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.