ASTM D2717 Standard Test Method for Thermal Conductivity of Liquids
8. Procedure
8.1 Fill the cell with the sample until the liquid reaches a level of about 1 or 2 cm in the sidearm. Place it in the thermostated bath and allow to stand until thermal equilibrium is obtained. Determine equilibrium when the zero-current resistance of the cell reaches a constant value. Apply a higher (up to 30 mA) current to the cell and bridge circuit. Measure the magnitude of this current by monitoring the voltage drop across a 1-Ω resistor in series with the bridge. When the cell again reaches temperature equilibrium as determined by measurement of its filament resistance, measure the bath temperature accurately with a platinum resistance thermometer and take a final reading of cell resistance. Repeat this process at least three times for varying bridge currents. The results will usually show a trend with time at first. Continue measurements until the results are seen to be fluctuating about a mean. Take the final resistance measurements as the mean of readings taken with normal and reverse commutator settings in order that recorded resistances are the resistance of only the active portion of the cell filament and that the effects of the cell leads shall be cancelled. Calculate the temperature difference ΔT as the temperature difference between the cell wire temperature, determined from the cell resistance, and the temperature of the bath.
