The sensor is just the mercury, a liquid metal.
Mercury is poisonous.
It could be used to do this - it is capable of doing it. However, Mercury is poisonous and a mercury thermometer is made out of fragile glass. Thus the danger that the thermometer would break releasing mercury into the milk (which would be for a person to drink) means that a mercury thermomiter is not the temperature sensor to use in this instance.
volume of the mercury
what do they use for the liquid in glass ball thermometer
mercury
German physicist Daniel gabriel Fahrenheit invented the mercury-in-glass thermometer
The capillary tube of the thermometer ( in case of a mecury thermometer).
The red liquid in a thermometer is Mercury, which is usually encased in a glass tube
For a classic thermometer: glass and mercury, colored ethanol or another liquid.
"thermal expansion"
either mercury or alcohol