Gas Mixing, Calibration, and Permeation

Question 1

What three things does the permeation rate from a permeation tube depend on and which one
is controllable once purchased?

Answer 1

1) Temperature (controllable)
2) Permeable wall (purchased at a certain length)
3) The chemical

Question 2

Explain why it is essential to keep the oven temperature for a permeation tube to within
±0.1°C.

Answer 2

Permeation is very sensitive to temperature

Question 3

What two phases of a compound must be present in a permeation tube and how is the
permeation rate affected as the compound is used up?

Answer 3

The compound must be at equilibrium with its liquid and gas phase inside the tube and the permeation rate will not be affected until all liquid is used up

Question 4

What is the tube or sleeve of the permeation tube, that is used to generate calibration gas,
usually made of?

Answer 4

Teflon

Question 5

Explain why an analyzer whose sample cell is at atmospheric may give different readings for
the exact same concentration of a sample on different days. In addition, explain how this
problem could be mitigated.

Answer 5

The concentration of the chemical in a certain volume will change if temperature and atmospheric pressure changes in the sample.

To mitigate this a correction equation is used to obtain a true concentration.