One way to measure the viscosity coefficient is to use Ostwald viscometer. Firstly, castor oil is heated to a certain temperature to reach a stable temperature. Then a predetermined amount of castor oil is added to the viscosity tube of the viscometer, and the distance that castor oil flows through the viscosity tube is calculated by time. The viscosity coefficient can be calculated according to the flow time and pipe diameter.
Specifically, assuming that the density of castor oil is ρ, the radius of viscosity tube of viscometer is r, the volume of castor oil added into viscometer is v, and the flowing time is t, the viscosity coefficient η of castor oil can be calculated as follows:
η = ρVgr^2/ (9ηt)
Where g is the acceleration of gravity.
It should be noted that the viscosity coefficient of castor oil will change at different temperatures, so when measuring the viscosity coefficient, it is necessary to strictly control the temperature and take the average value for several times in a certain temperature range.
When using Ostwald viscometer to measure viscosity coefficient, it is necessary to choose different viscosity tubes according to the viscosity characteristics of castor oil to ensure the accuracy of measurement. At the same time, both viscometer and castor oil need to be heated to a certain temperature before measurement, so as to eliminate the influence of temperature on the measurement results.