Autotap Bulk Density Analyzer for Solids

Autotaps and Dual Autotaps have been used around the world for decades to provide customers with consistent, reliable bulk density and flowability values – essential knowledge for measuring pharmaceut

 · 2 min read

The Autotap and Dual Autotap tapped density analyzers for powders are simple-to-use, automated devices which comply with a large number of internationally recognized standard methods. They provide a high level of test method control with a user-selectable, lockable number of taps. Tapping rate and drop height are fixed to provide consistent results from sample to sample. A large range of sample sizes can be accommodated with the use of a number of different graduated cylinder sizes.

The design of Autotaps and Dual Autotaps ensures compliance with all internationally recognized standard test methods describing the use of tapped density to determine bulk density involving a device capable of ensuring a drop height of 3 mm, a tapping frequency between 250 and 300 taps per minute, and the use of a specific type of graduated cylinder.

HOW TO Use the Autotap Bulk Density Analyzer

Many materials (such as powders) often display complex shapes or are too small to measure their dimensions accurately enough to determine their densities with a high certainty. Tapped density measurements can be used to predict flow and compressibility properties.

This value is obtained by mechanically tapping a volumetric vessel containing a known amount of sample a fixed distance until no visible change in its volume is observed.

The material’s compressibility index and Hausner ratio can then be calculated. Free flowing powders generally show little difference between the bulk and tapped densities.

Application: Tapped Density of Milk Powder


Not only is powdered milk a commonly used basic food item in situations where fresh milk is not available, but powdered infant formula is very important for infants and toddlers, either as supplementation to or as a substitution for breast feeding, especially for those cared for in a nursery. Infant formula needs to meet the nutritional requirements of children’s bodies by resembling the composition of breast milk through its special formulation. Experiments were carried out using two milk powder samples: an infant formula, suitable for the first six months of life, and a toddler formula, for kids above the age of one.

Tapped Density Test

The dried milk formulas were briefly stirred with a glass rod prior to adding it to the sample vessel using a funnel. For tapped density, 70 mL of milk powder was added to a 100 mL graduated cylinder and weighed prior to tapping. Using a Dual Autotap, the cylinder was lifted and dropped from a height of 3.0 mm for each tap (ASTM and USP standards).


The initial bulk densities for the milk powders were similar at 0.43 and 0.42 g/cm3 for infant and toddler powder formulas, respectively. After tapping with the Dual Autotap, they reached respective tapped densities of 0.56 and 0.55 g/cm3 . This change in density, following ASTM protocol, enabled calculations of their compressibility and Hausner ratio of 24.29 and 1.32 for the infant formula, and 25.0 and 1.33 for the toddler formula. These values are good for the dry state of milk powder to allow fairly easy handling for packing.


Anton Paar Application Note: D43IA022EN-B_Milk_Powder_Characterization_-_Chapter_2

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