Materials and Methods Samples investigated consisted of high molecular weight xanthan in polished water. Xanthan was a gift from W. F. Reed, Dept. of Physics, Tulane University. By maintaining a constant flow rate for a given capillary tube, a measurement of the pressure drop along the capillary tube can be converted into a measurement of viscosity. Further, if Eq. 1 holds and the response of the pressure transducer is linear, a direct measurement of the specific viscosity can be effected without the need for a calibration of the device. This is a significant advantage of the single capillary design.
V is the voltage read from the pressure transducer.
Note that any calibration constants will cancel in the ratio. The flow of a viscous fluid past a fixed surface will result in shear flow. The shear is clearly greatest at the pipe wall and goes to zero at the center. Figure 1 - Reduced viscosity of xanthan as a function of concentration for varying degrees of shear. Results and Discussion Reduced viscosity results are shown in Fig. 1.