What Is The Red Liquid In A Thermometer. If your thermometer is filled with a red liquid, your thermometer contains red dyed alcohol or mineral spirits and not mercury. The expansion and contraction of this mercury size are then further increased in the thin bore of the glass tube.
What happens to the red liquid in a thermometer? Although uncommon in modern thermometers, a clear color indicates water. Since these are transparent the liquid is made more visible by the addition of a red or blue dye.
