Thermal conductivity electrons. In this case the mean velocity is the Fermi velocity which is temperature independent. The mean free path is determined by the impurities and the crystal imperfections which are temperature independent as well. So the only temperature-dependent quantity is the heat capacity "c", which, in this case, is proportional to "T". So with "k" a constant. For pure metals such as copper, silver, etc. "l" is large, so the thermal conductivity is high. At higher temperatures the mean free path is limited by the phonons, so the thermal conductivity tends to decrease with temperature. In alloys the density of
Electrical conductivity meter develop a model to calculate concentration of the liquid. Concentration of pure liquids can be calculated when the conductivity and temperature is measured. The preset curves for various acids and bases are commercially available. For example, it is possible to measure the concentration of high purity hydrofluoric acid using conductivity based concentration measurement [Zhejiang Quhua Fluorchemical, China Valmet Concentration 3300]. Benefit of conductivity and temperature based concentration measurement is the superior speed of inline measurement compared to on-line analyzer. Conductivity based concentration measurement has limitations. The concentration-conductivity dependence of most acids and bases is not linear. Conductivity based measurement can’t