ASTM D4486 Test Method for Kinematic Viscosity of Volatile and Reactive Liquids
10. Procedure for Kinematic Viscosity
10.1 Maintain the bath at the test temperature within the limits given in 6.1. Apply the necessary corrections, if any, to all thermometer readings.
10.2 Select a clean, dry, calibrated viscometer that will give a flow time not less than the minimum specified for the viscometer (see Table 3), or 200 s, whichever is the greater.
10.3 Charge the viscometer through Tube A (see Fig. 1) until Bulb B is half filled.
10.4 Test samples that are not stable in the presence of air at the test temperature must have the air in the viscometer purged by a working gas that does not react with the test sample.
10.4.1 For the vulnerable-liquid viscometer (Fig. 1), attach Tube A to a controlled source of a working gas. Tilt the charged viscometer until the liquid sample no longer covers the end of Tube C. Pressure purge the viscometer with working gas. Release the pressure and repeat the purge at least four times.
10.4.2 Multiple purges are not required in the case of vulnerable samples that are volatile but stable in the presence of air at the test temperature.
10.5 Adjustment of Pressure:
10.5.1 In the vulnerable-liquid viscometer, adjust the pressure in the viscometer to the predetermined test pressure.This pressure may be equal to the ambient in the case of reactive samples or it may be an elevated pressure sufficient to repress the boiling of a volatile sample. In any case the pressure inside the viscometer must not be permitted to exceed 2 x 10(-5) kPa. (2 atm).
10.6 Mount the viscometer in the viscometer holder, and place assembly in the constant-temperature bath. Ensure that the Working Capillary D is held vertical. Allow the charged viscometer to remain in the bath long enough to reach the test temperature. Because this time may vary with the viscosity of the sample and test temperature, establish a safe temperature equilibrium time by trial.
10.7 Fill the timing Bulb F with sample as follows: Increase the pressure in the viscometer by an amount sufficient to force the sample upward through Tubes D and E to fill Bulb F entirely and Bulb G partially. Since the inside diameter of Tube E is greater than that of Tube D, Bulb F is filled mainly by liquid that flows through Tube E and Bulb G. Restore the pressure in the system to the prechecked test pressure. As this is done the sample begins to drain from the capillary and upper bulbs of the viscometer. Tubes E and C are sufficiently large in a diameter that they drain completely before the liquid level in Bulb G reaches the upper timing mark.
10.8 With the sample flowing freely, measure in seconds, to within 0.2 s (see section 6.7), the time required for the meniscus to pass from the first timing mark to the second. If this flow time is less than the specified minimum (see 10.2) select a viscometer with a capillary of smaller diameter and repeat the operation.
10.9 Repeat the procedure described in 10.7 and 10.8 to obtain a second determination of the flow time. If the two measurements agree with 0.4 % use the average for calculating the reported kinematic viscosity. If the required agreement is not obtained, reject the results and repeat the test.
10.10 Clean the viscometer as described in Section 9.
