Gradient Column Floats

What is a Density Gradient Column?

Density gradient columns can be used to determine the density of solid samples which are too small to be measured by pyknometry or hydrostatic weighing. A density gradient column is normally made in a glass tube between 750 and 1500 mm long and 35 to 60 mm diameter. It is mounted vertically in a water bath, and held at a constant temperature. The gradient is filled by mixing two miscible liquids, in constantly varying proportions as the column is filled.

Density Gradient Column Floats

Once the gradient has been formed, calibrated floats are lowered into the column. These will slowly sink until each reaches liquid of its own density. This allows a relationship for height up the column against density to be determined.

Quality Calibrated Glass Floats

H&D Fitzgerald’s calibrated Glass Floats are manufactured to the highest specifications and are calibrated traceably to recognised national standards of mass, density and temperature.

We offer a comprehensive service:

  • Floats are available within the density range of 650 to 2000 kg/m³ (0.65-2.00 g/ml) at 23°C.
  • We normally quote a uncertainty on our calibration certificates of ±0.15 kg/m³ at k=2, however our accredited Calibration and Measurement Capability (CMC) is ±0.1 kg/m³ at k=2 and, if necessary, we can issue a certificate with this uncertainty.
  • Each float has a unique identification number fused inside the glass, and is supplied with a calibration certificate under our ISO 17025 accreditation, quoting its density and mass.
  • We offer a recalibration service for both our own floats and any floats made by other manufacturers, as long as they can be uniquely identified.

For detailed pricing information and instructions on how to order, see Ordering Gradient Column Floats.