off topic, but glycerine (same thing as glycerol and glycerin) isn't a thermometer and the most common known thing glycerine is used in is dynamite (not purely but as a compound). Glycerine itself though is a viscous liquid that is used in medications, as a lubricant (and when added to dishsoap and water to make bubbles makes the bubbles less likely to pop easily).
Also it's sweet tasting
edit:
@Nick I realized what you were talking about with thermometers, but glycerine is clear. it is used as a filler to avoid air bubbles in some thermometers. I suppose it could be colored though but it doesn't work like mercury for the actual part that rises
edit2:
By itself glycerine is not flammable