Normal glass bead columns

The density gradient column is now widely used and necessitates observing the level to which a test specimen will sink in a column of liquid, the density of which increases uniformly from top to bottom. The column should be about 40-50 mm I/D and normally graduated from 0 at the top to 100 cm at the bottom. Up to three such columns can be positioned in a water bath controlled at 23 1°C. A valuable attribute of this method is that the columns, when prepared, can be accurately calibrated with glass beads of known density. 

---