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4.32 APPARENT VOLUME

      This test for apparent volume is intended to determine under defined conditions the apparent volumes, before and after settling, the ability to settle and the apparent densities of divided solids (for example, powders, granules).

Apparatus

      The apparatus is specified in Fig. 1 and consists of the following components:

      (a) A settling apparatus capable of producing in 1 minute 250±15 taps from a height of 3±0.2 mm. The support for the graduated cylinder, with its holder, has a mass of 450±5 g.

      (b) A 250-ml graduated cylinder (2-ml intervals) with a mass of 220±40 g.

Procedure

      Into the dry cylinder, introduce without compacting 100.0 g (W) of the substance being examined. If this is not possible, select a test sample with an apparent volume between 50 and 250 ml and specify the weight in the expression of results. Secure the cylinder in its holder. Read the unsettled apparent volume, V₀, to the nearest millilitre. Carry out 10, 500 and 1250 taps and read the corresponding volumes V₁₀, V₅₀₀ and V₁₂₅₀, to the nearest millilitre. If the difference between V₅₀₀ and V₁₂₅₀ is more than 2 ml, carry out another 1250 taps.

Calculation 

      (a) Apparent volumes: – apparent volume before settling or bulk volume: V₀ ml.– apparent volume after settling or settled volume: V₁₂₅₀ or V₂₅₀₀. 

      (b) Ability to settle: difference V₁₀ ml – V₅₀₀ ml.

      (c) Apparent densities:

      The apparent densities are expressed as follows: – apparent density before settling or density of bulk product: W/V₀, in g per ml (bulk or poured density).

      – apparent density after settling or density of settled product: W/V₁₂₅₀ or W/V₂₅₀₀, in g per ml (tapped density).