tenex glue

Yes that stuff is hot and volatile. 

I've been using Tenex for years and love it. It evaporates quickly if left open but not much at all if the bottle is tightly closed so I'd suspect you have an air leak somewhere. In the hobby store I once saw several new bottles in the box display that were far from full and pointed it out to the owner. He was able to tigten each one a bit and said he'd seen that before although it wasn't common. As an aside, I once knocked over an open bottle and have come close several other times so I now pour it into an empty Tamiya cement bottle because it's large square shape is far less likely to tip if bumped plus it has a brush built into the cap.