The author replies to Lunelli.The article by Lee et al. (1) was based on understanding the concept of the partial pressure for undergraduate students rather than the gas permeability of polymers. That experiment showed obviously that the partial pressures of each molecule in a helium-inflated balloon are changed over time although the total pressure of the balloon inside is higher than outside. To understand this natural phenomenon, we proposed a tiny-hole model to explain that the partial pressures of nitrogen and oxygen are dramatically increased with time. This model is inadequate to explain a real permeation phenomenon but adequate to explain that the driving force for the equilibrium between inside and outside of balloon is the difference of partial pressures. I expect that undergraduate students can learn what causes the helium-inflated balloon to fall in a few days through the proposed experiment. If the students have background regarding interactions between polymers and molecules, permeation phenomena could be well explained. Under these circumstances, the comments of B. Lunelli could be of importance.The result reported in J. Chem. Educ. (1) was obtained by using latex balloons purchased from Aldrich. Also, we tried various latex balloons that we purchased in general stationery stores and got results similar to those reported in the article. Literature Cited- Lee, J.-Y.; Yoo, H.-S.; Park, J. S.; Hwang, K.-J.; Kim, J. S. J. Chem. Educ. 2005, 82, 288.
|
Citation
