A New Capillary Viscometer for Small Amounts of Liquid and Its Application for Study on Viscocity of Blood

The apparatus used in experiment for the present study is a graduated glass tube closed at its top with its bottom end provided with two syringe needles held vertically. A negative pressure has been given through a glass tube by releasing a compressed rubber ball which is joined to the upper side of the tube. The air and the liquid to be tested are drawn in through the top and bottom capillaries respectively into the glass tube. The volume of the liquid thus drawn in measures the value of viscosity.The formula representing the relation of viscosity and the volume of the liquid drawn in has been determined. In practice, however, the relation has been experimentally determined by measuring the silicone oils with known viscosity. In the present apparatus the diameter and length of the upper capillary is 0.42 and 43mm, and the corresponding quality of lower capillary is 0.67mm and 78mm. The volume of the rubber ball compressed is 18cm3. The diameter and length of graduated glass tube are 4.6 and 65mm.A range of viscosity from 0.8 to 6.0 centipoise has been covered by this viscometer. The range of viscosity is varied by a suitable choice of dimensions of capillaries. The liquid rises to a certain level and then falls down due to the gravity. The highest level attained is used as the measure of viscosity in the above described calibration curve. The time for liquid flow until the highest level is around 5 seconds.The difference in density between blood and silicone oil produces only 4% error in the value of viscosity. The correction for the kinetic energy is about 3%.The error in reproducibility for the repeated measurements is about 1%. The rate of shear in the capillary wall is about 2×103 sec-1, which is in the same order as that for the actual blood flow in vessels. The volume of liquid required is only 0.3ml and the measuring time is less than 10 seconds.The viscosity of whole blood as a function of hematocrit and the viscosity of plasma as a function of protein content have been studied at a temperature of 37°C. The relation between the viscosities of whole blood and plasma and sedimentation rate has been investigated for a number of specimens of human blood.The viscosity of venous blood in a dog has been measured in vivo by inserting the pointed end of capillary of viscometer into the jugular vein where the intravenous pressure is almost zero. The variation of viscosity of blood in vivo with the injection of aqueous solution of glucose has followed.