Thermodynamic properties of any material or solution are valuable not only for estimating the usefulness of the material or the feasibility of reactions in solution, but they also provide one of the best methods for investigating theoretical aspects related to the material or solution structure. Thermal properties of materials can be measured directly or indirectly. This includes temperature, developed pressure, calorimetry, and thermal conductivity. The measurements are made with a thermodynamic instrument, which is any device that allows for quantitative measurement. The reservoir and the meter are both thermodynamic instruments: