Dilatometer

A dilatometer is a scientific instrument that measures volume changes caused by a physical or chemical process. A familiar application of a dilatometer is the mercury-in-glass thermometer, in which the change in volume of the liquid column is read from a graduated scale. Because mercury has a fairly constant rate of expansion over ambient temperature ranges, the volume changes are directly related to temperature. A dilatometer is a scientific instrument that measures volume changes caused by a physical or chemical process. A familiar application of a dilatometer is the mercury-in-glass thermometer, in which the change in volume of the liquid column is read from a graduated scale. Because mercury has a fairly constant rate of expansion over ambient temperature ranges, the volume changes are directly related to temperature. Dilatometers have been used in the fabrication of metallic alloys, study of martensite transformation, compressed and sintered refractory compounds, glasses, ceramic products, composite materials, and plastics. Dilatometry is also used to monitor the progress of chemical reactions, particularly those displaying a substantial molar volume change (e.g., polymerisation). A specific example is the rate of phase changes. Another common application of a dilatometer is the measurement of thermal expansion. The thermal expansivity is defined as: α = 1 V ( ∂ V ∂ T ) p , N   {displaystyle alpha ={frac {1}{V}}{iggl (}{frac {partial V}{partial T}}{iggr )}_{p,N} }