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Theory
Saybolt viscometer is used for empirical measurement of viscosity of transparent and opaque lubricant and residual liquid oils, mostly electrical insulating oils of mineral origion at specified temperature. The viscometer is calibrated at regular intervals by measuring the efflux time at 100 F of viscosity standard. If efflux time differs from certified value by more than 0.2% then correction factor is calculated as F = V/t
Apparatus *Say bolt viscometer and bath *Withdrawal tube *Thermometer support *Filter funnel *Receiving flask *Timer (graduated in 10th of second and accuracy is 0.1% *when tested over 60-min intervals) *Viscosity thermometer *Bath thermometer
Procedure
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1) The sample was preheated below the flash point. 2) A cork stopper having a cord was inserted into the chamber at the bottom of viscometer to prevent the air escape. 3) The sample was filtered through 100 mesh screen directly into the viscometer until the level approached to the overflow rim. 4) The viscometer was constantly stirred by the thermometer for 1 min until the temperature become constant. 5) The oil was removed until its level reached just below the overflow rim with help of withdrawal tube. 6) °the receiving flask then was placed under the viscometer. At the same time, the timer was allowed to start as stopper was removed by cord until the flask filled to the mark. 7) The experiment was repeated at different temperatures.
Observations Initial temp. 20°C Final temp. 50°C Sr. No. 1 2 3 4
Temperature(°C)
Time(second)
20 30 40 50
2min-20sec 1min-24sec 1min-12sec 1min-5sec
Result:
Temperature and viscosity have inverse relation.