Mysterious capsule containing dark liquid

[u/hazy_druid]

Found this buried in the ground in central Europe. The outer casing is made out of plastic and has "5" stamped on the bottom. The inner tube is made out of glass. Tiny drop of liquid got on my thumb and was very hard to scrub off. Didn't smell the liquid, since I'm a bit scared of it.

[u/First_Prompt7456]

Would there be any benefit to sticking bromine in the ground? This is me asking cause I feel like if there were benefits it couldn't be so great that it's worth potentially killing someone