Is true density also known as tap density?
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TAPPED DENSITYTapped density is achieved by mechanically tapping a measuring cylinder containing a powder sample. After observing the initial volume, the cylinder is mechanically tapped, and volume readings are taken until little further volume change is observed. The mechanical tapping is achieved by raising the cylinder and allowing it to drop under its own weight a specified distance by either of two methods as described below. Devices that rotate the cylinder during tapping may be preferred to minimize any possible separation of the mass during tapping down.Method IProcedure—Unless otherwise specified, pass a quantity ofmaterial sufficient to complete the test through a 1.00-mm(No. 18) screen to break up agglomerates that may have formed during storage. Into a dry 250-mL glass graduatedcylinder (readable to 2 mL) weighing 220 ± 44 g and mounted on a holder weighing 450 ± 10 g introduce, without compacting, approximately 100 g of test sample,M,weighed with 0.1% accuracy. If it is not possible to use 100 g, the amount of the test sample may be reduced andthe volume of the cylinder may be modified by using a suitable 100-mL graduated cylinder (readable to 1 mL) weighing 130 ± 16 g and mounted on a holder weighing 240 ± 12 g. The modified test conditions are specified with the results. Carefully level the powder without compacting, if necessary, and read the unsettled apparentvolume,Vo, to the nearest graduated unit.Mechanically tap the cylinder containing the sample by raising the cylinder and allowing it to drop under its own weight using a suitable mechanical tapped density tester that provides a fixed drop of 14 ± 2 mm at a nominal rate of 300 drops per minute. Unless otherwise specified, tap the cylinder 500 times initially and measure the tapped volume,Va, to the nearest graduated unit. Repeat the tapping an additional 750 times and measure the tapped volume,Vb, to the nearest graduated unit.[NOTE—Fewer taps may be appropriate, if validated, for some powders.]If the difference between the two volumes is less than 2%,Vbis the final tapped volume,Vf. Repeat in increments of 1250 taps, as needed, until the difference between succeeding measurements is less than 2%. Calculate the tapped density, in g per mL, by the formula:(M) / (Vf).Generally replicate determinations are desirable for the determination of this property.Method IIProceed as directed underMethod Iexcept that a suitable mechanical tapped density tester that provides a fixed drop of 3 mm (±10%) at a nominal rate of 250 drops per minute is used...
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TAPPED DENSITYTapped density is achieved by mechanically tapping a measuring cylinder containing a powder sample. After observing the initial volume, the cylinder is mechanically tapped, and volume readings are taken until little further volume change is observed. The mechanical tapping is achieved by raising the cylinder and allowing it to drop under its own weight a specified distance by either of two methods as described below. Devices that rotate the cylinder during tapping may be preferred to minimize any possible separation of the mass during tapping down.Method IProcedure—Unless otherwise specified, pass a quantity ofmaterial sufficient to complete the test through a 1.00-mm(No. 18) screen to break up agglomerates that may have formed during storage. Into a dry 250-mL glass graduatedcylinder (readable to 2 mL) weighing 220 ± 44 g and mounted on a holder weighing 450 ± 10 g introduce, without compacting, approximately 100 g of test sample,M,weighed with 0.1% accuracy. If it is not possible to use 100 g, the amount of the test sample may be reduced andthe volume of the cylinder may be modified by using a suitable 100-mL graduated cylinder (readable to 1 mL) weighing 130 ± 16 g and mounted on a holder weighing 240 ± 12 g. The modified test conditions are specified with the results. Carefully level the powder without compacting, if necessary, and read the unsettled apparentvolume,Vo, to the nearest graduated unit.Mechanically tap the cylinder containing the sample by raising the cylinder and allowing it to drop under its own weight using a suitable mechanical tapped density tester that provides a fixed drop of 14 ± 2 mm at a nominal rate of 300 drops per minute. Unless otherwise specified, tap the cylinder 500 times initially and measure the tapped volume,Va, to the nearest graduated unit. Repeat the tapping an additional 750 times and measure the tapped volume,Vb, to the nearest graduated unit.[NOTE—Fewer taps may be appropriate, if validated, for some powders.]If the difference between the two volumes is less than 2%,Vbis the final tapped volume,Vf. Repeat in increments of 1250 taps, as needed, until the difference between succeeding measurements is less than 2%. Calculate the tapped density, in g per mL, by the formula:(M) / (Vf).Generally replicate determinations are desirable for the determination of this property.Method IIProceed as directed underMethod Iexcept that a suitable mechanical tapped density tester that provides a fixed drop of 3 mm (±10%) at a nominal rate of 250 drops per minute is used...
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