ASTM D971 for Interfacial Tension of Oil Against Water by the Ring Method
7. Preparation of Apparatus
7.1 Glass containers can be cleaned by rinsing in xylene, hexane or another suitable hydrocarbon solvent, followed by a rinse in acetone or methyl ethyl ketone. Following these rinses they can be cleaned using detergent in hot water and rinsed thoroughly with tap and then distilled water. Dry the glass vessel if not for immediate use.
7.2 The ring should be cleaned by immersing it in a small container of xylene, hexane or another suitable hydrocarbon solvent for at least 5 s while spinning the ring back and forth. Next, repeat this rinse using a container filled with acetone or methyl ethyl ketone. Flame the ring in a gas flame, again spinning it to obtain rapid, uniform heating. The ring should barely glow orange and should be heated for no more than 5 s. Clean the ring immediately before each measurement.
7.3 The tensiometer should be leveled by placing a bubble level device on the sample platform, if not equipped with one, and adjusting the tensiometer base until the platform is level.
8. Calibration of Apparatus
8.1 Calibrate the tensiometer against known weights and adjust its zero point according to the procedure of its manufacturer. Make certain that all portions of the ring are in the same horizontal plane.
