Determination of specific surface of powder - involves automatic weighing, compacting to standard volume, and determination of air flow resistance

摘要

An instrument for the automatic determination of the specific surface area of a powder operates by weighing a specific amount of material, shaking it to compact to a standard volume in a vertical column, and measuring its flow resistance to the passage of a fluid; a vibratory feed system feeds the powder to the sample tube which is mounted with the the compacting shaker on an arm pivoting about a horizontal axis; when the required weight is reached the feed is cut off by contacts and the compacting vibrator is switched on until the powder has sunk to the standard level in the cylinder, as detected by a photoelectric detector; the detector signal then energises a flow of air under pressure through the porous base of the vertical cylinder, and the flow resistance of the material in the column is determined in terms of the time needed for a given reduction in air pressure in the U tube.