The use of the hot-wire anemometer has been extended to include the measurement of temperature fluctuation level as well as temperature-velocity correlation, in a turbulent flow with heat transfer. Secondly, the hot wire can be used for the determination of mean relative concentration in the mixing of two gases of different known thermal characteristics. Finally, the instantaneous response of a hot wire in a turbulent flow with mixing of two gases of different thermal characteristics has been computed. This permits measurement of the concentration fluctuation level as well as the concentration-velocity correlation.