Abstract
Among various methods of viscosity measurement, the capillary methods are the most usual ones, by which the coefficient of viscosity is obtained on the assumptions that there is no slip at the capillary wall and that the fluid is homogeneous throughout the capillary, and so on.
So it is important to study first of all whether these assumptions hold or not in the actual flow. As regards the wall effect, measurements of the flow of various liquids using capillaries of different materials have hitherto been reported, but some of them are of doubtful accuracy and ambiguous in details of their experiments.
To obtain systematic and accurate data on this problem, measurements were made of efflux time of ion-exchanged water, human blood and plasma, using an Ostwald type viscometer with and without paraffine coating.
Correction in the thickness of the paraffine layer was made based on the Hagen-Poiseuille equation. Moreover, the change of the efflux time with the time elapsed was measured by using another capillary at the same time as shown in Figs. 1 (B) and 2 (B) to correct the effect due to denaturation of the samples such as blood and plasma.
The result shows that the efflux time is slightly increased by the paraffine coating and the order of the increase is as follows: water (-0.92∼+1.64%)<plasma(+0.15∼+2.54%)<blood(-0.56∼+4.2%).
