10. Procedure
10.1 Thoroughly clean and dry the cup and outlet tube of the viscosimeter as described in 9.1.1 and insert the stopper. Fill the outer bath and bring it to the required temperature of test. Maintain the bath not more than 1°C high for tests at 25°C, 40°C, or 50°C, and not more than 2 or 3°C high for tests at 100°C.
10.2 Pour the material into the cup until it exactly reaches the tops of the three measuring points when the instrument is level. Position the 50 mL testing flask so that the bottom of the flask is 130 ± 5 mm below the discharge end of the efflux tube, and adjust it so that the effluent will strike the narrow portion of the neck of the flask near or slightly below the calibration line.
10.3 Place the lid and inner thermometer into position and maintain the bath, with frequent agitation, at such a temperature that the material in the viscosimeter cup remains at the test temperature. Maintain these conditions for 3 min. Check the accuracy of the temperature reading by holding the stopper firmly in position and rotating the cover at short intervals during the first 2 min, but do not disturb the material during the last minute. When these conditions have been met, withdraw the stopper from the efflux tube, simultaneously start the timer, and suspend the stopper by the hook on the cover. Determine the time in seconds for 50 mL of material to flow from the viscosimeter.
NOTE 2 - Once the material has started to flow through the efflux tube, do not use the ring burner, but maintain the required temperature by the addition or removal of water at suitable temperatures, or by an auxiliary burner momentarily directed at the outside cylindrical portion of the water jacket.
11. Calculation
11.1 Calculate the Engler specific viscosity by dividing the time of flow for 50 mL of material at the selected temperature by the factor, as previously determined, according to the following formula:
where:
t = selected temperature of test, °C.
12. Precision and Bias
12.1 Results should not differ from the mean by more than the following amounts:
13. Keywords
13.1 tar; engler specific gravity