ASTM D1665 Test Method for Engler Specific Viscosity of Tar Products
8. Preparation of Sample
8.1 Stir the sample until it is homogeneous, using heat if necessary. Avoid inclusion of air bubbles, loss of volatile or other effects, which may influence the viscosity. Strain a representative portion of the sample through the strainer to eliminate particles, and proceed in accordance with Section 10. Strain the material directly into the viscosimeter if preferred.
9. Standardization and Calibration of Viscosimeter
9.1 The efflux time for 200 mL of distilled water at 20.0°C with an acceptable Engler viscosimeter shall be between 50.0 and 52.0 s. Determine this time and the factor representing the efflux time for 50.0 mL of water at 25.0°C, as described in 9.1.1-9.1.6:
9.1.1 Clean the inner vessel and efflux tube of the viscosimeter with appropriate solvents, and finish by washing several times with pure methyl or 95 % ethyl alcohol and rinsing several times with distilled water.
NOTE 1 - In cleaning the viscosimeter take particular precautions to avoid injury to the efflux tube and measuring points. Use only a soft cloth in the cup, and soft tissue in the efflux tube. Avoid wires or similar substances and corrosive liquids. To prevent an air seal, keep the lid and lip of the cup clean at all times. After a viscosimeter has been used with bituminous materials, pay particular attention to cleaning the metal surrounding the bottom end of the efflux tube. Failure to do this may cause erratic and erroneous results.
9.1.2 Immediately after cleaning the viscosimeter, close the efflux tube with a stopper which has never been in contact with tar, oil, or similar materials. Fill the outer bath with water at slightly below or above 20°C as found necessary to maintain the inner temperature at 20°C. Fill the inner vessel approximately to the top of the fixed gage points with freshly boiled distilled water at 20.0°C. Level the instrument so the tips of the gage points lie in a plane parallel to the surface of the water, and add or remove water with a pipet until its surface is even with the extreme tips of all gage points. Place the lid and thermometer in position and maintain the inner temperature at 20.0°C for at least 3 min with frequent stirring; agitate the contents of the inner cup by holding the stopper firmly and rotating the cover back and forth and around, occasionally stirring the outer bath. Dry the bottom of the efflux tube and the area surrounding it by wiping. Carefully lift the stopper until water runs into and completely fills the efflux tube, and adjust until a hemispherical drop about 4.5 mm in diameter hangs from and covers the lower end of the tube. Then allow to stand without agitation for 1 min.
9.1.3 Place a dry calibration flask 240 ± 10 mm below the discharge end, and adjust it so the flow will strike the narrow portion of the neck of the flask near or slightly below the calibration line. Start the timer and simultaneously withdraw the stopper, suspending it by the lid hook. Determine the time, in seconds, for flow of 200 mL. Repeat this determination, starting the flow under conditions described above until at least three successive determinations, varying not more than 0.2 s, are obtained. If the results obtained from three or more tests do not check within 0.2 s, clean the viscosimeter again and make additional trials, until three or more results agree within 0.2 s.
9.1.4 Make another series of determinations as above, starting with the instrument freshly washed with alcohol, then with distilled water and refilled as before. The average results from the second series shall agree with the average from the first series within 0.2 s. Take the efflux time for 200 mL at 20.0°C as the mean of the averages of at least two series of determinations agreeing within 0.2 s. This time for an acceptable viscosimeter shall be between 50.0 and 52.0 s.
9.1.5 Make additional runs as necessary, beginning with a newly cleaned viscosimeter until two successive series are in substantial agreement.
9.1.6 The factor representing efflux time for 50 mL of water at 25.0°C has been found to be equivalent to the efflux time for 200 mL of distilled water at 20.0°C multiplied by 0.224.
