Science Buddies: "Ask an Expert"

Hi,
I am getting ready to test the porosity of eggshells. Before selecting the project, I mixed a little chlorine in an egg white to be sure that I had a reliable test for chlorine and I soaked an egg in bleach to be sure that my test would pick up small amounts of chlorine that entered the egg. Now that I am ready to begin my experiment, I am not able to detect any chlorine no matter what the concentration of bleach. I am not sure what was working before that is not working now. Could it have something to do with the age of the eggs?

Hi,

I don’t know what the exact molecular weight exclusion limit for eggshells is, but eggshells are porous to small molecules like oxygen, carbon dioxide, and water vapor, which are 32, 44, and 18 Daltons, respectively. Bleach is sodium hypochlorite NaClO, 74 Daltons, so is slightly larger so perhaps this molecule is too large to diffuse through the eggshells.

Here are some questions that might help explain your results. How did you measure the chlorine in your initial trial? Are you using chlorine or sodium hypochlorite? Did you change brands of bleach? Are you using fresh eggs or boiled eggs? Were there any other differences in the method you are using now and during the trial?

Here is a science buddies project on eggshell porosity that is based on water. Perhaps you could adapt your project and use an increase in weight to measure your results. You would need a very accurate balance to do this experiment.

https://www.sciencebuddies.org/science- ... p046.shtml

Donna Hardy