or vibration

determinaation of bulk density method I formula

method I - Graduated Cylinder

method II - Scott Volumeter

determination of bulk densities methods

Mechanical tapping (Determination of Tapped Density)

___ is achieved by raising the cylinder and allowing it to drop under its own weight

poorer

Carr reported that the more a material is compacted in a compaction or tap bulk density test, the ___ are its flow properties.

Compressibility (Carr’s) Index formula

< 10

Compressibility (Carr’s) Index (%) of excellent flow character

11-15

Compressibility (Carr’s) Index (%) of good flow character

16-20

Compressibility (Carr’s) Index (%) of fair flow character

21-25

Compressibility (Carr’s) Index (%) of passable flow character

26-31

Compressibility (Carr’s) Index (%) of poor flow character

32-37

Compressibility (Carr’s) Index (%) of very poor flow character

> 38

Compressibility (Carr’s) Index (%) of very, very poor flow character

porosity

•A measure of the air spaces or voids in a material ε → ”epsilon”

porosity formula

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1.50 g/ml

true density of starch

1.54 g/ml

true density of citric acid

2.70 g/ml

true density of talc

2.05 g/ml

true density of activated carbon

cubic

lowest packing porosity = 48%

48%

cubic - lowest packing porosity = __

rhombohedral

closest packing porosity = 26%

26%

Rhombohedral closest packing porosity = __