In the lab, Dr. Keen Bean gives Ritchie a formula that can eat through anything, in a toothpaste tube. If it can eat through anything, why doesn't it eat through the toothpaste tube it's in? I've seen this movie several times, and it irritates me every time I see it!
Inside the tube, it is lined with a special plastic that does not react with the acidic solution. I'm sorry, but I don't think you know anything about Science.