Diffusion tube

Generating
calibration gas with a diffusion tube

A diffusion tube is a
glass tube that consists of a liquid containing portion and a diffusing portion
with a uniform inner diameter. A pure target liquid is put into the liquid
container using a glass syringe. The liquid must have a vapour pressure of 5 to
400 mm Hg at 25 to 50ºC (77 to 122ºF) and be highly stable. If this tube is
kept at a constant temperature, the liquid evaporates and diffuses at a
constant rate.

*1 Although
not a common application, gases of substances that are solid at normal temperatures
can be generated using gas diffusion tubes. Please contact your licensed GASTEC
representative for information regarding specific substances.

*2 This
method cannot be applied to substances with extremely high or low vapour
pressure or substances with decomposability, corrosiveness, hygroscopicity or
polymerizability due to their diffusion rate not being constant.

Diffusion tube

[No.3100]

Suitable for continuous generation of single
component gases for calibration over sustained periods of time.

Diffusion tube for
multiple components

[No.3200]

Solvents such as thinner contain multiple
components. Previous models permit the generation of single component gases
for calibration purposes. However, a multiple component type diffusion tube
enables the simultaneous generation of 4 types of gases for calibration.
Employing this tube enhances analytical testing.