Built a focussing system for the Eye H50 at work, that's used for hexane or hexene and bromium to show subtitution reactions.
The Narva NF80-in-a-can is a bit more powerful and also potentially overdriven a bit (though no blackening of the arc tube is visible despite a good 15 years of occasional use), but has no system to concentrate the light or use any light radiated from the back - so with a bit of luck, the reaction happens as fast with the tiny 50w lamp, as it does with the 80w one.