Nano- and Microtechnology from A - Z: From Nanosystems to Colloids and Interfaces

H

Hagen–Poiseuille Law

Poiseuille flow is the steady flow of incompressible fluid parallel to the axis of a circular pipe or capillary. The Hagen–Poiseuille law is an expression for the flow rate of a liquid in such tubes. It forms the basis for the measurement of viscosities by capillary viscometry.

Half-Colloid

See Lyophilic Colloid.

Half-Micelle

See Hemimicelle.

Hallikainen-Shell Sliding Plate

See Sliding Plate Method.

Hallimond Tube

A laboratory-bench-scale apparatus for conducting small-scale flotation tests. The Hallimond Tube comprises a glass cell covered by a porous frit which is in turn covered by a bent glass tube leading up and away from the frit. Just above the bend, there is a vertical collection tube leading downwards. A mineral slurry is kept in suspension above the frit while gas flows in and upwards through the frit so that bubbles stream upwards through the suspension. Hydrophobic particles will attach to the rising bubbles and be carried up and beyond the bend in the tube so that when the bubbles eventually break the floated particles sediment back downwards and are collected in the vertical collection tube. See also Froth Flotation.

Halo

In particle characterization, the false perimeter apparent in a particle image.

Halochromism

See Chromism.

Hamaker Constant

In the description of the London–van der Waals attractive energy between two dispersed bodies, such as particles or droplets, the Hamaker constant is a proportionality constant characteristic ...