Since my camera is not working really well, I could only record this two horrible quality gif from a new fluorescent thermochromic compound.

It is a mixture of two compounds, one emits yellow color at room temperature under UV light and the other one that emits a faint green color. When they are at liquid nitrogen temperature (−195.79 °C; 77 K; −320 °F) they both emit a blue color. When they are heated up to room temperature, they change color at different temperature as seen on the gifs.


How to do it: cryogenic distillation. 

What is cryogenic distillation? A flask with compounds and a volatile solvent in it in connected to a tube what ends in a liquid nitrogen cooled trap while the whole system is closed. The volatile solvents (in this case dichloromethane) distills out from the room temperature flask and condenses into the −196 °C (77 K; −321 °F) cold liquid nitrogen trap. When all solvents are removed the product is left behind (hopefully crystals at the bottom of the flask) what was previously dissolved in the solvent.

Why is a balloon at the end of the whole system? It there would be no balloon or the system would be open to the atmoshere, the nitrogen trap would condense liquid oxygen and dry ice into the trap and not the solvent what we are want. The other reason is, that if the system would be closed, any external pressure would be “trapped” inside what could cause serious problems.