| MadSci Network: Chemistry |
The question posed by Bob:
I have seen a demonstration of chemical incompatibility using a
Styrofoam(R) cup, hot coffee, and white correction fluid. The 1,1,1
TCA (I am assuming) in the fluid will eventually dissolve through the
cup, but never so fast as when poured into a cup already filled with
coffee. [Why]?
Dear Bob,
Your question is really interesting. A number of chemists have been asked to try to explain the phenomenon, but noone so far has been able to offer an explanantion. I would suggest asking this question to the Usenet group sci.chemistry. This way, you can easily contact a large number of chemists.
At this time, we cannot offer a direct answer to your question. In lieu of answering your question, I would like to offer you a couple of experimental observations. I took some cold coffee that had been sitting in the pot overnight, and I filled two styrofoam cups about halfway. I also filled two cups with water,and left one standing empty. I took one of the coffee cups and one of the water cups and heated them to boiling in the microwave. The cups were left standing for 2 minutes. I then added 3-5 drops of correction fluid (Liquid Paper in this case) to all of the cups. In under a minute, holes developed in the bottoms of the cups that contained hot coffee and hot water. The holes appeared where the correction fluid had settled to the bottom. The cups with cold liquids never developed holes in bottoms, despite being allowed to stand for over an hour. Likewise, the cup with just liquid paper did not develop a hole.
Summary of results:
Solvent: Result Hot coffee The cup developed holes. Cold coffee No holes. Hot water The cup developed holes. Cold water No holes. None No holes.So it appears that the critical parameter is heat, not coffee. If you want to carry the experiment further, you might do some experiments to determine what the minimum temperature is for hole development. You might also try some other solvents such as alcohol, lemon juice, etc....
As far as the mechanism, I have no idea. My speculation could run on endlessly. I have tried in the past to find out what the ingredients to this sort of correction fluid are, but I have failed. Maybe the information is now available, or maybe I just missed it somehow. I think that the next step is to determine all the ingredients in correction fluid, and propose a mechanism based on this information.
Thanks for your question, I was happy to have an excuse to do a fun experiment.
Dave
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