[kicl]

Does anyone know how to liquefy a small quantity of chlorine gas and seal it in an
ampoule for an element collection?

[ATMyller]

With a cold finger cooled in liquid nitrogen bath. Maybe a dry ice/propanol bath could do as well, but I'd recommend use of liquid nitrogen to make it solid.

The problem is you'll need storage the ampoule on dry ice or the chlorine will boil and could blow up the ampoule. Unless it's a very small amount in a rather large vacuumed ampoule.

[Borek]

I was surprised to find out that crtitical point of chlorine is above 400 K, so could be that at room temperature pressure will be not that high - or at least it will be low enough that glass ampoule of reasonable strength and price can be found.

Even than I am not sure I would be interested in keeping liquid chlorine at home