A thermometer for measuring small changes of temperature.
It consists of a mercury-in-glass thermometer with
a scale covering only 5 or 6°C. Calibrated in hundredth
of a degree. It has two mercury bulbs, the range of
temperature to be measured is varied by running mercury
from the upper bulb into the larger lower bulb.
It is used particularly for measuring depression of freezing
point or elevation of boiling point of liquids when
solute is added, in order to find relative molecular